ORCID Profile
0000-0003-2789-2179
Current Organisation
University of Tasmania
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Publisher: Springer Science and Business Media LLC
Date: 21-02-2022
DOI: 10.1038/S43247-022-00369-X
Abstract: The stability of the West Antarctic Ice Sheet is threatened by the incursion of warm Circumpolar Deepwater which flows southwards via cross-shelf troughs towards the coast there melting ice shelves. However, the onset of this oceanic forcing on the development and evolution of the West Antarctic Ice Sheet remains poorly understood. Here, we use single- and multichannel seismic reflection profiles to investigate the architecture of a sediment body on the shelf of the Amundsen Sea Embayment. We estimate the formation age of this sediment body to be around the Eocene-Oligocene Transition and find that it possesses the geometry and depositional pattern of a plastered sediment drift. We suggest this indicates a southward inflow of deep water which probably supplied heat and, thus, prevented West Antarctic Ice Sheet advance beyond the coast at this time. We conclude that the West Antarctic Ice Sheet has likely experienced a strong oceanic influence on its dynamics since its initial formation.
Publisher: American Geophysical Union (AGU)
Date: 08-2020
DOI: 10.1029/2020GC009122
Publisher: American Geophysical Union (AGU)
Date: 02-2023
DOI: 10.1029/2022PA004438
Abstract: Based on inferences from proxy records the Miocene (23.03–5.33 Ma) was a time of lified polar warmth compared to today. However, it remains a challenge to simulate a warm Miocene climate and pronounced polar warmth at reconstructed Miocene CO 2 concentrations. Using a state‐of‐the‐art Earth‐System‐Model, we implement a high‐resolution paleobathymetry and simulate Miocene climate at different atmospheric CO 2 concentrations. We estimate global mean surface warming of +3.1°C relative to the preindustrial at a CO 2 level of 450 ppm. An increase of atmospheric CO 2 from 280 to 450 ppm provides an in idual warming of ∼1.4°C, which is as strong as all other Miocene forcing contributions combined. Substantial changes in surface albedo are vital to explain Miocene surface warming. Simulated surface temperatures fit well with proxy reconstructions at low‐ to mid‐latitudes. The high latitude cooling bias becomes less pronounced for higher atmospheric CO 2 concentrations. At such CO 2 levels simulated Miocene climate shows a reduced polar lification, linked to a breakdown of seasonality in the Arctic Ocean. A pronounced warming in boreal fall is detected for a CO 2 increase from 280 to 450 ppm, in comparison to weaker warming for CO 2 changes from 450 to 720 ppm. Moreover, a pronounced warming in winter is detected for a CO 2 increase from 450 to 720 ppm, in contrast to a moderate summer temperature increase, which is accompanied by a strong sea‐ice concentration decline that promotes cloud formation in summer via enhanced moisture availability. As a consequence planetary albedo increases and d ens the temperature response to CO 2 forcing at a warmer Miocene background climate.
Publisher: Elsevier
Date: 2022
Publisher: Elsevier BV
Date: 04-2019
Publisher: Copernicus GmbH
Date: 08-06-2023
DOI: 10.5194/EGUSPHERE-2023-872
Abstract: Abstract. The largest regional drivers of current surface elevation increases in the Antarctic Ice Sheet are associated with ice flow reconfiguration in previously active ice streams, highlighting the important role of ice dynamics in responding to climate change. Here, we investigate controls on the evolution of the flow configuration of the Vanderford and Totten Glaciers – key outlet glaciers of the Aurora Subglacial Basin, the most rapidly thinning region of the East Antarctic Ice Sheet. We review factors that influence the ice flow in this region, and use an ice sheet model to investigate the sensitivity of the catchment ide location to thinning at Vanderford Glacier associated with ongoing retreat, and thickening at Totten Glacier associated with an intensification of the east-west snowfall gradient. The present-day catchment ide between the Totten and Vanderford Glaciers is not constrained by the geology or topography, but is determined by the large-scale ice sheet geometry and its long-term evolution in response to climate forcing. Furthermore, the catchment ide is subject to migration under relatively small changes in surface elevation, leading to ice flow and basal water piracy from Totten to Vanderford Glacier. Our findings show that ice flow reconfigurations do not only occur in regions of West Antarctica like the Siple Coast, but also in the east, motivating further investigations of past, and potential for future, ice flow reconfigurations around the whole Antarctic coastline. Such modelling of ice flow and basal water piracy may require coupled ice sheet thermomechanical and subglacial hydrology models, constrained by field observations of subglacial conditions. Our results also have implications for ice sheet mass budget studies that integrate over catchments, and the validity of the zero flow assumption when selecting sites for ice core records of past climate.
Publisher: International Ocean Discovery Program
Date: 11-09-2023
Publisher: Elsevier BV
Date: 02-2020
Publisher: Springer Science and Business Media LLC
Date: 09-11-2022
DOI: 10.1038/S41467-022-34623-9
Abstract: Crossing a key atmospheric CO 2 threshold triggered a fundamental global climate reorganisation ~34 million years ago (Ma) establishing permanent Antarctic ice sheets. Curiously, a more dramatic CO 2 decline (~800–400 ppm by the Early Oligocene(~27 Ma)), postdates initial ice sheet expansion but the mechanisms driving this later, rapid drop in atmospheric carbon during the early Oligocene remains elusive and controversial. Here we use marine seismic reflection and borehole data to reveal an unprecedented accumulation of early Oligocene strata (up to 2.2 km thick over 1500 × 500 km) with a major biogenic component in the Australian Southern Ocean. High-resolution ocean simulations demonstrate that a tectonically-driven, one-off reorganisation of ocean currents, caused a unique period where current instability coincided with high nutrient input from the Antarctic continent. This unrepeated and short-lived environment favoured extreme bioproductivity and enhanced sediment burial. The size and rapid accumulation of this sediment package potentially holds ~1.067 × 10 15 kg of the ‘missing carbon’ sequestered during the decline from an Eocene high CO 2 -world to a mid-Oligocene medium CO 2 -world, highlighting the exceptional role of the Southern Ocean in modulating long-term climate.
Publisher: Elsevier
Date: 2022
Publisher: American Association for the Advancement of Science (AAAS)
Date: 29-05-2020
Abstract: High mantle P-wave speeds beneath oceanic plateaus define a new strain fabric indicative of flow in the head of a superplume.
Publisher: Elsevier BV
Date: 2019
Publisher: Geological Society of London
Date: 2013
DOI: 10.1144/SP381.21
Publisher: Springer Science and Business Media LLC
Date: 11-09-2023
Publisher: American Geophysical Union (AGU)
Date: 02-2017
DOI: 10.1002/2016TC004333
Publisher: Springer Science and Business Media LLC
Date: 04-2020
Publisher: Elsevier BV
Date: 2019
Publisher: American Geophysical Union (AGU)
Date: 11-2015
DOI: 10.1002/2015GC006036
Publisher: Elsevier BV
Date: 10-2013
Publisher: Copernicus GmbH
Date: 15-06-2018
Abstract: Abstract. Pine Island Glacier is the largest current Antarctic contributor to sea-level rise. Its ice loss has substantially increased over the last 25 years through thinning, acceleration and grounding line retreat. However, the calving line positions of the stabilising ice shelf did not show any trend within the observational record (last 70 years) until calving in 2015 led to unprecedented retreat and changed the alignment of the calving front. Bathymetric surveying revealed a ridge below the former ice shelf and two shallower highs to the north. Satellite imagery shows that ice contact on the ridge was likely lost in 2006 but was followed by intermittent contact resulting in back stress fluctuations on the ice shelf. Continuing ice-shelf flow also led to occasional ice-shelf contact with the northern bathymetric highs, which initiated rift formation that led to calving. The observations show that bathymetry is an important factor in initiating calving events.
Publisher: American Geophysical Union (AGU)
Date: 04-2019
DOI: 10.1029/2018GC008115
Publisher: Elsevier BV
Date: 12-2019
Publisher: Springer Science and Business Media LLC
Date: 09-11-2021
DOI: 10.1038/S41467-021-26658-1
Abstract: Declining atmospheric CO 2 concentrations are considered the primary driver for the Cenozoic Greenhouse-Icehouse transition, ~34 million years ago. A role for tectonically opening Southern Ocean gateways, initiating the onset of a thermally isolating Antarctic Circumpolar Current, has been disputed as ocean models have not reproduced expected heat transport to the Antarctic coast. Here we use high-resolution ocean simulations with detailed paleobathymetry to demonstrate that tectonics did play a fundamental role in reorganising Southern Ocean circulation patterns and heat transport, consistent with available proxy data. When at least one gateway (Tasmanian or Drake) is shallow (300 m), gyres transport warm waters towards Antarctica. When the second gateway subsides below 300 m, these gyres weaken and cause a dramatic cooling (average of 2–4 °C, up to 5 °C) of Antarctic surface waters whilst the ACC remains weak. Our results demonstrate that tectonic changes are crucial for Southern Ocean climate change and should be carefully considered in constraining long-term climate sensitivity to CO 2 .
Location: United Kingdom of Great Britain and Northern Ireland
Location: Germany
No related grants have been discovered for Katharina Hochmuth.