ORCID Profile
0000-0001-8624-365X
Current Organisations
Australian National University
,
Northern Illinois University
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Publisher: American Geophysical Union (AGU)
Date: 26-08-2023
DOI: 10.1029/2023GL104834
Abstract: The Antarctic Slope Current is guided by the topographic gradient of the Antarctic continental slope and creates a dynamical barrier between the continental shelf and the open ocean. The current's vertical structure varies around the continent affecting cross‐slope water mass exchange with consequences for Antarctic mass loss, ventilation of the deep ocean, and carbon uptake. The Antarctic Slope Current is surface‐intensified in many regions but bottom‐intensified in regions of dense overflows. This study investigates the role of dense overflows in modifying the dynamics of the bottom‐intensified flow using a 0.1° global ocean‐sea ice model. The occurrence of bottom‐intensification is tightly linked with dense overflows and bottom speeds correlate with dense overflows on interannual time scales. A lack of vertical connectivity between the bottom and surface flow, however, suggests that the along‐slope bottom water flows are coincidentally co‐located with the Antarctic Slope Current, rather than dynamically a part of the current.
Publisher: Elsevier BV
Date: 03-2020
Publisher: Springer Science and Business Media LLC
Date: 24-03-2016
Publisher: Springer Science and Business Media LLC
Date: 04-04-2016
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-13947
Abstract: & & & span& & span& The basal melt rate of Antarctica's ice shelves is largely controlled by heat delivered from the Southern Ocean to the Antarctic continental shelf. The Antarctic Slope Current (ASC) is an almost circumpolar feature that encircles Antarctica along the continental shelf break in an anti-clockwise direction. Because the circulation is to first order oriented along the topographic slope, it inhibits exchange of water masses between the Southern Ocean and the Antarctic continental shelf and thereby impacts cross-slope heat supply. Direct observations of the ASC system are sparse, but indicate a highly variable flow field both in time and space. Given the importance of the circulation near the shelf break for cross-shelf exchange of heat, it is timely to further improve our knowledge of the ASC system. This study makes use of the global ocean-sea ice model ACCESS-OM2-01 with a 1/10 degree horizontal resolution and describes the spatial and temporal variability of the velocity field. We categorise the modelled ASC into three different regimes, similar to previous works for the associated Antarctic Slope Front: (i) A surface-intensified current found predominantly in East Antarctica, (ii) a bottom-intensified current found downstream of the dense shelf water formation sit& /span& & span& e& /span& & span& s in the Ross, Weddell, and Prydz Bay Seas, and (iii) a reversed current found in West Antarctica where the eastward flowing Antarctic Circumpolar Current impinges onto the continental shelf break. We find that the temporal variability of the Antarctic Slope Current varies between the regimes. In the bottom-intensified regions, the variability is set by the timing of the dense shelf water overflows, whereas the surface-intensified flow responds to the sub-monthly variability in the wind field.& /span& & /span& & &
Publisher: American Meteorological Society
Date: 15-09-2023
Abstract: Winds around the Antarctic continental margin are known to exert a strong control on the local ocean stratification and circulation. However, past work has largely focused on the ocean response to changing winds in limited regional sectors and the circumpolar dynamical response to polar wind change remains uncertain. In this work, we use a high-resolution global ocean–sea ice model to investigate how dense shelf water formation and the temperature of continental shelf waters respond to changes in the zonal and meridional components of the polar surface winds. Increasing the zonal easterly wind component drives an enhanced southward Ekman transport in the surface layer, raising sea level over the continental shelf and deepening coastal isopycnals. The downward isopycnal movement cools the continental shelf, as colder surface waters replace warmer waters below. However, in this model the zonal easterly winds do not impact the strength of the abyssal overturning circulation, in contrast to past idealized model studies. Instead, increasing the meridional wind speed strengthens the abyssal overturning circulation via a sea ice advection mechanism. Enhanced offshore meridional wind speed increases the northward export of sea ice, resulting in decreased sea ice thickness over the continental shelf. The reduction in sea ice coverage leads to increased air–sea heat loss, sea ice formation, brine rejection, dense shelf water formation, and abyssal overturning circulation. Increasing the meridional winds causes warming at depth over most of the continental shelf, due to a heat advection feedback associated with the enhanced overturning circulation.
Publisher: Elsevier BV
Date: 06-2018
Publisher: Springer Science and Business Media LLC
Date: 23-12-2015
Publisher: American Meteorological Society
Date: 12-2019
Abstract: The Antarctic Slope Front (ASF) is located along much of the Antarctic continental shelf break and helps to maintain a barrier to the movement of Circumpolar Deep Water (CDW) onto the continental shelf. The stability of the ASF has a major control on cross-shelf heat transport and ocean-driven basal melting of Antarctic ice shelves. Here, the ASF dynamics are investigated for continental shelves with weak dense shelf water (DSW) formation, which are thought to have a stable ASF, common for regions in East Antarctica. Using an ocean process model, this study demonstrates how offshore bottom Ekman transport of shelf waters leads to the development of a deep bottom mixed layer at the lower continental slope, and subsequently determines an intrinsic variability of the ASF. The ASF variability is characterized by instability events that affect the entire water column and occur every 5–10 years and last for approximately half a year. During these instability events, the cross-shelf density gradient weakens and CDW moves closer to the continent. Stronger winds increase the formation rate of the bottom mixed layer, which causes a subsequent increase of instability events. If the observed freshening trend of continental shelf waters leads to weaker DSW formation, more regions might be vulnerable for the ASF variability to develop in the future.
Publisher: American Meteorological Society
Date: 03-2022
Abstract: The Antarctic Slope Current (ASC) circumnavigates the Antarctic continent following the continental slope and separating the waters on the continental shelf from the deeper offshore Southern Ocean. Water mass exchanges across the continental slope are critical for the global climate as they impact the global overturning circulation and the mass balance of the Antarctic ice sheet via basal melting. Despite the ASC’s global importance, little is known about its spatial and subannual variability, as direct measurements of the velocity field are sparse. Here, we describe the ASC in a global eddying ocean–sea ice model and reveal its large-scale spatial variability by characterizing the continental slope using three regimes: the surface-intensified ASC, the bottom-intensified ASC, and the reversed ASC. Each ASC regime corresponds to a distinct classification of the density field as previously introduced in the literature, suggesting that the velocity and density fields are governed by the same leading-order dynamics around the Antarctic continental slope. Only the surface-intensified ASC regime has a strong seasonality. However, large temporal variability at a range of other time scales occurs across all regimes, including frequent reversals of the current. We anticipate our description of the ASC’s spatial and subannual variability will be helpful to guide future studies of the ASC aiming to advance our understanding of the region’s response to a changing climate.
Publisher: Springer Science and Business Media LLC
Date: 09-03-2016
Location: Brazil
Location: No location found
No related grants have been discovered for Wilma Huneke.