scholarly journals Simulated melt rates for the Totten and Dalton ice shelves

Ocean Science ◽  
2014 ◽  
Vol 10 (3) ◽  
pp. 267-279 ◽  
Author(s):  
D. E. Gwyther ◽  
B. K. Galton-Fenzi ◽  
J. R. Hunter ◽  
J. L. Roberts
Keyword(s):  
Mass Loss ◽  
Current Flow ◽  
Ocean Model ◽  
Warm Water ◽  
Coastal Current ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Oceanic Forcing ◽  
Basal Melting ◽  
Continental Shelf Break

Abstract. The Totten Glacier is rapidly losing mass. It has been suggested that this mass loss is driven by changes in oceanic forcing; however, the details of the ice–ocean interaction are unknown. Here we present results from an ice shelf–ocean model of the region that includes the Totten, Dalton and Moscow University ice shelves, based on the Regional Oceanic Modeling System for the period 1992–2007. Simulated area-averaged basal melt rates (net basal mass loss) for the Totten and Dalton ice shelves are 9.1 m ice yr−1 (44.5 Gt ice yr−1) and 10.1 m ice yr−1 (46.6 Gt ice yr−1), respectively. The melting of the ice shelves varies strongly on seasonal and interannual timescales. Basal melting (mass loss) from the Totten ice shelf spans a range of 5.7 m ice yr−1 (28 Gt ice yr−1) on interannual timescales and 3.4 m ice yr−1 (17 Gt ice yr−1) on seasonal timescales. This study links basal melt of the Totten and Dalton ice shelves to warm water intrusions across the continental shelf break and atmosphere–ocean heat exchange. Totten ice shelf melting is high when the nearby Dalton polynya interannual strength is below average, and vice versa. Melting of the Dalton ice shelf is primarily controlled by the strength of warm water intrusions across the Dalton rise and into the ice shelf cavity. During periods of strong westward coastal current flow, Dalton melt water flows directly under the Totten ice shelf further reducing melting. This is the first such modelling study of this region to provide a valuable framework for directing future observational and modelling efforts.

scholarly journals Simulated melt rates for the Totten and Dalton ice shelves

2013 ◽  
Vol 10 (6) ◽  
pp. 2109-2140 ◽  
Author(s):  
D. E. Gwyther ◽  
B. K. Galton-Fenzi ◽  
J. R. Hunter ◽  
J. L. Roberts
Keyword(s):  
Mass Loss ◽  
Current Flow ◽  
Ocean Model ◽  
Warm Water ◽  
Coastal Current ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Oceanic Forcing ◽  
Basal Melting ◽  
Continental Shelf Break

Abstract. The Totten Glacier drains a large proportion of the East Antarctic ice sheet, much of it marine based (grounded below sea level), and is rapidly losing mass. It has been suggested that this mass loss is driven by changes in oceanic forcing; however, the details of the ice-ocean interaction are unknown. Here we present results from an ice shelf-ocean model of the region that includes the Totten, Moscow University and Dalton Ice Shelves, based on the Regional Oceanic Modeling System for the period 1992–2007. Simulated area-averaged basal melt rates (net basal mass loss) for the Totten and Dalton ice shelves are 9.1 m ice yr−1 (44.5 Gt ice yr−1) and 10.1 m ice yr−1 (46.6 Gt ice yr−1), respectively. The melting of the ice shelves varies strongly on seasonal and interannual timescales. Basal melting (mass loss) from the Totten ice shelf spans a range of 5.7 m ice yr−1 (28 Gt ice yr−1) on interannual timescales and 3.4 m ice yr−1 (17 Gt ice yr−1) on seasonal timescales. This study links basal melt of the Totten and Dalton ice shelves to warm water intrusions across the continental shelf break and atmosphere-ocean heat exchange. Totten ice shelf melting is high when the nearby Dalton polynya interannual strength is below average, and vice versa. Melting of the Dalton ice shelf is primarily controlled by the strength of warm water intrusions across the Dalton Rise and into the ice shelf cavity. During periods of strong westwards coastal current flow, Dalton melt water flows directly under the Totten ice shelf further reducing melting. This is the first such modelling study of this region, providing a valuable framework for directing future observational and modelling efforts.

scholarly journals Modelling the long-term response of the Antarctic ice sheet to global warming

1998 ◽  
Vol 27 ◽  
pp. 161-168 ◽  
Author(s):  
Roland C. Warner ◽  
W.Κ. Budd
Keyword(s):  
Global Warming ◽  
Mass Loss ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
Basal Melting ◽  
The Antarctic ◽  
Term Response

The primary effects of global warming on the Antarctic ice sheet can involve increases in surface melt for limited areas at lower elevations, increases in net accumulation, and increased basal melting under floating ice. For moderate global wanning, resulting in ocean temperature increases of a few °C, the large- increase in basal melting can become the dominant factor in the long-term response of the ice sheet. The results from ice-sheet modelling show that the increased basal melt rates lead to a reduction of the ice shelves, increased strain rates and flow at the grounding lines, then thinning and floating of the marine ice sheets, with consequential further basal melting. The mass loss from basal melting is counteracted to some extent by the increased accumulation, but in the long term the area of ice cover decreases, particularly in West Antarctica, and the mass loss can dominate. The ice-sheet ice-shelf model of Budd and others (1994) with 20 km resolution has been modified and used to carry out a number of sensitivity studies of the long-term response of the ice sheet to prescribed amounts of global warming. The changes in the ice sheet are computed out to near-equilibrium, but most of the changes take place with in the first lew thousand years. For a global mean temperature increase of 3°C with an ice-shelf basal melt rate of 5 m a−1 the ice shelves disappear with in the first few hundred years, and the marine-based parts of the ice sheet thin and retreat. By 2000 years the West Antarctic region is reduced to a number of small, isolated ice caps based on the bedrock regions which are near or above sea level. This allows the warmer surface ocean water to circulate through the archipelago in summer, causing a large change to the local climate of the region.

scholarly journals Brief communication: A submarine wall protecting the Amundsen Sea intensifies melting of neighboring ice shelves

2019 ◽  
Vol 13 (9) ◽  
pp. 2317-2324 ◽  
Author(s):  
Özgür Gürses ◽  
Vanessa Kolatschek ◽  
Qiang Wang ◽  
Christian Bernd Rodehacke
Keyword(s):  
Ocean Model ◽  
Warm Water ◽  
Ice Shelf ◽  
The West ◽  
Amundsen Sea ◽  
West Antarctic Ice Sheet ◽  
Ice Shelves ◽  
West Antarctic ◽  
Antarctic Continent ◽  
Subsurface Cavities

Abstract. Disintegration of ice shelves in the Amundsen Sea, in front of the West Antarctic Ice Sheet, has the potential to cause sea level rise by inducing an acceleration of ice discharge from upstream grounded ice. Moore et al. (2018) proposed that using a submarine wall to block the penetration of warm water into the subsurface cavities of these ice shelves could reduce this risk. We use a global sea ice–ocean model to show that a wall shielding the Amundsen Sea below 350 m depth successfully suppresses the inflow of warm water and reduces ice shelf melting. However, these warm water masses get redirected towards neighboring ice shelves, which reduces the net effectiveness of the wall. The ice loss is reduced by 10 %, integrated over the entire Antarctic continent.

scholarly journals Intercomparison of Antarctic ice-shelf, ocean, and sea-ice interactions simulated by MetROMS-iceshelf and FESOM 1.4

2018 ◽  
Vol 11 (4) ◽  
pp. 1257-1292 ◽  
Author(s):  
Kaitlin A. Naughten ◽  
Katrin J. Meissner ◽  
Benjamin K. Galton-Fenzi ◽  
Matthew H. England ◽  
Ralph Timmermann ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Water Mass ◽  
Horizontal Resolution ◽  
Ocean Model ◽  
Small Scale ◽  
Ice Shelf ◽  
Vertical Coordinate ◽  
Ice Shelves ◽  
Basal Melting

Abstract. An increasing number of Southern Ocean models now include Antarctic ice-shelf cavities, and simulate thermodynamics at the ice-shelf/ocean interface. This adds another level of complexity to Southern Ocean simulations, as ice shelves interact directly with the ocean and indirectly with sea ice. Here, we present the first model intercomparison and evaluation of present-day ocean/sea-ice/ice-shelf interactions, as simulated by two models: a circumpolar Antarctic configuration of MetROMS (ROMS: Regional Ocean Modelling System coupled to CICE: Community Ice CodE) and the global model FESOM (Finite Element Sea-ice Ocean Model), where the latter is run at two different levels of horizontal resolution. From a circumpolar Antarctic perspective, we compare and evaluate simulated ice-shelf basal melting and sub-ice-shelf circulation, as well as sea-ice properties and Southern Ocean water mass characteristics as they influence the sub-ice-shelf processes. Despite their differing numerical methods, the two models produce broadly similar results and share similar biases in many cases. Both models reproduce many key features of observations but struggle to reproduce others, such as the high melt rates observed in the small warm-cavity ice shelves of the Amundsen and Bellingshausen seas. Several differences in model design show a particular influence on the simulations. For example, FESOM's greater topographic smoothing can alter the geometry of some ice-shelf cavities enough to affect their melt rates; this improves at higher resolution, since less smoothing is required. In the interior Southern Ocean, the vertical coordinate system affects the degree of water mass erosion due to spurious diapycnal mixing, with MetROMS' terrain-following coordinate leading to more erosion than FESOM's z coordinate. Finally, increased horizontal resolution in FESOM leads to higher basal melt rates for small ice shelves, through a combination of stronger circulation and small-scale intrusions of warm water from offshore.

scholarly journals Impact of ice-shelf basal melting on inland ice-sheet thickness: a model study

2012 ◽  
Vol 53 (60) ◽  
pp. 129-135 ◽  
Author(s):  
Jürgen Determann ◽  
Malte Thoma ◽  
Klaus Grosfeld ◽  
Sylvia Massmann
Keyword(s):  
Mass Loss ◽  
Sea Level ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
Ice Shelf ◽  
Ice Flow ◽  
Ice Shelves ◽  
Ice Volume ◽  
Basal Melting ◽  
The Impact

AbstractIce flow from the ice sheets to the ocean contains the maximum potential contributing to future eustatic sea-level rise. In Antarctica most mass fluxes occur via the extended ice-shelf regions covering more than half the Antarctic coastline. The most extended ice shelves are the Filchner–Ronne and Ross Ice Shelves, which contribute ~30% to the total mass loss caused by basal melting. Basal melt rates here show small to moderate average amplitudes of <0.5ma–1. By comparison, the smaller but most vulnerable ice shelves in the Amundsen and Bellinghausen Seas show much higher melt rates (up to 30 ma–1), but overall basal mass loss is comparably small due to the small size of the ice shelves. The pivotal question for both characteristic ice-shelf regions, however, is the impact of ocean melting, and, coevally, change in ice-shelf thickness, on the flow dynamics of the hinterland ice masses. In theory, ice-shelf back-pressure acts to stabilize the ice sheet, and thus the ice volume stored above sea level. We use the three-dimensional (3-D) thermomechanical ice-flow model RIMBAY to investigate the ice flow in a regularly shaped model domain, including ice-sheet, ice-shelf and open-ocean regions. By using melting scenarios for perturbation studies, we find a hysteresis-like behaviour. The experiments show that the system regains its initial state when perturbations are switched off. Average basal melt rates of up to 2 ma–1 as well as spatially variable melting calculated by our 3-D ocean model ROMBAX act as basal boundary conditions in time-dependent model studies. Changes in ice volume and grounding-line position are monitored after 1000 years of modelling and reveal mass losses of up to 40 Gt a–1.

scholarly journals Atmospheric and oceanic forcing of Larsen C Ice Shelf thinning

2015 ◽  
Vol 9 (1) ◽  
pp. 251-299 ◽  
Author(s):  
P. R. Holland ◽  
A. Brisbourne ◽  
H. F. J. Corr ◽  
D. McGrath ◽  
K. Purdon ◽  
...  
Keyword(s):  
High Surface ◽  
Strain Rates ◽  
Antarctic Bottom Water ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Flow Perturbation ◽  
Oceanic Forcing ◽  
Novel Method ◽  
Basal Melting ◽  
The Antarctic

Abstract. The catastrophic collapses of Larsen A and B ice shelves on the eastern Antarctic Peninsula have caused their tributary glaciers to accelerate, contributing to sea-level rise and freshening the Antarctic Bottom Water formed nearby. The surface of Larsen C Ice Shelf (LCIS), the largest ice shelf on the peninsula, is lowering. This could be caused by unbalanced ocean melting (ice loss) or enhanced firn melting and compaction (englacial air loss). Using a novel method to analyse eight radar surveys, this study derives separate estimates of ice and air thickness changes during a 15 year period. The uncertainties are considerable, but the primary estimate is that the surveyed lowering (0.066 ± 0.017 m yr−1) is caused by both ice loss (0.28 ± 0.18 m yr−1) and firn air loss (0.037 ± 0.026 m yr−1). Though the ice loss is much larger, ice and air loss contribute approximately equally to the lowering. The ice loss could be explained by high basal melting and/or ice divergence, and the air loss by low surface accumulation or high surface melting and/or compaction. The primary estimate therefore requires that at least two forcings caused the surveyed lowering. Mechanisms are discussed by which LCIS stability could be compromised in future, suggesting destabilisation timescales of a few centuries. The most rapid pathways to collapse are offered by a flow perturbation arising from the ungrounding of LCIS from Bawden Ice Rise, or ice-front retreat past a "compressive arch" in strain rates.

scholarly journals Ice-shelf changes in Pine Island Bay, Antarctica, 1947-2000

2002 ◽  
Vol 48 (161) ◽  
pp. 247-256 ◽  
Author(s):  
Eric Rignot
Keyword(s):  
Aerial Photographs ◽  
Line Center ◽  
Ice Shelf ◽  
Temperature Dependent ◽  
Ice Shelves ◽  
Front Position ◽  
Limit Of Viability ◽  
Oceanic Forcing ◽  
Slow Moving ◽  
Basal Melting

AbstractAerial photographs from 1947 and 1966, satellite optical imagery from 1973 and 1980, and interferometric synthetic aperture radar (InSAR) data from 1992, 1996 and 2000 are employed to detect ice-shelf changes in Pine Island Bay, Antarctica. The front position of the fast-flowing central ice shelf did not migrate discernibly over the past 50 years. New cracks and rifts appeared in the 1990s, however, that reveal a major weakening of the ice shelf. At the grounding-line center, the ice shelf thinned 21 m in 8 years. The northern, slow-moving ice shelf also shows signs of decay: (1) its calving front is retreating at an accelerating rate; and (2) the ice shelf is slowly unpinning from its bedrock anchors. These changes are taking place in a region well beyond the temperature-dependent limit of viability of ice shelves, and hence differ from those observed along the Antarctica Peninsula. They are likely due to a change in oceanic forcing, not to a change in air temperature. One possibility is that the documented intrusion of warm circumpolar deep water on the continental shelf has increased basal melting compared to that required to maintain the ice shelf in a state of mass balance, and that this has triggered a general retreat of ice in this sector.

scholarly journals Intercomparison of Antarctic ice shelf, ocean, and sea ice interactions simulated by two models

2017 ◽  
Author(s):  
Kaitlin A. Naughten ◽  
Katrin J. Meissner ◽  
Benjamin K. Galton-Fenzi ◽  
Matthew H. England ◽  
Ralph Timmermann ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Water Mass ◽  
Horizontal Resolution ◽  
Ocean Model ◽  
Small Scale ◽  
Ice Shelf ◽  
Vertical Coordinate ◽  
Ice Shelves ◽  
Basal Melting

Abstract. An increasing number of Southern Ocean models now include Antarctic ice shelf cavities, and simulate thermodynamics at the ice-shelf/ocean interface. This adds another level of complexity to Southern Ocean simulations, as ice shelves interact directly with the ocean and indirectly with sea ice. Here we present the first published model intercomparison and evaluation of present-day ocean/sea-ice/ice-shelf interactions, as simulated by two models: a circumpolar Antarctic configuration of MetROMS (ROMS: Regional Ocean Modelling System coupled to CICE: Community Ice CodE) and the global model FESOM (Finite Element Sea-ice/ice-shelf Ocean Model), where the latter is run at two different levels of horizontal resolution. From a circumpolar Antarctic perspective, we compare and evaluate simulated ice shelf basal melting and sub-ice shelf circulation, as well as sea ice properties and Southern Ocean water mass characteristics as they influence the sub-ice shelf processes. Despite their differing numerical methods, the two models produce broadly similar results, and share similar biases in many cases. Both models reproduce many key features of observations, but struggle to reproduce others, such as the high melt rates observed in the small warm-cavity ice shelves of the Amundsen and Bellingshausen Seas. Several differences in model design show a particular influence on the simulations. For example, FESOM's greater topographic smoothing can alter the geometry of some ice shelf cavities enough to affect their melt rates; this improves at higher resolution, since less smoothing is required. In the interior Southern Ocean, the vertical coordinate system affects the degree of water mass erosion due to spurious diapycnal mixing, with MetROMS' terrain-following coordinates leading to more erosion than FESOM's z-coordinates. Finally, increased horizontal resolution in FESOM leads to higher basal melt rates for small ice shelves, through a combination of stronger circulation and small-scale intrusions of warm water from offshore.

scholarly journals Brief communication: A submarine wall protecting the Amundsen Sea intensifies melting of neighboring ice shelves

2019 ◽  
Author(s):  
Özgür Gürses ◽  
Vanessa Kolatschek ◽  
Qiang Wang ◽  
Christian B. Rodehacke
Keyword(s):  
Sea Ice ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ocean Model ◽  
Warm Water ◽  
Ice Shelf ◽  
Ice Streams ◽  
Amundsen Sea ◽  
Ice Shelves

Abstract. Disintegration of ice shelves in the Amundsen Sea has the potential to cause sea level rise by inducing an acceleration of grounded ice streams. Moore et al. (2018) proposed that using a submarine wall to block the penetration of warm water into the ice shelf cavities could reduce this risk. We use a global sea ice-ocean model to show that a wall shielding the Amundsen Sea below 350 m depth successfully suppresses the inflow of warm water and reduces ice shelf melting. However, the warm water gets redirected towards neighboring ice shelves, which reduces the effectiveness of the wall.

scholarly journals Thermohaline structure and circulation beneath the Langhovde Glacier ice shelf in East Antarctica

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Masahiro Minowa ◽  
Shin Sugiyama ◽  
Masato Ito ◽  
Shiori Yamane ◽  
Shigeru Aoki
Keyword(s):  
Freezing Point ◽  
East Antarctica ◽  
Ice Shelf ◽  
Rate Estimate ◽  
Ice Shelves ◽  
Plume Water ◽  
Warm Deep Water ◽  
Glacier Ice ◽  
Basal Melting

AbstractBasal melting of ice shelves is considered to be the principal driver of recent ice mass loss in Antarctica. Nevertheless, in-situ oceanic data covering the extensive areas of a subshelf cavity are sparse. Here we show comprehensive structures of temperature, salinity and current measured in January 2018 through four boreholes drilled at a ~3-km-long ice shelf of Langhovde Glacier in East Antarctica. The measurements were performed in 302–12 m-thick ocean cavity beneath 234–412 m-thick ice shelf. The data indicate that Modified Warm Deep Water is transported into the grounding zone beneath a stratified buoyant plume. Water at the ice-ocean interface was warmer than the in-situ freezing point by 0.65–0.95°C, leading to a mean basal melt rate estimate of 1.42 m a−1. Our measurements indicate the existence of a density-driven water circulation in the cavity beneath the ice shelf of Langhovde Glacier, similar to that proposed for warm-ocean cavities of larger Antarctic ice shelves.

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