Best paper awards: first round announced
We are pleased to announce that the following papers have received the first of the ACEAS best paper awards:
Category: Postdoctoral Research Associates
Katharina Hochmuth
(J Whittaker, J., Huang, X.) (2024)
From Bottom Water Production to Warm Water Intrusions – The Cenozoic History of the Bottom-Current Evolution Offshore the Denman-Shackleton Region, East Antarctica. Paleoceanography and Paleoclimatology.
DOI: https://doi.org/10.1029/2024PA004948
Plain language summary
Today, warm salty water flows across the continental shelf of the Denman-Shackleton region in East Antarctica, causing increased melting and the retreat of the local ice sheet. We are investigating based on the sediment archive, how likely these intrusions have been in the geological past. Our analysis shows, that most likely, the Denman-Shackleton region has not experienced warm water intrusions for the majority of the Antarctic glaciation. During the early presence of the icesheet, the region contributed to the production of Antarctic bottom water, the globally dominating bottom water mass, a process which is not observed since and blocks intruding warm waters. With the transition to colder climates, the strength of the westward flowing ocean currents along the continental slope are managing the barrier between the cold shelf waters and the warmer waters of the deep sea. With a weakening of the current, the intrusion of warm waters onto the continental shelf become more common. This highlights, that the Denman/Shackleton region underwent a complete reversal of the ocean bottom current system throughout the history of the Antarctic ice sheet from the export of denser shelf waters to an increased potential of frequent warm waters on the continental shelf.
Zhi Li
(Matthew H. England, Sjoerd Groeskamp) (2024)
Abstract
The ocean absorbs >90% of anthropogenic heat in the Earth system, moderating global atmospheric warming. However, it remains unclear how this heat uptake is distributed by basin and across water masses. Here we analyze historical and recent observations to show that ocean heat uptake has accelerated dramatically since the 1990s, nearly doubling during 2010–2020 relative to 1990–2000. Of the total ocean heat uptake over the Argo era 2005–2020, about 89% can be found in global mode and intermediate water layers, spanning both hemispheres and both subtropical and subpolar mode waters. Due to anthropogenic warming, there are significant changes in the volume of these water-mass layers as they warm and freshen. After factoring out volumetric changes, the combined warming of these layers accounts for ~76% of global ocean warming. We further decompose these water-mass layers into regional water masses over the subtropical Pacific and Atlantic Oceans and in the Southern Ocean. This shows that regional mode and intermediate waters are responsible for a disproportionate fraction of total heat uptake compared to their volume, with important implications for understanding ongoing ocean warming, sea-level rise, and climate impacts.
Category: PhD students
Luca Magri
(J. M. Whittaker, M. F. Coffin, K. Hochmuth, D. Gürer, S. Williams, G. Bernardel, G. Uenzelmann-Neben) (2024)
Tectono-Stratigraphic Evolution of the Kerguelen Large Igneous Province: The Conjugate William’s Ridge – Broken Ridge Rifted Margins. Journal of Geophysical Research: Solid Earth.
DOI: https://doi.org/10.1029/2023JB027493
Plain language summary
Numerous investigations into the evolution of continental rift systems have advanced understanding of how the Earth's crust stretches and may eventually result in the formation of new ocean basins. However, these studies have not considered the case of thick mafic crust, sometimes including continental fragments. Here we focus on William’s Ridge (Kerguelen Plateau) and Broken Ridge, formed as a single feature, in the Southern Indian Ocean. We investigate how these features rifted, broke apart, and separated in the current conceptual framework of deformation migration. We use multichannel seismic reflection data, multibeam bathymetry data, drilling results, and magnetics data to interpret their structure, stratigraphy, and tectonics with the goal of explaining how the features evolved in time and space. Surprisingly, we find evidence for relatively weak magmatism despite the features being located near a mantle hotspot. Nevertheless, we suggest that the mantle hotspot influenced how the crust broke apart along different segments of the features' conjugate margins. We also find that the Australia and Antarctic tectonic plates, on which the features are now located, were moving laterally with respect to each other while rifting and breaking apart.
Ellie Ong
(Doddridge, E., Constantinou, N. C., Hogg, A. M., and England, M. H.) (2024)
Intrinsically Episodic Antarctic Shelf Intrusions of Circumpolar Deep Water via Canyons. Journal of Physical Oceanography.
DOI: https://doi.org/10.1175/JPO-D-23-0067.1
Abstract
The structure of the Antarctic Slope Current at the continental shelf is crucial in governing the poleward transport of warm water. Canyons on the continental slope may provide a pathway for warm water to cross the slope current and intrude onto the continental shelf underneath ice shelves, which can increase rates of ice shelf melting, leading to reduced buttressing of ice shelves, accelerating glacial flow and hence increased sea level rise. Observations and modeling studies of the Antarctic Slope Current and cross-shelf warm water intrusions are limited, particularly in the East Antarctica region. To explore this topic, an idealized configuration of the Antarctic Slope Current is developed, using an eddy-resolving isopycnal model that emulates the dynamics and topography of the East Antarctic sector. Warm water intrusions via canyons are found to occur in discrete episodes of large onshore flow induced by eddies, even in the absence of any temporal variability in external forcings, demonstrating the intrinsic nature of these intrusions to the slope current system. Canyon width is found to play a key role in modulating cross-shelf exchanges; warm water transport through narrower canyons is more irregular than transport through wider canyons. The intrinsically episodic cross-shelf transport is found to be driven by feedbacks between wind energy input and eddy generation in the Antarctic Slope Current. Improved understanding of the intrinsic variability of warm water intrusions can help guide future observational and modeling studies in the analysis of eddy impacts on Antarctic shelf circulation.
Congratulations to Katharina, Zhi, Luca and Ellie!
Nominations will be called for the next round of prizes in 2025.
