ORCID Profile
0000-0003-1901-0367
Current Organisations
University of Cambridge
,
British Antarctic Survey
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Publisher: Elsevier BV
Date: 03-2016
Publisher: American Geophysical Union (AGU)
Date: 07-06-2019
DOI: 10.1029/2019GL082971
Publisher: Proceedings of the National Academy of Sciences
Date: 14-03-2016
Abstract: Antarctic ice cores provide a precise, well-dated history of increasing atmospheric CO 2 during the last glacial to interglacial transition. However, the mechanisms that drive the increase remain unclear. Here we reconstruct a key indicator of the sources of atmospheric CO 2 by measuring the stable isotopic composition of CO 2 in s les spanning the period from 22,000 to 11,000 years ago from Taylor Glacier, Antarctica. Improvements in precision and resolution allow us to fingerprint CO 2 sources on the centennial scale. The data reveal two intervals of rapid CO 2 rise that are plausibly driven by sources from land carbon (at 16.3 and 12.9 ka) and two others that appear fundamentally different and likely reflect a combination of sources (at 14.6 and 11.5 ka).
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-9210
Abstract: & & Some modelling studies and sea level reconstructions suggest the loss of the West Antarctic Ice Sheet (WAIS) during the Last Interglacial (LIG) about ~120& #8217 ago, but direct evidence for a collapse of the WAIS is lacking. The WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial (WACSWAIN) project aims at providing direct evidence allowing for a comprehensive assessment of whether or not the WAIS collapsed during the LIG. One of the expected consequences of such massive ice mass loss is the change of the elevation of land masses in close proximity of the WAIS due to isostatic adjustments. This process, together with changes in ice sheet thickness, may have altered the elevation of Skytrain Ice Rise above sea level on the order of 200 m. Such major changes in the elevation should be imprinted in the Total Air Content (TAC) based on simple barometric considerations. Here we present a new experimental setup of a high-accuracy, high-precision TAC measurement system constructed at the British Antarctic Survey. This setup is dedicated to and optimised for the measurement of TAC and is based on a vacuum extraction principle. The air is extracted from the ice by melting the s le by thermal radiation and the released air is dried and directly expanded into a 30-litre expansion chamber. State-of-the-art pressure gauges and thorough temperature control allow for an accuracy of 0.2% with a real ice reproducibility of 0.2% to 0.4% for 100 g and 30 g s les, respectively. Here, we discuss the performance of this new TAC system and present first TAC data from the Holocene section of the Skytrain Ice Core, Antarctica.& &
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-2075
Abstract: & & We present new measurements of methane (CH4) and carbon dioxide (CO2) in the Skytrain ice core, with gas ages dated around 1610AD. The aim of these measurements is to improve our understanding of why there is a significant difference between measured CO2 at that time in current ice core records.& & & & A pronounced feature of the Law Dome record (accumulation 60 cm ice eq. yr gas age distribution 8 years,) is a rapid decrease in CO2 of ~10 ppm over 50 years with a distinct minimum at 1610. The cause of this decrease is much debated, with complex carbon cycle feedbacks required in explanation. However, other ice cores do not show the same event. The West Antarctic Ice Sheet (WAIS) ide record (accumulation 22 cm ice eq. yr gas age distribution 19 years) shows a steadier decline in CO2 of approximately 6 ppm over the same period, with the record also ~2-3 ppm higher than Law Dome throughout 900-1800 CE. A follow-up study using the Dronning Maud Land (DML) ice core (accumulation 7 cm ice eq. yr gas age distribution 65 years) attempted to prove which core showed the real atmospheric signal, but results were inconclusive due to the wide gas-age distribution of the record. While Skytrain (accumulation 14 cm ice eq. yr) does not match the accumulation rate of Law Dome, we present these new, high-resolution gas measurements over the period to work towards answering the following questions: (1) if the Law Dome record is correct, what caused this litude of CO2 change over a short timescale? (2) Does one of the records suffer from contamination? (3) Is our understanding of gas smoothing processes in these ice cores inaccurate? We will then use these measurements, from a well-validated & #8216 needle-crusher& #8217 CO2 device at the ice core labs at Oregon State University, USA, to validate a new semi-continuous ice-grating device (for which we present a preliminary outline) at the new ice core gas analysis lab at the British Antarctic Survey, UK.& &
Publisher: Research Square Platform LLC
Date: 26-07-2023
DOI: 10.21203/RS.3.RS-3170265/V1
Abstract: Ice core records of carbon dioxide (CO 2 ) throughout the last 2000 years provide context for the unprecedented anthropogenic rise in atmospheric CO 2 and insights into global carbon cycle dynamics on centennial and multidecadal timescales. Yet the atmospheric history of CO 2 remains uncertain in some time intervals. A particular source of debate is the exact timing and magnitude of the decrease in atmospheric CO 2 after 1550 CE. Here we present new ice core measurements of CO 2 and methane (CH 4 ) in the Skytrain Ice Rise ice core from 1450 to 1700 CE. The measurements, alongside analysis of the effects of gas record smoothing, suggest that a sudden decrease in ice core CO 2 around 1610 CE in one widely used record is most likely an artefact of a small number of anomalously low values. Instead, our analysis suggests a more gradual decrease in CO 2 of 0.5 ppm per decade between 1516 and 1670 CE, with an inferred land carbon sink of 2.7 PgC per decade. Furthermore, a rapid decrease in CO 2 at 1610 CE is incompatible with even the most extreme modelled scenarios for land-use change, whereas our data support scenarios of large-scale reorganization of land use in the Americas following New World-Old World contact.
Publisher: Springer Science and Business Media LLC
Date: 08-2017
DOI: 10.1038/NATURE23316
Abstract: Methane (CH
Publisher: American Association for the Advancement of Science (AAAS)
Date: 21-02-2020
Abstract: Methane is a potent greenhouse gas with large natural sources, reservoirs, and sinks. Dyonisius et al. found that methane emissions from old, cold-region carbon reservoirs like permafrost and methane hydrates were minor during the last deglaciation (see the Perspective by Dean). They analyzed the carbon isotopic composition of atmospheric methane trapped in bubbles in Antarctic ice and found that methane emissions from those old carbon sources during the warming interval were small. They argue that this finding suggests that methane emissions in response to future warming likely will not be as large as some have suggested. Science , this issue p. 907 see also p. 846
Publisher: Springer Science and Business Media LLC
Date: 12-2014
DOI: 10.1038/NATURE13971
Abstract: Nitrous oxide (N2O) is an important greenhouse gas and ozone-depleting substance that has anthropogenic as well as natural marine and terrestrial sources. The tropospheric N2O concentrations have varied substantially in the past in concert with changing climate on glacial-interglacial and millennial timescales. It is not well understood, however, how N2O emissions from marine and terrestrial sources change in response to varying environmental conditions. The distinct isotopic compositions of marine and terrestrial N2O sources can help disentangle the relative changes in marine and terrestrial N2O emissions during past climate variations. Here we present N2O concentration and isotopic data for the last deglaciation, from 16,000 to 10,000 years before present, retrieved from air bubbles trapped in polar ice at Taylor Glacier, Antarctica. With the help of our data and a box model of the N2O cycle, we find a 30 per cent increase in total N2O emissions from the late glacial to the interglacial, with terrestrial and marine emissions contributing equally to the overall increase and generally evolving in parallel over the last deglaciation, even though there is no a priori connection between the drivers of the two sources. However, we find that terrestrial emissions dominated on centennial timescales, consistent with a state-of-the-art dynamic global vegetation and land surface process model that suggests that during the last deglaciation emission changes were strongly influenced by temperature and precipitation patterns over land surfaces. The results improve our understanding of the drivers of natural N2O emissions and are consistent with the idea that natural N2O emissions will probably increase in response to anthropogenic warming.
Publisher: Springer Science and Business Media LLC
Date: 04-2015
DOI: 10.1038/NATURE14401
Abstract: The last glacial period exhibited abrupt Dansgaard-Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard-Oeschger cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard-Oeschger events, including the Bølling event Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard-Oeschger dynamics.
Publisher: American Geophysical Union (AGU)
Date: 10-08-2018
DOI: 10.1029/2018GL077881
Publisher: Springer Science and Business Media LLC
Date: 02-01-2020
Publisher: Springer Science and Business Media LLC
Date: 07-02-2020
Publisher: Copernicus GmbH
Date: 20-07-2017
Abstract: Abstract. Old ice for paleo-environmental studies, traditionally accessed through deep core drilling on domes and ridges on the large ice sheets, can also be retrieved at the surface from ice sheet margins and blue ice areas. The practically unlimited amount of ice available at these sites satisfies a need in the community for studies of trace components requiring large s le volumes. For margin sites to be useful as ancient ice archives, the ice stratigraphy needs to be understood and age models need to be established. We present measurements of trapped gases in ice from Taylor Glacier, Antarctica, to date the ice and assess the completeness of the stratigraphic section. Using δ18O of O2 and methane concentrations, we unambiguously identify ice from the last glacial cycle, covering every climate interval from the early Holocene to the penultimate interglacial. A high-resolution transect reveals the last deglaciation and the Last Glacial Maximum (LGM) in detail. We observe large-scale deformation in the form of folding, but in idual stratigraphic layers do not appear to have undergone irregular thinning. Rather, it appears that the entire LGM–deglaciation sequence has been transported from the interior of the ice sheet to the surface of Taylor Glacier relatively undisturbed. We present an age model that builds the foundation for gas studies on Taylor Glacier. A comparison with the Taylor Dome ice core confirms that the section we studied on Taylor Glacier is better suited for paleo-climate reconstructions of the LGM due to higher accumulation rates.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Thomas Bauska.