ORCID Profile
0000-0001-5060-779X
Current Organisation
University of Tasmania
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Oceanography | Chemical Oceanography | Palaeoclimatology | Biological Oceanography | Physical Oceanography | Physical Geography and Environmental Geoscience | Quaternary Environments | Ecological Applications | Inorganic Geochemistry | Geomorphology and Regolith and Landscape Evolution | Glaciology | Geochronology | Isotope Geochemistry | Climate Change Processes | Ecological Impacts of Climate Change | Environmental Chemistry (incl. Atmospheric Chemistry) |
ANZSRC Socio-Economic Objective (SEO)
Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Expanding Knowledge in the Earth Sciences | Physical and Chemical Conditions of Water in Marine Environments | Climate Change Models | Antarctic and Sub-Antarctic Oceanography | Ecosystem Adaptation to Climate Change | Ecosystem Assessment and Management of Fresh, Ground and Surface Water Environments | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Climate Variability (excl. Social Impacts) | Global Effects of Climate Change and Variability (excl. Australia, New Zealand, Antarctica and the South Pacific) (excl. Social Impacts) | Expanding Knowledge in the Environmental Sciences | Ecosystem Assessment and Management of Marine Environments
Related Links
Publications
Marine nitrogen fixers mediate a low latitude pathway for atmospheric CO2 drawdown
Publisher: Springer Science and Business Media LLC
Date: 10-10-2019
DOI: 10.1038/S41467-019-12549-Z
Abstract: Roughly a third (~30 ppm) of the carbon dioxide (CO 2 ) that entered the ocean during ice ages is attributed to biological mechanisms. A leading hypothesis for the biological drawdown of CO 2 is iron (Fe) fertilisation of the high latitudes, but modelling efforts attribute at most 10 ppm to this mechanism, leaving ~20 ppm unexplained. We show that an Fe-induced stimulation of dinitrogen (N 2 ) fixation can induce a low latitude drawdown of 7–16 ppm CO 2 . This mechanism involves a closer coupling between N 2 fixers and denitrifiers that alleviates widespread nitrate limitation. Consequently, phosphate utilisation and carbon export increase near upwelling zones, causing deoxygenation and deeper carbon injection. Furthermore, this low latitude mechanism reproduces the regional patterns of organic δ 15 N deposited in glacial sediments. The positive response of marine N 2 fixation to dusty ice age conditions, first proposed twenty years ago, therefore compliments high latitude changes to lify CO 2 drawdown.
Evidence from authigenic uranium for increased productivity of the glacial Subantarctic Ocean
Publisher: American Geophysical Union (AGU)
Date: 10-2001
DOI: 10.1029/2000PA000542
Compiled Southern Ocean sea surface temperatures correlate with Antarctic Isotope Maxima
Publisher: Elsevier BV
Date: 03-2021
Assessing the influence of ocean alkalinity enhancement on a coastal phytoplankton community
Publisher: Copernicus GmbH
Date: 21-01-2022
DOI: 10.5194/BG-2022-17
Abstract: Abstract. Ocean alkalinity enhancement (OAE) is a proposed method to counteract climate change by increasing the alkalinity of the surface ocean and thus the chemical storage capacity of seawater for atmospheric CO2. The impact of OAE on marine ecosystems, including phytoplankton communities which make up the base of the marine food web, are largely unknown. To investigate the influence of OAE on phytoplankton communities we enclosed a natural plankton community from coastal Tasmania for 22 days in nine microcosms during a spring bloom. Microcosms were split into three groups, (1) the unperturbed control, (2) the unequilibrated treatment where alkalinity was increased (+495 ± 5.2 µmol/kg) but seawater CO2 was not in equilibrium with atmospheric CO2, and (3) the equilibrated treatment where alkalinity was increased (+500 ± 3.2 µmol/kg) and seawater CO2 was in equilibrium with atmospheric CO2. Both treatments have the capacity to increase the inorganic carbon sink of seawater by 21 %. We found that simulated OAE had significant but generally moderate effects on various groups in the phytoplankton community and on heterotrophic bacteria. More pronounced effects were observed for the diatom community where silicic acid draw-down and biogenic silica build-up were reduced at increased alkalinity. Observed changes in phytoplankton communities affected the temporal trends of key biogeochemical parameters such as the organic matter carbon-to-nitrogen ratio. Interestingly, the unequilibrated treatment did not have a noticeably larger impact on the phytoplankton (and heterotrophic bacteria) community than the equilibrated treatment, even though the changes in carbonate chemistry conditions were much more severe. This was particularly evident from the occurrence and peak of the phytoplankton spring bloom during the experiment, which was not noticeably different from the control. Altogether, the inadvertent effects of increased alkalinity on the coastal phytoplankton communities appear to be justifiable, relative to the enormous climatic benefit of increasing the inorganic carbon sink of seawater by 21 %.
Global, regional, and national incidence, prevalence, and years lived with disability for 354 diseases and injuries for 195 countries and territories, 1990–2017: a systematic analysis for the Global B
Publisher: Elsevier BV
Date: 11-2018
Distribution and variability of iron input to Oregon coastal waters during the upwelling season
Publisher: American Geophysical Union (AGU)
Date: 09-09-2005
DOI: 10.1029/2004JC002590
Assessing the influence of ocean alkalinity enhancement on a coastal phytoplankton community
Publisher: Copernicus GmbH
Date: 12-2022
Abstract: Abstract. Ocean alkalinity enhancement (OAE) is a proposed method to counteract climate change by increasing the alkalinity of the surface ocean and thus the chemical storage capacity of seawater for atmospheric CO2. The impact of OAE on marine ecosystems, including phytoplankton communities which make up the base of the marine food web, is largely unknown. To investigate the influence of OAE on phytoplankton communities, we enclosed a natural plankton community from coastal Tasmania for 22 d in nine microcosms during a spring bloom. Microcosms were split into three groups, (1) the unperturbed control, (2) the unequilibrated treatment where alkalinity was increased (+495 ± 5.2 µmol kg−1) but seawater CO2 was not in equilibrium with atmospheric CO2, and (3) the equilibrated treatment where alkalinity was increased (+500 ± 3.2 µmol kg−1) and seawater CO2 was in equilibrium with atmospheric CO2. Both treatments have the capacity to increase the inorganic carbon sink of seawater by 21 %. We found that simulated OAE had significant but generally moderate effects on various groups in the phytoplankton community and on heterotrophic bacteria. More pronounced effects were observed for the diatom community where silicic acid drawdown and biogenic silica build-up were reduced at increased alkalinity. Observed changes in phytoplankton communities affected the temporal trends of key biogeochemical parameters such as the organic matter carbon-to-nitrogen ratio. Interestingly, the unequilibrated treatment did not have a noticeably larger impact on the phytoplankton (and heterotrophic bacteria) community than the equilibrated treatment, even though the changes in carbonate chemistry conditions were much more severe. This was particularly evident from the occurrence and peak of the phytoplankton spring bloom during the experiment, which was not noticeably different from the control. Altogether, the inadvertent effects of increased alkalinity on the coastal phytoplankton communities appear to be rather limited relative to the enormous climatic benefit of increasing the inorganic carbon sink of seawater by 21 %. We note, however, that more detailed and widespread investigations of plankton community responses to OAE are required to confirm or dismiss this first impression.
Detection, dispersal and biogeochemical contribution of hydrothermal iron in the ocean
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/MF16335
Abstract: This review aims to bring into focus the current understanding of hydrothermal systems and plume dynamics, tracers of hydrothermalism and the contribution of iron from hydrothermal vents to the global oceanic iron budget. The review then explores hydrothermal effect on surface ocean productivity. It is now well documented that scarcity of iron limits the production of chlorophyll-producing organisms in many regions of the ocean that are high in macronutrients. However, it is only recently that hydrothermal inputs have gained recognition as a source of Fe to the deep oceans that may potentially affect surface ocean productivity in some regions. A compilation of iron measurements from hydrothermal vents reveals that although hydrothermal studies measuring iron have increased significantly in recent years, there is still a dearth of data below 40°S. New analytical approaches for tracing iron sources, coupled with increasing s ling coverage of the oceans, is quickly improving knowledge of the effect of hydrothermal sources on biogeochemical cycles, a vital component in predicting future climate scenarios.
Effects of rabeprazole sodium on gastric emptying, electrogastrography, and fullness
Publisher: Springer Science and Business Media LLC
Date: 2003
Abstract: Proton pump inhibitors have been reported to delay gastric emptying, but this effect is controversial. Our aim was to determine the effect of rabeprazole sodium on several parameters of gastric function including gastric emptying, myoelectrical activity and ingested water volume required to produce fullness. Fifteen healthy males underwent assessment of solid-phase gastric emptying with the [13C] Spirulina platensis breath test as well as electrogastrography and satiety testing using a 5-min water load. Subjects were evaluated at baseline, after administration of placebo, and after rabeprazole sodium 20 mg daily for one week. No significant differences were seen between groups with respect to solid-phase gastric emptying as measured by T1/2 or T(lag). No differences were seen between baseline, placebo, and rabeprazole with respect to the number of normal electrogastrograms and the volume of water required to produce fullness. In conclusion, one week of therapy with rabeprazole sodium does not significantly alter gastric emptying, myoelectrical activity or threshold to fullness.
Increased glacial-age ventilation of the Chilean margin by Antarctic Intermediate Water
Publisher: Springer Science and Business Media LLC
Date: 13-12-2010
DOI: 10.1038/NGEO715
The Sensitivity of the Antarctic Ice Sheet to a Changing Climate: Past, Present, and Future
Publisher: American Geophysical Union (AGU)
Date: 11-11-2020
DOI: 10.1029/2019RG000663
Abstract: The Antarctic Ice Sheet (AIS) is out of equilibrium with the current anthropogenic‐enhanced climate forcing. Paleoenvironmental records and ice sheet models reveal that the AIS has been tightly coupled to the climate system during the past and indicate the potential for accelerated and sustained Antarctic ice mass loss into the future. Modern observations by contrast suggest that the AIS has only just started to respond to climate change in recent decades. The maximum projected sea level contribution from Antarctica to 2100 has increased significantly since the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report, although estimates continue to evolve with new observational and theoretical advances. This review brings together recent literature highlighting the progress made on the known processes and feedbacks that influence the stability of the AIS. Reducing the uncertainty in the magnitude and timing of the future sea level response to AIS change requires a multidisciplinary approach that integrates knowledge of the interactions between the ice sheet, solid Earth, atmosphere, and ocean systems and across time scales of days to millennia. We start by reviewing the processes affecting AIS mass change, from atmospheric and oceanic processes acting on short time scales (days to decades), through to ice processes acting on intermediate time scales (decades to centuries) and the response to solid Earth interactions over longer time scales (decades to millennia). We then review the evidence of AIS changes from the Pliocene to the present and consider the projections of global sea level rise and their consequences. We highlight priority research areas required to improve our understanding of the processes and feedbacks governing AIS change.
Ocean carbon and nitrogen isotopes in CSIRO Mk3L-COAL version 1.0: A tool for palaeoceanographic research
Publisher: Copernicus GmbH
Date: 27-11-2018
DOI: 10.5194/GMD-2018-225
Abstract: Abstract. The isotopes of carbon (δ13C) and nitrogen (δ15N) are commonly used proxies for understanding the ocean. When used in tandem, they provide powerful insight into physical and biogeochemical processes. Here, we detail the implementation of δ13C and δ15N in the ocean component of an Earth system model. We evaluate our simulated δ13C and δ15N against contemporary measurements, place the model's performance alongside other isotope enabled models, and document the response of δ13C and δ15N to changes in ecosystem functioning. The model combines the Commonwealth Scientific and Industrial Research Organisation Mark 3L (CSIRO Mk3L) climate system model with the Carbon of the Ocean, Atmosphere and Land (COAL) biogeochemical model. The oceanic component of CSIRO Mk3L-COAL has a resolution of 1.6° latitude × 2.8° longitude and resolves multi-millennial timescales, running at a rate of ∼400 years per day. We show that this coarse resolution, computationally efficient model adequately reproduces water column and coretop δ13C and δ15N measurements, making it a useful tool for palaeoceanographic research. Changes to ecosystem function involve varying phytoplankton stoichiometry, varying CaCO3 production based on calcite saturation state, and varying N2 fixation via iron limitation. We find that large changes in CaCO3 production have little effect on δ13C and δ15N, while changes in N2 fixation and phytoplankton stoichiometry have substantial and complex effects. Interpretations of palaeoceanographic records are therefore open to multiple lines of interpretation where multiple processes imprint on the isotopic signature, such as in the tropics where denitrification, N2 fixation and nutrient utilisation influence δ15N. Hence, there is significant scope for isotope enabled models to provide more robust interpretations of the proxy records.
Reduced oxygenation at intermediate depths of the southwest Pacific during the last glacial maximum
Publisher: Elsevier BV
Date: 06-2018
Export production in the New-Zealand region since the Last Glacial Maximum
Publisher: Elsevier BV
Date: 07-2017
Pre-concentration of thorium and neodymium isotopes using Nobias chelating resin: Method development and application to chromatographic separation
Publisher: Elsevier BV
Date: 09-2019
DOI: 10.1016/J.TALANTA.2019.03.086
Abstract: The isotopes of thorium (Th) and neodymium (Nd) are used as tracers in oceanography, and are key parameters in the international GEOTRACES program. The very low concentrations of Th and Nd as well as the reactive nature of Th isotopes makes the analysis of seawater s les a complex process. Analysis requires time-consuming pre-concentration from over 5 L of seawater. We describe a method to simultaneously pre-concentrate dissolved Th and Nd from acidified seawater s les using the Nobias
Global Ocean Sediment Composition and Burial Flux in the Deep Sea
Publisher: American Geophysical Union (AGU)
Date: 04-2021
DOI: 10.1029/2020GB006769
Abstract: Quantitative knowledge about the burial of sedimentary components at the seafloor has wide‐ranging implications in ocean science, from global climate to continental weathering. The use of 230 Th‐normalized fluxes reduces uncertainties that many prior studies faced by accounting for the effects of sediment redistribution by bottom currents and minimizing the impact of age model uncertainty. Here we employ a recently compiled global data set of 230 Th‐normalized fluxes with an updated database of seafloor surface sediment composition to derive atlases of the deep‐sea burial flux of calcium carbonate, biogenic opal, total organic carbon (TOC), nonbiogenic material, iron, mercury, and excess barium (Ba xs ). The spatial patterns of major component burial are mainly consistent with prior work, but the new quantitative estimates allow evaluations of deep‐sea budgets. Our integrated deep‐sea burial fluxes are 136 Tg C/yr CaCO 3 , 153 Tg Si/yr opal, 20Tg C/yr TOC, 220 Mg Hg/yr, and 2.6 Tg Ba xs /yr. This opal flux is roughly a factor of 2 increase over previous estimates, with important implications for the global Si cycle. Sedimentary Fe fluxes reflect a mixture of sources including lithogenic material, hydrothermal inputs and authigenic phases. The fluxes of some commonly used paleo‐productivity proxies (TOC, biogenic opal, and Ba xs ) are not well‐correlated geographically with satellite‐based productivity estimates. Our new compilation of sedimentary fluxes provides detailed regional and global information, which will help refine the understanding of sediment preservation.
Global, regional, and national levels of maternal mortality, 1990–2015: a systematic analysis for the Global Burden of Disease Study 2015
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2017
Sea ice changes in the southwest Pacific sector of the Southern Ocean during the last 140 000 years
Publisher: Copernicus GmbH
Date: 14-03-2022
Abstract: Abstract. Sea ice expansion in the Southern Ocean is believed to have contributed to glacial–interglacial atmospheric CO2 variability by inhibiting air–sea gas exchange and influencing the ocean's meridional overturning circulation. However, limited data on past sea ice coverage over the last 140 ka (a complete glacial cycle) have hindered our ability to link sea ice expansion to oceanic processes that affect atmospheric CO2 concentration. Assessments of past sea ice coverage using diatom assemblages have primarily focused on the Last Glacial Maximum (∼21 ka) to Holocene, with few quantitative reconstructions extending to the onset of glacial Termination II (∼135 ka). Here we provide new estimates of winter sea ice concentrations (WSIC) and summer sea surface temperatures (SSST) for a full glacial–interglacial cycle from the southwestern Pacific sector of the Southern Ocean using the modern analog technique (MAT) on fossil diatom assemblages from deep-sea core TAN1302-96. We examine how the timing of changes in sea ice coverage relates to ocean circulation changes and previously proposed mechanisms of early glacial CO2 drawdown. We then place SSST estimates within the context of regional SSST records to better understand how these surface temperature changes may be influencing oceanic CO2 uptake. We find that winter sea ice was absent over the core site during the early glacial period until MIS 4 (∼65 ka), suggesting that sea ice may not have been a major contributor to early glacial CO2 drawdown. Sea ice expansion throughout the glacial–interglacial cycle, however, appears to coincide with observed regional reductions in Antarctic Intermediate Water production and subduction, suggesting that sea ice may have influenced intermediate ocean circulation changes. We observe an early glacial (MIS 5d) weakening of meridional SST gradients between 42 and 59∘ S throughout the region, which may have contributed to early reductions in atmospheric CO2 concentrations through its impact on air–sea gas exchange.
Chapter 11 Sediment Signatures of U- and Th-Series Nuclides and their Application as Paleoceanographic Tracers
Publisher: Elsevier
Date: 2008
Glacial and hydrothermal sources of dissolved iron(II) in Southern Ocean waters surrounding Heard and McDonald Islands
Publisher: Wiley
Date: 27-04-2020
Input and cycling of iron in the Gulf of Aqaba, Red Sea
Publisher: American Geophysical Union (AGU)
Date: 09-2006
DOI: 10.1029/2005GB002646
A first intercomparison of the simulated LGM carbon results within PMIP-carbon: role of the ocean boundary conditions
Publisher: Wiley
Date: 11-05-2021
Scratching the Surface: A Marine Sediment Provenance Record From the Continental Slope of Central Wilkes Land, East Antarctica
Publisher: American Geophysical Union (AGU)
Date: 11-2020
DOI: 10.1029/2020GC009156
Sources of Organic Tracers in Atmospheric Dust, Surface Seawater Particulate Matter and Sediment of the Red Sea
Publisher: Springer International Publishing
Date: 07-12-2018
A comparison with natural particles reveals a small specific effect of PVC microplastics on mussel performance
Publisher: Elsevier BV
Date: 11-2020
(Table S2) Age determination of ODP Sites 202-1234 and 202-1235
Publisher: No publisher found
Date: 2010
Climate, Mixing, and Carbon Budgets in a LGM set-up of CESM
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-4837
Abstract: & & We use a free running Last Glacial Maximum (LGM) setup of CESM1 with its full ecosystem model to understand which processes are responsible for the large difference in atmospheric CO2 concentration between the LGM& and 1850 CE.& br& Just by accounting for the changed orbital forcing& and replacing today's bathymetry and icesheet orography with their Peltier et al. (2015) LGM reconstructions, leads to a 55 ppm difference in atmospheric CO2.& Additional experiments with increased aolian iron fluxes make it plausible that IPCC class ESMs can reproduce the processes that were hypothesized to be important for the observed low LGM CO2 concentration.& & & & A second focus of our study is the connection between sea level, ocean turbulence and the strengths of the various carbon pumps. Including the full amount of the suggested increase in ocean mixing during the LGM would lead to a 20 ppm larger CO2 concentration.This suggests that either mixing during the LGM is not understood yet, or that ESMs may indeed misrepresent one or more aspects of the various carbon pumps.& & & & We conclude with a discussion of uncertainties within the model setup, in particular with regards to the assumed structure of ocean mixing.& &
Ocean carbon and nitrogen isotopes in CSIRO Mk3L-COAL version 1.0: A tool for palaeoceanographic research
Publisher: Copernicus GmbH
Date: 16-04-2019
Abstract: Abstract. The isotopes of carbon (δ13C) and nitrogen (δ15N) are commonly used proxies for understanding the ocean. When used in tandem, they provide powerful insight into physical and biogeochemical processes. Here, we detail the implementation of δ13C and δ15N in the ocean component of an Earth system model. We evaluate our simulated δ13C and δ15N against contemporary measurements, place the model's performance alongside other isotope-enabled models and document the response of δ13C and δ15N to changes in ecosystem functioning. The model combines the Commonwealth Scientific and Industrial Research Organisation Mark 3L (CSIRO Mk3L) climate system model with the Carbon of the Ocean, Atmosphere and Land (COAL) biogeochemical model. The oceanic component of CSIRO Mk3L-COAL has a resolution of 1.6∘ latitude × 2.8∘ longitude and resolves multimillennial timescales, running at a rate of ∼400 years per day. We show that this coarse-resolution, computationally efficient model adequately reproduces water column and core-top δ13C and δ15N measurements, making it a useful tool for palaeoceanographic research. Changes to ecosystem function involve varying phytoplankton stoichiometry, varying CaCO3 production based on calcite saturation state and varying N2 fixation via iron limitation. We find that large changes in CaCO3 production have little effect on δ13C and δ15N, while changes in N2 fixation and phytoplankton stoichiometry have substantial and complex effects. Interpretations of palaeoceanographic records are therefore open to multiple lines of interpretation where multiple processes imprint on the isotopic signature, such as in the tropics, where denitrification, N2 fixation and nutrient utilisation influence δ15N. Hence, there is significant scope for isotope-enabled models to provide more robust interpretations of the proxy records.
Supplementary material to Sea ice and productivity changes over the last glacial cycle in the Adélie Land region, East Antarctica, based on diatom assemblage variability
Publisher: Copernicus GmbH
Date: 04-10-2022
Riverine input of macronutrients, iron, and organic matter to the coastal ocean off Oregon, U.S.A., during the winter
Publisher: Wiley
Date: 09-2006
Ice-sheet control of continental erosion in central and southern Chile (36°-41°S) over the last 30,000 years
Publisher: Elsevier BV
Date: 11-2010
The influence of particle composition and particle flux on scavenging of Th, Pa and Be in the ocean
Publisher: Elsevier BV
Date: 11-2002
Controls on biogenic silica burial in the Southern Ocean
Publisher: American Geophysical Union (AGU)
Date: 10-2015
DOI: 10.1002/2015GB005186
Discovering the ocean's past through geochemistry
Publisher: Mineralogical Society of America
Date: 12-2018
Sea ice and productivity changes over the last glacial cycle in the Adélie Land region, East Antarctica, based on diatom assemblage variability
Publisher: Copernicus GmbH
Date: 14-02-2023
Abstract: Abstract. Although diatoms can provide important palaeoenvironmental information about seasonal sea ice extent productivity, sea surface temperature, and ocean circulation variability, there are still relatively few studies analysing the last glacial cycle near the Antarctic continent. This study examines diatom assemblages over the last glacial cycle from core TAN1302-44, offshore Adélie Land, East Antarctica. Two distinct diatom assemblages were identified using principal component analysis (PC 1–PC 2). The PC 1 assemblage is characterised by Thalassiosira lentiginosa, Actinocyclus actinochilus, Euc ia antarctica, Azpeitia tabularis and Asteromphalus hyalinus and is associated with the interglacial, sedimentary Facies 1, suggesting that the MIS 5e and Holocene interglacials were characterised by seasonal sea ice environments with similar ocean temperature and circulation. The PC 2 assemblage is characterised by Fragilariopsis obliquecostata, Asteromphalus parvulus and Thalassiosira tumida and is associated with the glacial Facies 2. The variability of PC 2 indicates that, during the MIS 4–2 glacial and the last glaciation, there was an increase in the length of the sea ice season compared with that of the interglacial period, yet there was still no permanent sea ice cover. The initial increase of PC 2 at the start of the glaciation stage and then the gradual increase throughout late MIS 4–2 suggest that sea ice cover steadily increased, reaching a maximum towards the end of MIS 2. The increase in sea ice during glaciation and MIS 4–2 glacial is further supported by the increase in the Euc ia index (terminal/intercalary valve ratio), an additional proxy for sea ice, which coincides with increases in PC 2. Aside from the statistical results, the increase in the relative abundance of Thalassiothrix antarctica at 40 and 270 cm suggests that, during the last two deglacials, there was a period of enhanced nutrient delivery, which is inferred to reflect an increase in upwelling of Circumpolar Deep Water. Interestingly, the diatom data suggest that, during the last deglacial, the onset of increased Circumpolar Deep Water occurred after the loss of a prolonged sea ice season (decrease in PC 2) but before the ice sheet started to retreat (increase in IRD). Together, these results suggest the changes in sea ice season potentially influenced the ocean's thermohaline circulation and were important factors in driving the climate transitions. The results contribute to our understanding of the sea ice extent and ocean circulation changes proximal to East Antarctica over the last glacial cycle.
Lithogenic inputs to the Southern Ocean assessed with thorium and rare earth elements
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-12068
Abstract: & & & & & & & The Southern Ocean is a key regulator of global climate, and it& #8217 s responsible for about one-quarter of the global carbon export. Part of this export is fuelled by phytoplankton, however, in some areas of the ocean, phytoplankton activity remains to a minimum despite the abundance of nutrients. These areas, known as high nutrient low chlorophyll (HNLC), from which the Southern Ocean is the largest one, exist due to the absence of the micro-nutrient iron (Fe). The Kerguelen Plateau located in the Indian sector of the SO hosts one of the largest phytoplankton blooms in the SO during spring and summer. This study focused on the role of Heard and McDonald Islands, located in the southern part of the Kerguelen Plateau, on the Fe fertilization of the whole region, and their role in overcoming HNLC conditions. For this, we combined thorium, rare earth element concentrations and Nd isotopic composition to trace the lithogenic supply of Fe. Our results highlight the importance of Heard and Mc Donald Islands, surrounding shallow areas and probably the melting of glaciers from Heard Island on the supply of Fe that fuels the bloom in the region.& We used thorium isotopes (& sup& & /sup& Th and & sup& & /sup& Th) to estimate the flux of Fe produced by the dissolution of lithogenic particles. These results suggest that thorium isotopes can be used to calculate the fluxes of other elements not only in the remote open ocean but also near continental margins. Cerium and europium anomalies, together with the neodymium isotopic composition data seem to indicate that Heard and McDonald Islands are the main contributors to the natural Fe fertilization of the region. This study highlights the need for more systematic studies to obtain a better understanding of the functioning of the Southern Ocean carbon pump and its relationship with global climate.& &
Southern Ocean Iron Enrichment Experiment: Carbon Cycling in High- and Low-Si Waters
Publisher: American Association for the Advancement of Science (AAAS)
Date: 16-04-2004
Abstract: The availability of iron is known to exert a controlling influence on biological productivity in surface waters over large areas of the ocean and may have been an important factor in the variation of the concentration of atmospheric carbon dioxide over glacial cycles. The effect of iron in the Southern Ocean is particularly important because of its large area and abundant nitrate, yet iron-enhanced growth of phytoplankton may be differentially expressed between waters with high silicic acid in the south and low silicic acid in the north, where diatom growth may be limited by both silicic acid and iron. Two mesoscale experiments, designed to investigate the effects of iron enrichment in regions with high and low concentrations of silicic acid, were performed in the Southern Ocean. These experiments demonstrate iron's pivotal role in controlling carbon uptake and regulating atmospheric partial pressure of carbon dioxide.
Developing standards for dissolved iron in seawater
Publisher: American Geophysical Union (AGU)
Date: 13-03-2007
DOI: 10.1029/2007EO110003
Comment on Do geochemical estimates of sediment focusing pass the sediment test in the equatorial Pacific? by M. Lyle et al
Publisher: American Geophysical Union (AGU)
Date: 03-2007
DOI: 10.1029/2005PA001235
High lability Fe particles sourced from glacial erosion can meet previously unaccounted biological demand: Heard Island, Southern Ocean
Publisher: Frontiers Media SA
Date: 14-06-2019
Controls on deglacial changes in biogenic fluxes in the North Pacific Ocean
Publisher: Elsevier BV
Date: 11-2011
Improved methodology for the microwave digestion of carbonate-rich environmental samples
Publisher: Informa UK Limited
Date: 25-01-2016
Quantifying and characterising metal concentrations in Derwent Estuary sediments using portable X-ray fluorescence spectrometry
Publisher: Informa UK Limited
Date: 20-02-2022
Evaluating the impact of atmospheric deposition on dissolved trace-metals in the Gulf of Aqaba, Red Sea
Publisher: Elsevier BV
Date: 09-2011
Radiocarbon, isotope, biogenic, and 230Th measurements for sediment core RC10-196
Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
Date: 2011
Investigating the effect of silicate and calcium based ocean alkalinity enhancement on diatom silicification
Publisher: Copernicus GmbH
Date: 12-09-2023
DOI: 10.5194/BG-2023-144
Iron links river runoff and shelf width to phytoplankton biomass along the U.S. West Coast
Publisher: American Geophysical Union (AGU)
Date: 02-2007
DOI: 10.1029/2006GL028069
Benthic remineralization and burial of biogenic SiO2 , CaCO3 , organic carbon, and detrital material in the Southern Ocean along a transect at 170° West
Publisher: Elsevier BV
Date: 2001
Metabolic consequences of iron deficiency in heterotrophic marine protozoa
Publisher: Wiley
Date: 12-1997
Scavenging of 230Th, 231Pa and 10Be in the Southern Ocean (SW Pacific sector): The importance of particle flux, particle composition and advection
Publisher: Elsevier BV
Date: 03-2003
The simulated climate of the Last Glacial Maximum and insights into the global marine carbon cycle
Publisher: Copernicus GmbH
Date: 17-03-2009
Abstract: Abstract. The ocean's ability to store large quantities of carbon, combined with the millennial longevity over which this reservoir is overturned, has implicated the ocean as a key driver of glacial–interglacial climates. However, the combination of processes that cause an accumulation of carbon within the ocean during glacial periods is still under debate. Here we present simulations of the Last Glacial Maximum (LGM) using the CSIRO Mk3L-COAL (Carbon–Ocean–Atmosphere–Land) earth system model to test the contribution of physical and biogeochemical processes to ocean carbon storage. For the LGM simulation, we find a significant global cooling of the surface ocean (3.2 °C) and the expansion of both minimum and maximum sea ice cover broadly consistent with proxy reconstructions. The glacial ocean stores an additional 267 Pg C in the deep ocean relative to the pre-industrial (PI) simulation due to stronger Antarctic Bottom Water formation. However, 889 Pg C is lost from the upper ocean via equilibration with a lower atmospheric CO2 concentration and a global decrease in export production, causing a net loss of carbon relative to the PI ocean. The LGM deep ocean also experiences an oxygenation ( 100 mmol O2 m−3) and deepening of the calcite saturation horizon (exceeds the ocean bottom) at odds with proxy reconstructions. With modifications to key biogeochemical processes, which include an increased export of organic matter due to a simulated release from iron limitation, a deepening of remineralisation and decreased inorganic carbon export driven by cooler temperatures, we find that the carbon content of the glacial ocean can be sufficiently increased (317 Pg C) to explain the reduction in atmospheric and terrestrial carbon at the LGM (194 ± 2 and 330 ± 400 Pg C, respectively). Assuming an LGM–PI difference of 95 ppm pCO2, we find that 55 ppm can be attributed to the biological pump, 28 ppm to circulation changes and the remaining 12 ppm to solubility. The biogeochemical modifications also improve model–proxy agreement in export production, carbonate chemistry and dissolved oxygen fields. Thus, we find strong evidence that variations in the oceanic biological pump exert a primary control on the climate.
Microplastic Pollution in Deep-Sea Sediments From the Great Australian Bight
Publisher: Frontiers Media SA
Date: 05-10-2020
Benthic fluxes on the Oregon shelf
Publisher: Elsevier BV
Date: 09-2015
Comment on On the importance of opal, carbonate, and lithogenic clays in scavenging and fractionating 230Th, 231Pa and 10Be in the ocean by S. Luo and T.-L. Ku
Publisher: Elsevier BV
Date: 03-2004
Accumulation of biogenic and lithogenic material in the Pacific sector of the Southern Ocean during the past 40,000 years
Publisher: Elsevier BV
Date: 03-2003
Different mechanisms of silicic acid leakage and their biogeochemical consequences
Publisher: American Geophysical Union (AGU)
Date: 03-2014
DOI: 10.1002/2013PA002588
Sources and fluxes of atmospheric trace elements to the Gulf of Aqaba, Red Sea
Publisher: American Geophysical Union (AGU)
Date: 06-03-2008
DOI: 10.1029/2007JD009110
14 Southern Ocean Sea Surface Temperature records recalibrated to MARINE20 and tied to the AICC2012 Timescale, Southern Ocean Sea Surface Temperature Anomaly Stacks
Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
Date: 2020
Climatically driven changes in oceanic processes throughout the equatorial Pacific
Publisher: American Geophysical Union (AGU)
Date: 18-11-2004
DOI: 10.1029/2004PA001024
Total Uranium, Rhenium and Thorium concentrations since the last glacial maximum from 13 sediment cores from the southwest Pacific sector of the Southern Ocean
Publisher: No publisher found
Date: 2016
Dynamic Biological Functioning Important for Simulating and Stabilizing Ocean Biogeochemistry
Publisher: American Geophysical Union (AGU)
Date: 04-2018
DOI: 10.1002/2017GB005753
Abstract: The biogeochemistry of the ocean exerts a strong influence on the climate by modulating atmospheric greenhouse gases. In turn, ocean biogeochemistry depends on numerous physical and biological processes that change over space and time. Accurately simulating these processes is fundamental for accurately simulating the ocean's role within the climate. However, our simulation of these processes is often simplistic, despite a growing understanding of underlying biological dynamics. Here we explore how new parameterizations of biological processes affect simulated biogeochemical properties in a global ocean model. We combine 6 different physical realizations with 6 different biogeochemical parameterizations (36 unique ocean states). The biogeochemical parameterizations, all previously published, aim to more accurately represent the response of ocean biology to changing physical conditions. We make three major findings. First, oxygen, carbon, alkalinity, and phosphate fields are more sensitive to changes in the ocean's physical state. Only nitrate is more sensitive to changes in biological processes, and we suggest that assessment protocols for ocean biogeochemical models formally include the marine nitrogen cycle to assess their performance. Second, we show that dynamic variations in the production, remineralization, and stoichiometry of organic matter in response to changing environmental conditions benefit the simulation of ocean biogeochemistry. Third, dynamic biological functioning reduces the sensitivity of biogeochemical properties to physical change. Carbon and nitrogen inventories were 50% and 20% less sensitive to physical changes, respectively, in simulations that incorporated dynamic biological functioning. These results highlight the importance of a dynamic biology for ocean properties and climate.
The simulated climate of the Last Glacial Maximum and insights into the global carbon cycle
Publisher: Copernicus GmbH
Date: 11-07-2016
DOI: 10.5194/CP-2016-73
Abstract: Abstract. The ocean's ability to store large quantities of carbon, combined with the millennial longevity over which this reservoir is overturned, has implicated the ocean as a key driver of glacial-interglacial climates. However, the combination of processes that cause an accumulation of carbon within the ocean during glacial periods is still under debate. Here we present simulations of the Last Glacial Maximum (LGM) using the CSIRO Mk3L-COAL Earth System Model to test the contribution of physical and biogeochemical processes to ocean carbon storage. For the LGM simulation, we find a significant global cooling of the surface ocean (3.2 °C) and the expansion of both minimum (Northern Hemisphere: 105 % Southern Hemisphere: 225 %) and maximum (Northern Hemisphere: 145 % Southern Hemisphere: 120 %) sea ice cover broadly consistent with proxy reconstructions. Within the ocean, a significant reorganisation of the large-scale circulation and biogeochemical fields occurs. The LGM simulation stores an additional 322 Pg C in the deep ocean relative to the Pre-Industrial (PI) simulation, particularly due to a strengthening in Antarctic Bottom Water circulation. However, 839 Pg C is lost from the upper ocean via equilibration with a lower atmospheric CO2 concentration, causing a net loss of 517 Pg C relative to the PI simulation. The LGM deep ocean also experiences an oxygenation ( 100 mmol O2 m−3) and deepening of the aragonite saturation depth ( 2000 m deeper) at odds with proxy reconstructions. Hence, physical changes cannot in isolation produce plausible biogeochemistry nor the required drawdown of atmospheric CO2 of 80–100 ppm at the LGM. With modifications to key biogeochemical processes, which include an increased export of organic matter due to a simulated release from iron limitation, a deepening of remineralisation and decreased inorganic carbon export driven by cooler temperatures, we find that the carbon content in the glacial oceanic reservoir can be increased (326 Pg C) to a level that is sufficient to explain the reduction in atmospheric and terrestrial carbon at the LGM (520 ± 00 Pg C). These modifications also go some way to reconcile simulated export production, aragonite saturation state and oxygen fields with those that have been reconstructed by proxy measurements, thereby implicating changes in ocean biogeochemistry as an essential driver of the climate system.
Manganese and iron distributions off central California influenced by upwelling and shelf width
Publisher: Elsevier BV
Date: 06-2005
Scratching the surface: a new marine sediment provenance record from the continental slope of central Wilkes Land, East Antarctica, supplement to: Tooze, Sian; Halpin, Jacqueline; Chase, Zanna; Armand, Leanne K; O'Brian, Philip; Noble, Taryn L (in prep.): Scratching the surface: a new marine sediment provenance record from the continental slope of central Wilkes Land, East Antarctica. Geochemistry, Geophysics, Geosystems
Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
Date: 2019
Erratum: Iron links river runoff and shelf width to phytoplankton biomass along the U.S. West Coast (Geophysical Research Letters (2007) vol. 34 10.1029/2006GL028069)
Publisher: American Geophysical Union (AGU)
Date: 04-2007
DOI: 10.1029/2007GL029924
A First Intercomparison of the Simulated LGM Carbon Results Within PMIP‐Carbon: Role of the Ocean Boundary Conditions
Publisher: American Geophysical Union (AGU)
Date: 29-09-2021
DOI: 10.1029/2021PA004302
Abstract: Model intercomparison studies of coupled carbon‐climate simulations have the potential to improve our understanding of the processes explaining the drawdown at the Last Glacial Maximum (LGM) and to identify related model biases. Models participating in the Paleoclimate Modeling Intercomparison Project (PMIP) now frequently include the carbon cycle. The ongoing PMIP‐carbon project provides the first opportunity to conduct multimodel comparisons of simulated carbon content for the LGM time window. However, such a study remains challenging due to differing implementation of ocean boundary conditions (e.g., bathymetry and coastlines reflecting the low sea level) and to various associated adjustments of biogeochemical variables (i.e., alkalinity, nutrients, dissolved inorganic carbon). After assessing the ocean volume of PMIP models at the pre‐industrial and LGM, we investigate the impact of these modeling choices on the simulated carbon at the global scale, using both PMIP‐carbon model outputs and sensitivity tests with the iLOVECLIM model. We show that the carbon distribution in reservoirs is significantly affected by the choice of ocean boundary conditions in iLOVECLIM. In particular, our simulations demonstrate a GtC effect of an alkalinity adjustment on carbon sequestration in the ocean. Finally, we observe that PMIP‐carbon models with a freely evolving and no additional glacial mechanisms do not simulate the drawdown at the LGM (with concentrations as high as 313, 331, and 315 ppm), especially if they use a low ocean volume. Our findings suggest that great care should be taken on accounting for large bathymetry changes in models including the carbon cycle.
The impact of bathymetry on the simulated carbon at the Last Glacial Maximum
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-7297
Abstract: & & Understanding the processes causing variations in the carbon cycle is critical to accurately simulate the future carbon cycle and climate. Paleoclimate models can provide insights about these processes since they are used under different conditions than present-day& #8217 s and evaluated against paleoproxy data. In particular, the Last Glacial Maximum (LGM) has been a focus of the Paleoclimate Modelling Intercomparison Project (PMIP) as it is well-documented thanks to numerous paleoclimate archives. Around 21,000 years ago, the LGM was a colder period with extensive ice sheets in the Northern Hemisphere and a resulting lower sea-level. Although this period has been studied for years, the causes of the lower atmospheric CO& sub& & /sub& concentration at the time (around 186 ppm, against 280 ppm at the pre-industrial) remain unclear, and models struggle to simulate this low CO& sub& & /sub& value. The ocean is thought to have played a significant role due to different processes (through changes of the biological pump efficiency, ocean circulation, sea-ice, and CO& sub& & /sub& solubility due to colder temperatures), but no consensus has been reached yet as to their contribution (Khatiwala et al. [2019], Yu et al. [2016], Marzocchi and Jansen [2019]).& & & & Despite the carbon cycle being simulated by more and more climate models, it has not been systematically analysed within the framework of PMIP multimodel comparisons. In this context, the ongoing PMIP-carbon project aims at comparing climate-carbon interactions in LGM simulations, and includes results from both intermediate complexity models and general circulation models. The PMIP protocol proposes standardized forcing parameters and boundary conditions (Kageyama et al. [2017]) and specifies a few recommendations for ocean biogeochemistry models (adjustment of salinity, dissolved inorganic carbon, alkalinity, and nutrients to account for the change in ocean volume). Indeed, the bathymetric changes associated with a sea-level drop of 133 m entail a change of the reservoir size and potential technical issues concerning the conservation of carbon.& & & & In this study, we use outputs from PMIP-carbon models and other models available on the ESGF (MIROC4m-COCO, MIROC-ES2L, CESM, IPSL-CM5A2, UVic, LOVECLIM, iLOVECLIM, CLIMBER_2P GISS-E2-R, MRI-CGCM3, MPI-ESM-P, CNRM-CM5, MIROC-ESM) to compute total ocean volumes and compare them to high resolution topographic data (etopo1 for the PI, GLAC-1D and ICE-6G-C for the LGM). We show that the deglacial volume change is rarely accurate. We then use the iLOVECLIM model with a new bathymetry implementation method (Lhardy et al. [in review, 2020]) to demonstrate the effect of an improved ocean volume on the simulated oceanic carbon content, resulting in an increase of the already overestimated atmospheric CO& sub& & /sub& concentration. We also quantify the effect of the mentioned adjustments of salinity, alkalinity, and carbon. The results reinforce the idea that a realistic ocean volume is needed, as well as consistency between models in dealing with large changes in bathymetry.& &
Dust and pyrogenic iron boost phytoplankton blooms in sub-Antarctic waters of the Tasman Sea
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-7809
Abstract: & & Although it is commonly accepted that atmospheric deposition of Fe particles can fertilise phytoplankton, there is yet no clear evidence on how such a fertilisation effect takes place. Several studies have attempted to link in idual dust events with surface chlorophyll responses but generally, they do not find a clear correspondence between dust deposition and its impact on chlorophyll. In this work, we use a biogeochemical model to show that the atmospheric deposition of Fe in high-latitude seas, rather than creating instantaneous phytoplankton responses, replenish the upper mixed layer of the ocean during the pre-bloom period, from winter to early summer. The Fe accumulated at the surface boosts the phytoplankton bloom of the following summer, resulting in surface chlorophyll accumulations of up to 3 times larger than the years without atmospheric deposition. We used this mechanism to explain the strong inter-annual variability of the phytoplankton bloom in sub-Antarctic iron-limited waters east of Australia. Putting together more than a 15-years-long record of ocean colour observations and atmospheric aerosols reanalysis we uncovered a strong correlation (r& sup& & /sup& & .6) between the dust that crossed the region during the pre-bloom period and the magnitude of the surface chlorophyll bloom. Interestingly, the correlation increased when taking into account pyrogenic aerosols in addition to dust. Our study presents the first observational link between Climate Change-enhanced droughts and wildfires, atmospheric aerosols and primary production of iron-limited waters.& &
Acid mine tailings in southern Spain
Publisher: Elsevier BV
Date: 12-1999
Dissolution of fluoride complexes following microwave-assisted hydrofluoric acid digestion of marine sediments
Publisher: Elsevier BV
Date: 2012
DOI: 10.1016/J.TALANTA.2011.11.081
Abstract: Microwave-assisted, hydrofluoric acid digestion is an increasingly common tool for the preparation of marine sediment s les for analysis by a variety of spectrometric techniques. Here we report that analysis of terrigenous-dominated sediment s les occasionally results in anomalously low values for several elements, including Al, Ba, Ca, Mg, and Sr. Measured concentrations of these elements increased with time between s le preparation and s le analysis, reaching stable values after 8-29 days. This lag is explained by the formation and subsequent dissolution of poorly soluble fluoride phases during digestion. Other elements, such as Fe, Mn, and Ti, showed little or no lag and were quickly measurable at a stable value. Full re-dissolution of the least soluble fluorides, which incorporate Al and Mg, requires up to four weeks at room temperature, and this duration can vary among sedimentary matrices. This waiting time can be reduced to 6 days (or shorter) if the s les are heated to ≈ 60°C for 24h.
Health effects of dietary risks in 195 countries, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017
Publisher: Elsevier BV
Date: 05-2019
Southern Ocean Phytoplankton Stimulated by Wildfire Emissions and Sustained by Iron Recycling
Publisher: American Geophysical Union (AGU)
Date: 03-06-2202
DOI: 10.1029/2021GL097538
Abstract: Large ash plumes emitted by the 2019–2020 Australian wildfires were associated with a widespread phytoplankton bloom in the iron‐limited Pacific sector of the Southern Ocean. In this study, we used satellite observations and aerosol reanalysis products to study the regional phytoplankton community response to wildfire emissions. The bloom was stimulated by pyrogenic iron fertilization and coincided with elevated cellular pigment concentrations, increased photochemical efficiency, and apparent community structural shifts. Physiological anomalies were consistent with previously observed phytoplankton responses to iron stress relief and persisted for up to 9 months. Supported by a regional iron budget, we conclude that the bloom was sustained by iron recycling and episodic inputs of pyrogenic and dust‐borne mineral iron. The continuous regeneration of iron was likely facilitated by the bloom's large size, mitigating edge dilution effects, as well as enhanced bioavailability of pyrogenic and mineral iron due to atmospheric and chemical processing during long‐range transport.
The Southern Ocean's biological pump during the Last Glacial Maximum
Publisher: Elsevier BV
Date: 2002
Reactive iron and manganese distributions in seabed sediments near small mountainous rivers off Oregon and California (USA)
Publisher: Elsevier BV
Date: 02-2013
Effect of iron limitation on the cadmium to phosphorus ratio of natural phytoplankton assemblages from the Southern Ocean
Publisher: Wiley
Date: 05-2003
Observing biogeochemical cycles at global scales with profiling floats and gliders: Prospects for a global array
Publisher: The Oceanography Society
Date: 09-2009
A review of the Australian-New Zealand sector of the Southern Ocean over the last 30ka (Aus-INTIMATE project)
Publisher: Elsevier BV
Date: 08-2013
Sea ice and productivity changes over the last glacial cycle in the Adélie Land region, East Antarctica, based on diatom assemblage variability
Publisher: Copernicus GmbH
Date: 04-10-2022
DOI: 10.5194/EGUSPHERE-2022-1009
Abstract: Abstract. Diatoms can provide important paleoenvironmental information about seasonal sea ice extent, productivity, sea surface temperature and ocean circulation variability, yet there are relatively few studies analysing the last glacial cycle near the Antarctic continent. This study examines diatom assemblages over the last glacial cycle from core TAN1302-44, from off Adélie Land, East Antarctica. Four distinct diatom assemblages were identified using principal components analyses. The PC 1 assemblage is associated with the interglacial, sedimentary facies, Facies 1, and comprises Thalassiosira lentiginosa, Actinocyclus actinochilus, Euc ia antarctica, Azpeitia tabularis and Asteromphalus hyalinus, suggesting that MIS 5e and Holocene interglacial time periods were characterised by seasonal sea ice environments with similar ocean temperature and circulation. The PC 2 assemblage is associated with the glacial, Facies 2, and comprises Fragilariopsis obliquecostata, Asteromphalus parvulus, Rhizosolenia styliformis, Thalassiosira tumida, Chaetoceros dichaeta, and a Euc ia antarctica terminal/intercalary ratio. This indicates that, during the MIS 4-2 glacial there was an increase in the length of the sea ice season compared with the interglacial period, yet still no permanent sea ice cover. The PC 2 assemblage is also associated with the glaciation and deglacial facies. There is an initial increase of PC 2 at the start of MIS 5d-a glaciation stage and then a gradual increase throughout late MIS 4-2, suggests that sea ice cover steadily increased reaching a maximum at the end of MIS 2. The PC 3 assemblage is associated with all four facies and comprises Actinocyclus ingens, Actinocyclus actinochilus, Thalassiosira oliverana and Fragilariopsis kerguelensis, suggesting that reworking of sediments and an influx of older sediments occurred throughout the last glacial cycle. Finally, the PC 4 assemblage is associated with the deglacial, glaciation, and glacial facies and comprises Fragilariopsis kerguelensis, Thalassiothrix antarctica, Chaetoceros bulbosum and Euc ia antarctica, suggesting that during the last glaciation, the last two deglacials, and the early glacial, there was a period of enhanced upwelling of nutrient-rich, warmer water, which is inferred to reflect an increase in Circumpolar Deep Water. Interestingly, the diatom data suggest the onset of increased Circumpolar Deep Water during the last deglacial occurred after the rapid loss of a prolonged sea ice season at the end of last glacial. Together, these results suggest changes in ocean circulation and sea ice season were important factors during climate transitions. The results fill a gap in our understanding of the sea ice extent and ocean circulation changes proximal to East Antarctica over the last glacial cycle.
Chemical pollutants in the marine environment: causes, effects, and challenges
Publisher: Oxford University Press
Date: 03-2016
Biogeochemical characteristics of eddies in the East Australian Current depend on eddy type, history and location
Publisher: Elsevier BV
Date: 04-2021
Glacial and Hydrothermal Sources of Dissolved Iron (II) in Southern Ocean Waters Surrounding Heard and McDonald Islands
Publisher: American Geophysical Union (AGU)
Date: 25-09-2020
DOI: 10.1029/2020JC016286
Global Ocean Sediment Composition and Burial Flux in the Deep Sea
Publisher: American Geophysical Union
Date: 2021
DOI: 10.48350/156239
Th-normalized fluxes, mass accumulation rates and age models of ODP Sites 202-1233 and 202-1234, supplement to: Chase, Zanna; McManus, James; Mix, Alan C; Muratli, Jesse M (2014): Southern-ocean and glaciogenic nutrients control diatom export production on the Chile margin. Quaternary Science Reviews, 99, 135-145
Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
Date: 2014
Vertical budgets for organic carbon and biogenic silica in the Pacific sector of the Southern Ocean, 1996-1998
Publisher: Elsevier BV
Date: 2002
Geochemistry of ODP Site 202-1233 and river sediments
Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
Date: 2010
Iron availability influences nutrient drawdown in the Heard and McDonald Islands region, Southern Ocean
Publisher: Elsevier BV
Date: 04-2019
Quantifying Lithogenic Inputs to the Southern Ocean Using Long-Lived Thorium Isotopes
Publisher: Frontiers Media SA
Date: 22-04-2020
Development and initial deployments of an autonomous in situ instrument for long-term monitoring of copper (II) in the marine environment
Publisher: Wiley
Date: 07-2008
Appreciating GBC 2022 Reviewers
Publisher: American Geophysical Union (AGU)
Date: 08-2023
DOI: 10.1029/2023GB007867
Abstract: The Editors of the Global Biogeochemical Cycles express their appreciation to those who served as peer reviewers for the journal in 2022.
Microplate-reader method for the rapid analysis of copper in natural waters with chemiluminescence detection
Publisher: Frontiers Media SA
Date: 2012
Temporal evolution of mechanisms controlling ocean carbon uptake during the last glacial cycle
Publisher: Elsevier BV
Date: 08-2017
Southern-ocean and glaciogenic nutrients control diatom export production on the Chile margin
Publisher: Elsevier BV
Date: 09-2014
Tracking Southern Ocean Sea Ice Extent With Winter Water: A New Method Based on the Oxygen Isotopic Signature of Foraminifera
Publisher: American Geophysical Union (AGU)
Date: 31-05-2021
DOI: 10.1029/2020PA004095
Abstract: Southern Ocean sea ice plays a central role in the oceanic meridional overturning circulation, transforming globally prevalent watermasses through surface buoyancy loss and gain. Buoyancy loss due to surface cooling and sea ice growth promotes the formation of bottom water that flows into the Atlantic, Indian, and Pacific basins, while buoyancy gain due to sea ice melt helps transform the returning deep flow into intermediate and mode waters. Because northward expansion of Southern Ocean sea ice during the Last Glacial Maximum (LGM 19–23 kyr BP) may have enhanced deep ocean stratification and contributed to lower atmospheric CO 2 levels, reconstructions of sea ice extent are critical to understanding the LGM climate state. Here, we present a new sea ice proxy based on the 18 O/ 16 O ratio of foraminifera (δ 18 O c ). In the seasonal sea ice zone, sea ice formation during austral winter creates a cold surface mixed layer that persists in the sub‐surface during spring and summer. The cold sub‐surface layer, known as winter water, sits above relatively warm deep water, creating an inverted temperature profile. The unique surface‐to‐deep temperature contrast is reflected in estimates of equilibrium δ 18 O c , implying that paired analysis of planktonic and benthic foraminifera can be used to infer sea ice extent. To demonstrate the feasibility of the δ 18 O c method, we present a compilation of N. pachyderma and Cibicidoides spp. results from the Atlantic sector that yields an estimate of winter sea ice extent consistent with modern observations.
Carbon cycle response to Dansgaard-Oeschger events in a freely oscillating LGM setup of the Community Earth System Model.
Publisher: Copernicus GmbH
Date: 03-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-1556
Abstract: & & We use a LGM setup of the CESM with marine and terrestrial biogeochemistry. This free-running& set-up (i.e., no freshwater hosing) exhibts Dansgaard-Oeschger events and Antarctic Isotope Maxima with time-lags and litudes that are consistent with paleo reconstructions. The CO2 signal associated DO events is also consistent with reconstructions: a 10 ppm/kyr increase during stadials, with the increase continuing some 400 years after Antarctica has started to cool again. An analysis of the modelled air-sea/land carbon fluxes reveals that some 3ppm of the stadial increase are due to shifting rain and temperature patterns that reduce growth of land vegetation. This adjustment is largely concluded after 3 centuries. The remainder of the signal is due to reduced ocean uptake. It turns out that reduced subduction of carbon in the Southern Ocean is mostly compensated by reduced upwelling in the equatorial oceans. Thus, as found in previous studies, much of the extra carbon is due to reduced uptake in the North Atlantic, partly directly due to reduced deep convection, and partly due to a reduced biological productivity because much of the North Atlantic nutrients are supplied by the AMOC. A big surprise is the emergence of the North Pacific as a major contributor to the changes in the air-fluxes of carbon. It is the reorganization of its wind-driven circulation that explains why global net-outgassing of carbon continues long after the interstadial has begun.& &
Sea Ice Changes in the Southwest Pacific Sector of the Southern Ocean During the Last 140,000 Years
Publisher: Copernicus GmbH
Date: 17-08-2021
DOI: 10.5194/CP-2021-107
Abstract: Abstract. Sea ice expansion in the Southern Ocean is believed to have contributed to glacial-interglacial atmospheric CO2 variability by inhibiting air-sea gas exchange and influencing the ocean’s meridional overturning circulation. However, limited data on past sea ice coverage over the last 140 ka (a complete glacial cycle) have hindered our ability to link sea ice expansion to oceanic processes that affect atmospheric CO2 concentration. Assessments of past sea ice coverage using diatom assemblages have primarily focused on the Last Glacial Maximum (~21 ka) to Holocene, with few quantitative reconstructions extending to the onset of glacial Termination II (~135 ka). Here we provide new estimates of winter sea ice concentrations (wSIC) and summer sea surface temperatures (sSSTs) for a full glacial-interglacial cycle from the southwestern Pacific sector of the Southern Ocean using fossil diatom assemblages from deep-sea core TAN1302-96 (59.09° S, 157.05° E, water depth 3099 m). We find that winter sea ice was consolidated over the core site during the latter part of the penultimate glaciation, Marine Isotope Stage (MIS) 6 (from at least 140 to 134 ka), when sSSTs were between ~1 and 1.5 °C. The winter sea ice edge then retreated rapidly as sSSTs increased during the transition into the Last Interglacial Period (MIS 5e), reaching ~4.5 °C by 125 ka. As the Earth entered the early glacial stages, sSSTs began to decline around 112 ka, but winter sea ice largely remained absent until ~65 ka during MIS 4, when it was sporadically present but unconsolidated ( 40 % wSIC). WSIC and sSSTs reached their maximum concentration and coolest values by 24.5 ka, just prior to the Last Glacial Maximum. Winter sea ice remained absent throughout the Holocene, while SSSTs briefly exceeded modern values, reaching ~5 °C by 11.4 ka, before decreasing to ~4 °C and stabilizing. The absence of sea ice coverage over the core site during the early glacial period suggests that sea ice may not have been a major contributor to CO2 drawdown at this time. During MIS 5d, we observe a weakening of meridional SST gradients between 42° to 59° S throughout the region, which may have contributed to early reductions in atmospheric CO2 concentrations through its impact on air-sea gas exchange. Sea ice expansion during MIS 4, however, coincides with observed reductions in Antarctic Intermediate Water production and subduction, suggesting that sea ice may have influenced intermediate ocean circulation changes.
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