ORCID Profile
0000-0002-3314-484X
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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.
Physical Oceanography | Glaciology | Climate Change Processes | Oceanography
Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts) | Expanding Knowledge in the Environmental Sciences | Expanding Knowledge in the Earth Sciences |
Publisher: American Geophysical Union (AGU)
Date: 11-09-2023
DOI: 10.1029/2022GL097864
Publisher: American Geophysical Union (AGU)
Date: 08-2017
DOI: 10.1002/2017JC012925
Publisher: Cambridge University Press (CUP)
Date: 24-09-2020
DOI: 10.1017/AOG.2020.69
Abstract: Sea ice, which forms in polar and nonpolar areas, transmits light to ice-associated (sympagic) algal communities. To noninvasively study the distribution of sea-ice algae, empirical relations to estimate its biomass from under-ice hyperspectral irradiance have been developed in the Arctic and Antarctica but lack for nonpolar regions. This study examines relationships between normalised difference indices (NDI) calculated from hyperspectral transmittance and sympagic algal biomass in the nonpolar Saroma-ko Lagoon. We analysed physico-biogeochemical properties of snow and land-fast sea ice supporting 27 paired bio-optical measurements along three transects covering an area of over 250 m × 250 m in February 2019. Snow depth (0.08 ± 0.01 m) and ice-bottom brine volume fraction (0.21 ± 0.02) showed low (0.06) and high (0.58) correlations with sea-ice core bottom section chlorophyll a (Chl. a ), respectively. Spatial analyses unveiled the patch size of sea-ice Chl. a to be ~65 m, which is in the same range reported from previous studies. A selected NDI (669, 596 nm) explained 63% of algal biomass variability. This reflects the bio-optical properties and environmental conditions of the lagoon that favour the wavelength pair in the orange/red part of the spectrum and suggests the necessity of a specific bio-optical relationship for Saroma-ko Lagoon.
Publisher: Wiley
Date: 07-02-2022
Publisher: American Association for the Advancement of Science (AAAS)
Date: 11-06-2021
Abstract: Poleward expansion of the Antarctic Circumpolar Current warms the Antarctic continental margin.
Publisher: American Geophysical Union (AGU)
Date: 08-2020
DOI: 10.1029/2019JC015406
Publisher: American Geophysical Union (AGU)
Date: 27-12-2021
DOI: 10.1029/2021JC017953
Abstract: To quantitatively assess the inorganic carbon cycle in the eastern Indian sector of the Southern Ocean (80–150°E, south of 60°S), we measured ocean surface temperature, salinity, total alkalinity (TA), the partial pressure of carbon dioxide (pCO 2 ), and concentrations of chlorophyll‐ a (chl a ), dissolved inorganic carbon (DIC), and nutrients during the KY18 survey (December 2018–January 2019). The sea–air CO 2 flux in this region was −8.3 ± 12.7 mmol m −2 day −1 (−92.1 to +10.6 mmol m −2 day −1 ). The ocean was therefore a weak CO 2 sink. Based on the DIC and TA in the temperature minimum layer, we estimated the change of pCO 2 from winter to summer (δpCO 2 ) due to changes in water temperature, salinity, and biological activity (photosynthesis). The spatial distribution of pCO 2 in the western part (80–110°E) of the study area was mainly driven by biological activity, which decreased pCO 2 from December to early January, and in the eastern part (110–150°E) by temperature, which increased pCO 2 from January to February. We also examined the changes in the CO 2 concentrations (xCO 2 ) over time by comparing data from 1996 with our data (2018–2019). The oceanic and atmospheric xCO 2 increased by 23 and 45 ppm in 23 years, respectively. These changes of ocean xCO 2 were mainly driven by an increase in CO 2 uptake from the atmosphere as a result of the rise in atmospheric xCO 2 and increase in biological activity associated with the change in the water‐mass distribution.
Publisher: American Geophysical Union (AGU)
Date: 02-2023
DOI: 10.1029/2022JC019422
Abstract: Warm, salty Circumpolar Deep Water (CDW) is recognized as the primary driver for Antarctic glacial melt, but the mechanism by which it reaches the continental shelves remains highly uncertain from an observational standpoint. With the scarcity of eddy flux estimation in the Antarctic margin, we quantify the isopycnal diffusivity of CDW using hydrographic variability and satellite altimetry under the mixing length framework. For comparison, the spiciness and thickness are used as isopycnal tracers, and the two tracers yield qualitatively similar estimates. Over the Antarctic Circumpolar Current (ACC), variation of mixing length is generally aligned with the jet‐induced mixing suppression, including in areas where topography blocks the jet's influence. In contrast, the mixing length does not depend on the mean flow in the subpolar zone, likely reflecting the relatively quiescent flow regime. The estimated isopycnal diffusivity ranges from 100 to 500 m 2 s −1 south of the ACC. The eddy diffusivity tends to be enhanced where the gradient of isopycnal thickness becomes small and CDW intrudes onshore. The cross‐slope eddy CDW flux is estimated, and the associated onshore heat flux across is calculated as ∼3.6 TW in the eastern Indian sector. The eddy heat flux and coastal solar heating are generally balanced with cryospheric heat sinks including glacial melting and surface freezing, suggesting that the eddy advection is substantial for the onshore CDW flux. The thickness field is essential for determining mixing length and eddy fluxes in the subpolar zone, however this is not the case in the ACC domain.
Publisher: Wiley
Date: 27-10-2022
Publisher: Wiley
Date: 22-12-2021
Publisher: Springer Science and Business Media LLC
Date: 22-06-2022
DOI: 10.1038/S43247-022-00456-Z
Abstract: Melting ice shelves around Antarctica control the massive input of freshwater into the ocean and play an intricate role in global heat redistribution. The Amery Ice Shelf regulates wintertime sea-ice growth and dense shelf water formation. We investigated the role of warm Antarctic Surface Water in ice shelf melting and its impact on dense shelf water. Here we show that the coastal ocean in summer 2016/17 was almost sea-ice free, leading to higher surface water temperatures. The glacial meltwater fraction in surface water was the highest on record, hypothesised to be attributable to anomalous ice shelf melting. The excess heat and freshwater in early 2017 delayed the seasonal evolution of dense shelf water. Focused on ice shelf melting at depth, the importance and impacts of warming surface waters has been overlooked. In a warming climate, increased surface water heating will reduce coastal sea-ice production and potentially Antarctic Bottom Water formation.
Publisher: Wiley
Date: 28-01-2022
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-04-2018
Abstract: Glacial meltwater stops bottom-water formation, allowing warm ocean waters to reach Antarctic ice shelves and drive rapid melting.
Publisher: Springer Science and Business Media LLC
Date: 17-08-2023
DOI: 10.1038/S41467-023-39764-Z
Abstract: The Totten Glacier in East Antarctica, with an ice volume equivalent to .5 m of global sea-level rise, is grounded below sea level and, therefore, vulnerable to ocean forcing. Here, we use bathymetric and oceanographic observations from previously uns led parts of the Totten continental shelf to reveal on-shelf warm water pathways defined by deep topographic features. Access of warm water to the Totten Ice Shelf (TIS) cavity is facilitated by a deep shelf break, a broad and deep depression on the shelf, a cyclonic circulation that carries warm water to the inner shelf, and deep troughs that provide direct access to the TIS cavity. The temperature of the warmest water reaching the TIS cavity varies by ~0.8 °C on an interannual timescale. Numerical simulations constrained by the updated bathymetry demonstrate that the deep troughs play a critical role in regulating ocean heat transport to the TIS cavity and the subsequent basal melt of the ice shelf.
Publisher: American Geophysical Union (AGU)
Date: 09-2023
DOI: 10.1029/2022GB007510
Abstract: To clarify the impacts of basal melting of the Antarctic ice sheet and biological productivity on biogeochemical processes in Antarctic coastal waters, concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA), inorganic nutrients, chlorophyll a , and stable oxygen isotopic ratios (δ 18 O) were measured from the offshore slope to the ice front of the Totten Ice Shelf (TIS) during the spring/summer of 2018, 2019, and 2020. Modified Circumpolar Deep Water (mCDW) intruded onto the continental shelf off the TIS and flowed along bathymetric troughs into the TIS cavity, where it formed a buoyant mixture with glacial meltwater from the ice shelf base. Physical oceanographic processes mostly determined the distributions of DIC, TA, and nutrient concentrations. However, photosynthesis and dilution by meltwater from sea ice and the ice shelf base decreased DIC, TA, and nutrient concentrations in surface water near the ice front. These causes also reduced the CO 2 partial pressure in surface water by more than 100 μatm with respect to mCDW in austral summer of 2018 and 2020, and the surface water became a strong CO 2 sink for the atmosphere. Phytoplankton photosynthesis changed DIC and TA in a molar ratio of 106:16. Thus, CO 2 partial pressure decreased mostly as a result of photosynthesis while dilution by glacial and sea ice meltwater had a small effect. The nutrient consumption ratio suggested that photosynthesis was stimulated by iron in the water column, supplied to the surface layer via buoyancy‐driven upwelling and basal ice shelf meltwater in addition to sea ice meltwater.
Publisher: American Geophysical Union (AGU)
Date: 07-2022
DOI: 10.1029/2021JC018371
Abstract: We elucidated the effects of snow and remineralization processes on nutrient distributions in multi‐year landfast sea ice (fast ice) in Lützow‐Holm Bay, East Antarctica. Based on sea‐ice salinity, oxygen isotopic ratios, and thin section analyses, we found that the multi‐year fast ice grew upward due to the year‐by‐year accumulation of snow. Compared to ice of seawater origin, nutrient concentrations in shallow fast ice were low due to replacement by clean and fresh snow. In deeper ice of seawater origin (the lower half of the multi‐year fast ice column), remineralization was dominated by the degradation of organic matter. By comparison between first‐ and muti‐year ice, the biological uptake and the remineralization were dominated in relatively young ice and older ice, respectively, under the physical process of brine drainage.
No related organisations have been discovered for shigeru aoki.
Start Date: 08-2021
End Date: 12-2027
Amount: $20,000,000.00
Funder: Australian Research Council
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