ORCID Profile
0000-0002-6441-1496
Current Organisation
University of Southampton
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Publisher: American Meteorological Society
Date: 08-2021
Publisher: Springer Science and Business Media LLC
Date: 16-11-2020
Publisher: American Association for the Advancement of Science (AAAS)
Date: 02-12-2016
Abstract: Inflow of warm water drives rapid melt of the Totten Ice Shelf, demonstrating that this sector of East Antarctica is exposed to ocean heat.
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-8371
Abstract: & & & & & & & & Antarctic Bottom Water (AABW) supplies the lower limb of the global overturning circulation, ventilates the abyssal ocean and sequesters heat and carbon on multidecadal to millennial timescales. AABW originates on the Antarctic continental shelf, where strong winter cooling and brine released during sea ice formation produce Dense Shelf Water, which sinks to the deep ocean. The salinity, density and volume of AABW have decreased over the last 50 years, with the most marked changes observed in the Ross Sea. These changes have been attributed to increased melting of the Antarctic Ice Sheet. Here we use in situ observations to document a recovery in the salinity, density and thickness (that is, depth range) of AABW formed in the Ross Sea, with properties in 2018& #8211 similar to those observed in the 1990s. The recovery was caused by increased sea ice formation on the continental shelf. Increased sea ice formation was triggered by anomalous wind forcing associated with the unusual combination of positive Southern Annular Mode and extreme El Ni& #241 o conditions between 2015 and 2018. Our study highlights the sensitivity of AABW formation to remote forcing and shows that climate anomalies can drive episodic increases in local sea ice formation that counter the tendency for increased ice-sheet melt to reduce AABW formation.& & & / & & / & & / &
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-8902
Abstract: Warm ocean waters drive rapid ice-shelf melting in the Amundsen Sea. The ocean heat transport toward the ice shelves is associated with the Amundsen Undercurrent, a near-bottom current that flows eastward along the shelf break and transports warm waters onto the continental shelf via troughs. Here we use a regional ice-ocean model to show that, on decadal time scales, the undercurrent's variability is baroclinic (depth-dependent). Decadal ocean surface cooling in the tropical Pacific results in cyclonic wind anomalies over the Amundsen Sea. These wind anomalies drive a westward perturbation of the shelf-break surface& flow and an eastward anomaly (strengthening) of the undercurrent, leading to increased ice-shelf melting. This contrasts with shorter time scales, for which surface current and undercurrent covary, a barotropic (depth-independent) behavior previously assumed to apply at all time scales. This suggests that interior ocean processes mediate the decadal ice-shelf response in the Amundsen Sea to climate forcing.
Publisher: Springer Science and Business Media LLC
Date: 2020
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-7897
Abstract: & & Antarctic Bottom Water (AABW) is one of the most important deep water masses contributing to the lower limb of the global overturning circulation, which modulates the deep ocean ventilation and oceanic heat/carbon exchanges on multidecadal to millennial timescales. Weddell Sea Bottom Water (WSBW) is a key precursor of the AABW exported from the Weddell Sea. Its formation involves intense air-sea-ice interaction on the continental shelf that releases brine from sea ice formation, and occurs mostly in the austral winter. Here we report a distinct long-term volume decline of WSBW revealed by data collected along repeat occupations of World Ocean Circulation Experiment (WOCE) hydrographic sections. We estimate a & % reduction of WSBW volume since the early 1990s and a resultant widespread deep Weddell Sea warming associated with a basin-scale deepening of isopycnal surfaces. With the most significant volume reduction concentrating within the densest classes of WSBW and a concurrent decline of sea ice formation rate (& %) over the southwestern Weddell continental shelf inferred from remote-sensed sea ice concentration data, we propose that the observed WSBW volume reduction is likely to be driven by a multidecadal weakening of dense shelf water production due to the sea ice changes. Reanalysis atmospheric data and ice drift data suggest that the reduction of sea ice formation rate is predominantly linked to changes in wind-driven sea ice convergence in front of Ronne Ice Shelf and Berkner Bank, as a response to a vigorous Amundsen Sea Low deepening that is teleconnected to tropical Pacific SST variability, and associated with the local radiative forcing from long-term ozone depletion.& &
Publisher: American Geophysical Union (AGU)
Date: 06-2019
DOI: 10.1029/2018JC014634
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-3067
Abstract: & & The West Antarctic Ice Sheet is losing mass at an accelerating rate, contributing to sea level rise. Ocean forcing is considered to be the main driver of this mass loss, associated with warm intrusions of Circumpolar Deep Water onto the continental shelf. Here we describe these intrusions, focussing on the role of the Amundsen Undercurrent. The Amundsen Undercurrent is an eastward, bottom-intensified current located at the shelf break/upper slope that transports warm Circumpolar Deep Water. This current enters the continental shelf through deep canyons that connect the shelf break with ice shelf cavities, bringing oceanic heat to the base of the ice shelves. We use a regional ocean model to introduce the forcing mechanisms of the Amundsen Undercurrent and the drivers of its temporal variability. We conclude by discussing how this variability ultimately influences melting of ice shelves in the Amundsen Sea.& &
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-5080
Abstract: Deep convection from dense water formation in the Southern Ocean drives the lower limb of the global overturning circulation, sequesters anthropogenic heat and carbon from the atmosphere and ventilates the abyssal ocean. The rate and location of dense water formation and its trajectory to the deep ocean is determined by changes in ocean density and stratification and influenced by ocean-ice-atmosphere interactions such as polynya openings (both open-ocean and coastal), sea ice formation and ice shelf collapse.Signatures of deep convection are logistically difficult to measure. The highest-quality observations of water column density are currently provided by in-situ moorings and profiles from Argo floats or CTDs mounted on elephant seals (MEOP data[1]), but these data are spatially and temporally sparse. Satellite products providing complete coverage of high latitudes at regular repeat periods are becoming more readily available and offer an alternative method for capturing changes the extent and variability of deep-water formation in polar regions.& We compute steric height anomalies in the Southern Ocean from 2002-2018 using a novel method combining satellite altimetry and gravimetry data. We use these to explore density changes, focussing on deep water formation regions including the Weddell and Ross seas, the Adelie coastline and Amery shelf region, and infer multi-decadal changes in deep convective processes. Long term changes in the steric height anomalies can be linked to recorded ocean-ice events, such as the 2010 collapse of the Mertz glacier, the 2017 Maud Rise polynya and recent recovery of Ross Sea Bottom Water. The satellite-derived steric height anomalies have been validated against in-situ Argo and MEOP profiles and show good agreement in regions with a high data density. [1]eop-portal/
Publisher: The Oceanography Society
Date: 12-2016
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: American Association for the Advancement of Science (AAAS)
Date: 03-11-2017
Abstract: Wind upwells warm water from the deep ocean off the East Antarctic coast, leading to ice-shelf melt and glacier acceleration.
Publisher: American Geophysical Union (AGU)
Date: 05-2019
DOI: 10.1029/2019JC015071
Publisher: American Meteorological Society
Date: 05-2015
DOI: 10.1175/JTECH-D-14-00161.1
Abstract: A 1-yr experiment using a pressure-sensor-equipped inverted echo sounder (PIES) was conducted in Sermilik Fjord in southeastern Greenland (66°N, 38°E) from August 2011 to September 2012. Based on these high-latitude data, the interpretation of PIESs’ acoustic travel-time records from regions that are periodically ice covered were refined. In addition, new methods using PIESs for detecting icebergs and sea ice and for estimating iceberg drafts and drift speeds were developed and tested. During winter months, the PIES in Sermilik Fjord logged about 300 iceberg detections and recorded a 2-week period in early March of land-fast ice cover over the instrument site, consistent with satellite synthetic aperture radar (SAR) imagery. The deepest icebergs in the fjord were found to have keel depths greater than approximately 350 m. Average and maximum iceberg speeds were approximately 0.2 and 0.5 m s −1 , respectively. The maximum tidal range at the site was ±1.8 m and during neap tides the range was ±0.3 m, as shown by the PIES’s pressure record.
Publisher: Springer Science and Business Media LLC
Date: 12-06-2023
DOI: 10.1038/S41558-023-01695-4
Abstract: Antarctic Bottom Water (AABW) is pivotal for oceanic heat and carbon sequestrations on multidecadal to millennial timescales. The Weddell Sea contributes nearly a half of global AABW through Weddell Sea Deep Water and denser underlying Weddell Sea Bottom Water that form on the continental shelves via sea-ice production. Here we report an observed 30% reduction of Weddell Sea Bottom Water volume since 1992, with the largest decrease in the densest classes. This is probably driven by a multidecadal reduction in dense-water production over southern continental shelf associated with a % decline in the sea-ice formation rate. The ice production decrease is driven by northerly wind trend, related to a phase transition of the Interdecadal Pacific Oscillation since the early 1990s, superposed by Amundsen Sea Low intrinsic variability. These results reveal key influences on exported AABW to the Atlantic abyss and their sensitivity to large-scale, multidecadal climate variability.
Publisher: Springer Science and Business Media LLC
Date: 07-06-2022
DOI: 10.1038/S41597-022-01366-7
Abstract: The Southern Ocean surrounding Antarctica is a region that is key to a range of climatic and oceanographic processes with worldwide effects, and is characterised by high biological productivity and bio ersity. Since 2013, the International Bathymetric Chart of the Southern Ocean (IBCSO) has represented the most comprehensive compilation of bathymetry for the Southern Ocean south of 60°S. Recently, the IBCSO Project has combined its efforts with the Nippon Foundation – GEBCO Seabed 2030 Project supporting the goal of mapping the world’s oceans by 2030. New datasets initiated a second version of IBCSO (IBCSO v2). This version extends to 50°S (covering approximately 2.4 times the area of seafloor of the previous version) including the gateways of the Antarctic Circumpolar Current and the Antarctic circumpolar frontal systems. Due to increased (multibeam) data coverage, IBCSO v2 significantly improves the overall representation of the Southern Ocean seafloor and resolves many submarine landforms in more detail. This makes IBCSO v2 the most authoritative seafloor map of the area south of 50°S.
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-10635
Abstract: & & The marine-terminating glaciers of the Amundsen Sea are experiencing increased basal melting associated with an inflow of warm and salty water from the deep ocean onto the shelf via submarine glacial troughs.& Modelling work suggests that& variability in the transport of this source of heat across the shelf-break and onto the Dotson Trough in the& western& Amundsen Sea& is regulated by wind-driven changes in an eastward undercurrent& that flows& along the continental slope.& & & & What controls the strength and variability of the undercurrent,& however, is not well& documented due to a lack of observations in the region. Here, we use a 5-year mooring record of undercurrent velocity in the Dotson Trough in conjunction with a novel 16-year altimetric sea level product that includes measurements in regions of near-perennial ice cover to describe the connection between undercurrent variability and climate modes on seasonal to interannual time scales.& & & & We find a robust signature of the undercurrent variability that is linked to both a circumpolar coastal sea level signal as well as to the sea level in an offshore region in the Amundsen Sea. We discuss the implications of this undercurrent-sea level covariability in the context of atmospheric climate modes and we further explore what this link conveys about the undercurrent variability on interannual timescales by using of our full altimetry record.& &
Publisher: American Geophysical Union (AGU)
Date: 14-12-2022
DOI: 10.1029/2022GL100646
Abstract: Warm ocean waters drive rapid ice‐shelf melting in the Amundsen Sea. The ocean heat transport toward the ice shelves is associated with the Amundsen Undercurrent, a near‐bottom current that flows eastward along the shelf break and transports warm waters onto the continental shelf via troughs. Here we use a regional ice‐ocean model to show that, on decadal time scales, the undercurrent's variability is baroclinic (depth‐dependent). Decadal ocean surface cooling in the tropical Pacific results in cyclonic wind anomalies over the Amundsen Sea. These wind anomalies drive a westward perturbation of the shelf‐break surface flow and an eastward anomaly (strengthening) of the undercurrent, leading to increased ice‐shelf melting. This contrasts with shorter time scales, for which surface current and undercurrent covary, a barotropic (depth‐independent) behavior previously assumed to apply at all time scales. This suggests that interior ocean processes mediate the decadal ice‐shelf response in the Amundsen Sea to climate forcing.
Publisher: American Geophysical Union (AGU)
Date: 03-2017
DOI: 10.1002/2016JC012115
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Alessandro Silvano.