Modelling the ocean circulation and the basal melting in the Prydz Bay-Amery Ice Shelf system

2021 ◽  
Author(s):  
Jing Jin ◽  
Antony J. Payne ◽  
William Seviour ◽  
Christopher Bull
Keyword(s):  
Heat Transport ◽  
Ocean Circulation ◽  
Water Masses ◽  
Prydz Bay ◽  
Effect Of Temperature ◽  
Oceanic Circulation ◽  
Ice Shelf ◽  
Thermodynamic Structure ◽  
Amery Ice Shelf ◽  
Basal Melting

<p>The basal melting of the Amery Ice Shelf (AIS) in East Antarctica and its connections with the oceanic circulation are investigated by a regional ocean model. The simulated estimations of net melt rate over AIS from 1976 to 2005 vary from 1 to 2 m/yr depending primarily due to inflow of modified Circumpolar Deep Water (mCDW). Prydz Bay Eastern Costal Current (PBECC) and the eastern branch of Prydz Bay Gyre (PBG) are identified as two main mCDW intrusion pathways. The oceanic heat transport from both PBECC and PBG has significant seasonal variability, which is associated with the Antarctic Slope Current. The onshore heat transport has a long-lasting effect on basal melting. The basal melting is primarily driven by the inflowing water masses though a positive feedback mechanism. The intruding warm water masses destabilize the thermodynamic structure in the sub-ice shelf cavity therefore enhancing the overturning circulations, leading to further melting due to increasing heat transport. However, the inflowing saltier water masses due to sea-ice formation could offset the effect of temperature through stratifying the thermodynamic structure, then suppressing the overturning circulation and reducing the basal melting.</p>

scholarly journals Energetics of Eddy-Mean Flow Interactions in the Amery Ice Shelf Cavity

2021 ◽  
Vol 8 ◽  
Author(s):  
Yang Wu ◽  
Zhaomin Wang ◽  
Chengyan Liu ◽  
Liangjun Yan
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Ocean Circulation ◽  
Bottom Topography ◽  
Ocean Bottom ◽  
Mean Flow ◽  
Ice Shelf ◽  
Available Potential Energy ◽  
Amery Ice Shelf ◽  
Basal Melting

Previous studies demonstrated that eddy processes play an important role in ice shelf basal melting and the water mass properties of ice shelf cavities. However, the eddy energy generation and dissipation mechanisms in ice shelf cavities have not been studied systematically. The dynamic processes of the ocean circulation in the Amery Ice Shelf cavity are studied quantitatively through a Lorenz energy cycle approach for the first time by using the outputs of a high-resolution coupled regional ocean-sea ice-ice shelf model. Over the entire sub-ice-shelf cavity, mean available potential energy (MAPE) is the largest energy reservoir (112 TJ), followed by the mean kinetic energy (MKE, 70 TJ) and eddy available potential energy (EAPE, 10 TJ). The eddy kinetic energy (EKE) is the smallest pool (5.5 TJ), which is roughly 8% of the MKE, indicating significantly suppressed eddy activities by the drag stresses at ice shelf base and bottom topography. The total generation rate of available potential energy is about 1.0 GW, almost all of which is generated by basal melting and seawater refreezing, i.e., the so-called “ice pump.” The energy generated by ice pump is mainly dissipated by the ocean-ice shelf and ocean-bottom drag stresses, amounting to 0.3 GW and 0.2 GW, respectively. The EKE is generated through two pathways: the barotropic pathway MAPE→MKE→EKE (0.03 GW) and the baroclinic pathway MAPE→EAPE→EKE (0.2 GW). In addition to directly supplying the EAPE through baroclinic pathway (0.2 GW), MAPE also provides 0.5 GW of power to MKE to facilitate the barotropic pathway.

The effects of ocean warming on melting and ocean circulation under the Amery Ice Shelf, East Antarctica

1998 ◽  
Vol 27 ◽  
pp. 75-80 ◽  
Author(s):  
M.J.M. Williams ◽  
R. C. Warner ◽  
W. F. Budd
Keyword(s):  
Mass Balance ◽  
Ocean Circulation ◽  
Three Dimensional ◽  
Ocean Model ◽  
Ocean Warming ◽  
East Antarctica ◽  
Ice Shelf ◽  
Temperature Changes ◽  
Amery Ice Shelf ◽  
Basal Melting

Using a three-dimensional ocean model specially adapted to the ocean cavity under the Amery Ice Shelf, we investigated the present ocean circulation and pattern of ice-shelf basal melting and freezing, the differences which would result from temperature changes in the seas adjacent to the Amery Ice Shelf, and the ramifications of these changes for the mass balance of the ice shelf. Under present conditions we estimate the net loss from the Amery Ice Shelf from excess basal melting over freezing at approximately 7.8 Gt a−1. This comprises a gross loss of 11.4 Gt a−1 at a mean rate of 0.42 m a−1, which is partially offset by freezing-on of 3.6 Gt a−1, at a mean rate of 0.19 m a−1. When the adjacent seas were assumed to warm by 1°C, we found the net melt increased to 31.6 Gt a−1, comprising 34.6 Gt a−1 of gross melt and 3.0 Gt a−1 of freezing.

scholarly journals Ice-shelf basal channels in a coupled ice/ocean model

2012 ◽  
Vol 58 (212) ◽  
pp. 1227-1244 ◽  
Author(s):  
Carl V. Gladish ◽  
David M. Holland ◽  
Paul R. Holland ◽  
Stephen F. Price
Keyword(s):  
Ocean Circulation ◽  
Coupled System ◽  
Ocean Model ◽  
Subsurface Water ◽  
Ice Thickness ◽  
Ice Shelf ◽  
First Approximation ◽  
Grounding Line ◽  
History Of ◽  
Basal Melting

AbstractA numerical model for an interacting ice shelf and ocean is presented in which the ice- shelf base exhibits a channelized morphology similar to that observed beneath Petermann Gletscher’s (Greenland) floating ice shelf. Channels are initiated by irregularities in the ice along the grounding line and then enlarged by ocean melting. To a first approximation, spatially variable basal melting seaward of the grounding line acts as a steel-rule die or a stencil, imparting a channelized form to the ice base as it passes by. Ocean circulation in the region of high melt is inertial in the along-channel direction and geostrophically balanced in the transverse direction. Melt rates depend on the wavelength of imposed variations in ice thickness where it enters the shelf, with shorter wavelengths reducing overall melting. Petermann Gletscher’s narrow basal channels may therefore act to preserve the ice shelf against excessive melting. Overall melting in the model increases for a warming of the subsurface water. The same sensitivity holds for very slight cooling, but for cooling of a few tenths of a degree a reorganization of the spatial pattern of melting leads, surprisingly, to catastrophic thinning of the ice shelf 12 km from the grounding line. Subglacial discharge of fresh water along the grounding line increases overall melting. The eventual steady state depends on when discharge is initiated in the transient history of the ice, showing that multiple steady states of the coupled system exist in general.

scholarly journals An improved bathymetry compilation for the Bellingshausen Sea, Antarctica, to inform ice-sheet and ocean models

2010 ◽  
Vol 4 (4) ◽  
pp. 2079-2101 ◽  
Author(s):  
A. G. C. Graham ◽  
F. O. Nitsche ◽  
R. D. Larter
Keyword(s):  
Ocean Circulation ◽  
Ice Sheet ◽  
West Antarctica ◽  
Ice Shelf ◽  
Ice Streams ◽  
Ice Shelves ◽  
Sea Floor ◽  
Bellingshausen Sea ◽  
Warm Deep Water ◽  
Basal Melting

Abstract. The southern Bellingshausen Sea (SBS) is a rapidly-changing part of West Antarctica, where oceanic and atmospheric warming has led to the recent basal melting and break-up of the Wilkins ice shelf, the dynamic thinning of fringing glaciers, and sea-ice reduction. Accurate sea-floor morphology is vital for understanding the continued effects of each process upon changes within Antarctica's ice sheets. Here we present a new bathymetric grid for the SBS compiled from shipborne echo-sounder, spot-sounding and sub-ice measurements. The 1-km grid is the most detailed compilation for the SBS to-date, revealing large cross-shelf troughs, shallow banks, and deep inner-shelf basins that continue inland of coastal ice shelves. The troughs now serve as pathways which allow warm deep water to access the ice fronts in the SBS. Our dataset highlights areas still lacking bathymetric constraint, as well as regions for further investigation, including the likely routes of palaeo-ice streams. The new compilation is a major improvement upon previous grids and will be a key dataset for incorporating into simulations of ocean circulation, ice-sheet change and history. It will also serve forecasts of ice stability and future sea-level contributions from ice loss in West Antarctica, required for the next IPCC assessment report in 2013.

Representation of basal melting in idealised coupled ice sheet ocean models

2021 ◽  
Author(s):  
Chen Zhao ◽  
Rupert Gladstone ◽  
Ben Galton-Fenzi ◽  
David Gwyther
Keyword(s):  
Ocean Circulation ◽  
Critical Role ◽  
Ice Sheet ◽  
Ocean Model ◽  
Periodic Pattern ◽  
Regional Ocean Modeling System ◽  
Ice Shelf ◽  
Grounding Line ◽  
Ocean Models ◽  
Basal Melting

<p>The ocean-driven basal melting has important implications for the stability of ice shelves in Antarctic, which largely affects the ice sheet mass balance, ocean circulation, and subsequently global sea level rise. Due to the limited observations in the ice shelf cavities, the couple ice sheet ocean models have been playing a critical role in examining the processes governing basal melting. In this study we use the Framework for Ice Sheet-Ocean Coupling (FISOC) to couple the Elmer/Ice full-stokes ice sheet model and the Regional Ocean Modeling System (ROMS) ocean model to model ice shelf/ocean interactions for an idealised three-dimensional domain. Experiments followed the coupled ice sheet–ocean experiments under the first phase of the Marine Ice Sheet–Ocean Model Intercomparison Project (MISOMIP1). A periodic pattern in the simulated mean basal melting rates is found to be highly consistent with the maximum barotropic stream function and also the grounding line retreat row by row,  which is likely to be related with the gyre break down near the grounding line caused by some non-physical instability events from the ocean bottom. Sensitivity tests are carried out, showing that this periodic pattern is not sensitive to the choice of couple time intervals and horizontal eddy viscosities but sensitive to vertical resolution in the ocean model, the chosen critical water column thickness in the wet-dry scheme, and the tracer properties for the nudging dry cells at the ice-ocean interface boundary. Further simulations are necessary to better explain the mechanism involved in the couple ice-ocean system, which is very significant for its application on the realistic ice-ocean systems in polar regions.</p>

Constraining ice shelf basalt melting rates from isochrone data

2021 ◽  
Author(s):  
Vjeran Visnjevic ◽  
Reinhard Drews ◽  
Clemens Schannwell ◽  
Inka Koch
Keyword(s):  
Ocean Circulation ◽  
Radar Data ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Ice Shelves ◽  
Inverse Approach ◽  
History Of ◽  
Forward And Inverse Modeling ◽  
Basal Melting

<p>Ice shelves buttress ice flow from the continent towards the ocean, and their disintegration results in increased ice discharge.  Ice-shelf evolution and integrity is influenced by surface accumulation, basal melting, and ice dynamics. We find signals of all of these processes imprinted in the ice-shelf stratigraphy that can be mapped using isochrones imaged with radar.</p><p>Our aim is to develop an inverse approach to infer ice shelf basal melt rates using radar isochrones as observational constraints. Here, we investigate the influence of basalt melt rates on the shape of isochrones using combined insights from both forward and inverse modeling. We use the 3D full Stokes model Elmer/Ice in our forward simulations, aiming to reproduce isochrone patterns observed in our data. Moreover we develop an inverse approach based on the shallow shelf approximating, aiming to constrain basal melt rates using isochronal radar data and surface velocities. Insights obtained from our simulations can also guide the collection of new radar data (e.g., profile lines along vs. across-flow) in a way that ambiguities in interpreting the ice-shelf stratigraphy can be minimized. Eventually, combining these approaches will enable us to better constrain the magnitude and history of basal melting, which will give valuable input for ocean circulation and sea level rise projections.</p>

scholarly journals The Effects of Basal Melting on the Present Flow of the Ross Ice Shelf, Antarctica

1986 ◽  
Vol 32 (110) ◽  
pp. 72-86 ◽  
Author(s):  
D.R. MacAyeal ◽  
R.H. Thomas
Keyword(s):  
Large Scale ◽  
Oceanic Circulation ◽  
Ice Shelf ◽  
Ice Streams ◽  
Ross Ice Shelf ◽  
Flow And Heat Transfer ◽  
Improve Model ◽  
Dependent Flow ◽  
Basal Melting ◽  
Shelf Flow

AbstractWe use a hybrid finite-element/finite-difference model of ice-shelf flow and heat transfer to investigate the effects of basal melting on the present observed flow of the Ross Ice Shelf, Two hypothetical basal melting scenarios are compared: (i) zero melting everywhere and (ii) melting sufficient to balance any large-scale patterns of ice-shelf thickening that would otherwise occur. As a result of the temperature-dependent flow law (which we idealize as having a constant activation energy of 120 kJ mol−1, a scaling coefficient of 1.3 N m−2s1/3, and an exponent of 3), simulated ice-shelf velocities for the second scenario are reduced by up to 20% below those of the first. Our results support the hypothesis that melting patterns presently maintain ice thickness in steady state and conform to patterns of oceanic circulation presently thought to ventilate the sub-ice cavity. Differences between the simulated and observed velocities are too large in the extreme south-eastern quarter of the ice shelf to permit verification of either basal melting scenario. These differences highlight the need to improve model boundary conditions at points where ice streams feed the ice shelf and where the ice shelf meets stagnant grounded ice.

scholarly journals The cavity under the Amery Ice Shelf, East Antarctica

2008 ◽  
Vol 54 (188) ◽  
pp. 881-887 ◽  
Author(s):  
B.K. Galton-Fenzi ◽  
C. Maraldi ◽  
R. Coleman ◽  
J. Hunter
Keyword(s):  
Water Column ◽  
Ocean Circulation ◽  
East Antarctica ◽  
Ocean Tide ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Ocean Tide Model ◽  
Amery Ice Shelf ◽  
Tidal Constituents

AbstractOcean circulation under ice shelves and associated rates of melting and freezing are strongly influenced by the shape of the sub-ice-shelf cavity. We have refined an existing method and used additional in situ measurements to estimate the cavity shape under the Amery Ice Shelf, East Antarctica. A finite-element hydrodynamic ocean-tide model was used to simulate the major tidal constituents for a range of different sub-Amery Ice Shelf cavity water-column thicknesses. The data are adjusted in the largely unsurveyed southern region of the ice-shelf cavity by comparing the complex error between simulated tides and in situ tides, derived from GPS observations. We show a significant improvement in the simulated tides, with a combined complex error of 1.8 cm, in comparison with past studies which show a complex error of ∼5.3 cm. Our bathymetry incorporates ice-draft data at the grounding line and seismic surveys, which have provided a considerable amount of new data. This technique has particular application when the water column beneath ice shelves is inaccessible and in situ GPS data are available.

scholarly journals Large flux of iron from the Amery Ice Shelf marine ice to Prydz Bay, East Antarctica

2016 ◽  
Vol 121 (8) ◽  
pp. 6009-6020 ◽  
Author(s):  
L. Herraiz-Borreguero ◽  
D. Lannuzel ◽  
P. van der Merwe ◽  
A. Treverrow ◽  
J. B. Pedro
Keyword(s):  
East Antarctica ◽  
Prydz Bay ◽  
Ice Shelf ◽  
Amery Ice Shelf
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