First results from coupling the Parallel Ice Sheet Model with the Modular Ocean Model via an Antarctic ice-shelf cavity module

2021 ◽  
Author(s):  
Moritz Kreuzer ◽  
Ronja Reese ◽  
Willem Huiskamp ◽  
Stefan Petri ◽  
Torsten Albrecht ◽  
...  
Keyword(s):  
Time Scales ◽  
General Circulation ◽  
Ice Sheet ◽  
Circulation Model ◽  
Ocean Model ◽  
Global Ocean ◽  
Ice Shelf ◽  
Antarctic Ice Sheet ◽  
First Results ◽  
The Antarctic

<p>The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high resolution configurations, limiting these studies to individual glaciers or regions over short time scales of decades to a few centuries. To study global and long term interactions, we developed a framework to couple the dynamic ice sheet model PISM with the global ocean general circulation model MOM5 via the ice-shelf cavity module PICO. Since ice-shelf cavities are not resolved by MOM5, but parameterized with the box model PICO, the framework allows the ice sheet and ocean model to be run at resolution of 16 km and 3 degrees, respectively. We present first results from our coupled setup and discuss stability, feedbacks, and interactions of the Antarctic Ice Sheet and the global ocean system on millennial time scales.</p>

scholarly journals Coupling framework (1.0) for the ice sheet model PISM (1.1.1) and the ocean model MOM5 (5.1.0) via the ice-shelf cavity module PICO

2020 ◽  
Author(s):  
Moritz Kreuzer ◽  
Ronja Reese ◽  
Willem Nicholas Huiskamp ◽  
Stefan Petri ◽  
Torsten Albrecht ◽  
...  
Keyword(s):  
Time Scales ◽  
General Circulation ◽  
Ice Sheet ◽  
Circulation Model ◽  
Ocean Model ◽  
Global Ocean ◽  
Energy Fluxes ◽  
Ice Shelf ◽  
Antarctic Ice Sheet ◽  
Wide Range

Abstract. The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high resolution configurations, limiting these studies to individual glaciers or regions over short time scales of decades to a few centuries. We present a framework to couple the dynamic ice sheet model PISM with the global ocean general circulation model MOM5 via the ice-shelf cavity module PICO. Since ice-shelf cavities are not resolved by MOM5, but parameterized with the box model PICO, the framework allows the ice sheet and ocean model to be run at resolution of 16 km and 3 degree, respectively. This approach makes the coupled configuration a useful tool for the analysis of interactions between the entire Antarctic Ice Sheet and the Earth system over time spans on the order of centuries to millennia. In this study we describe the technical implementation of this coupling framework: sub-shelf melting in the ice sheet model is calculated by PICO from modeled ocean temperatures and salinities at the depth of the continental shelf and, vice versa, the resulting mass and energy fluxes from the melting at the ice-ocean interface are transferred to the ocean model. Mass and energy fluxes are shown to be conserved to machine precision across the considered model domains. The implementation is computationally efficient as it introduces only minimal overhead. The framework deals with heterogeneous spatial grid geometries, varying grid resolutions and time scales between the ice and ocean model in a generic way, and can thus be adopted to a wide range of model setups.

scholarly journals Coupling framework (1.0) for the PISM (1.1.4) ice sheet model and the MOM5 (5.1.0) ocean model via the PICO ice shelf cavity model in an Antarctic domain

2021 ◽  
Vol 14 (6) ◽  
pp. 3697-3714
Author(s):  
Moritz Kreuzer ◽  
Ronja Reese ◽  
Willem Nicholas Huiskamp ◽  
Stefan Petri ◽  
Torsten Albrecht ◽  
...  
Keyword(s):  
General Circulation ◽  
Ice Sheet ◽  
Ocean Model ◽  
Global Ocean ◽  
Cavity Model ◽  
Energy Fluxes ◽  
Ice Shelf ◽  
Antarctic Ice Sheet ◽  
Wide Range ◽  
The Antarctic

Abstract. The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high-resolution configurations, limiting these studies to individual glaciers or regions over short timescales of decades to a few centuries. We present a framework to couple the dynamic ice sheet model PISM (Parallel Ice Sheet Model) with the global ocean general circulation model MOM5 (Modular Ocean Model) via the ice shelf cavity model PICO (Potsdam Ice-shelf Cavity mOdel). As ice shelf cavities are not resolved by MOM5 but are parameterized with the PICO box model, the framework allows the ice sheet and ocean components to be run at resolutions of 16 km and 3∘ respectively. This approach makes the coupled configuration a useful tool for the analysis of interactions between the Antarctic Ice Sheet and the global ocean over time spans of the order of centuries to millennia. In this study, we describe the technical implementation of this coupling framework: sub-shelf melting in the ice sheet component is calculated by PICO from modelled ocean temperatures and salinities at the depth of the continental shelf, and, vice versa, the resulting mass and energy fluxes from melting at the ice–ocean interface are transferred to the ocean component. Mass and energy fluxes are shown to be conserved to machine precision across the considered component domains. The implementation is computationally efficient as it introduces only minimal overhead. Furthermore, the coupled model is evaluated in a 4000 year simulation under constant present-day climate forcing and is found to be stable with respect to the ocean and ice sheet spin-up states. The framework deals with heterogeneous spatial grid geometries, varying grid resolutions, and timescales between the ice and ocean component in a generic way; thus, it can be adopted to a wide range of model set-ups.

Coupling the Parallel Ice Sheet Model with the Modular Ocean Model via an Antarctic ice-shelf cavity module

2020 ◽  
Author(s):  
Moritz Kreuzer ◽  
Ronja Reese ◽  
Willem Huiskamp ◽  
Stefan Petri ◽  
Ricarda Winkelmann
Keyword(s):  
Time Scales ◽  
Ice Sheet ◽  
Mass Conservation ◽  
Ocean Model ◽  
Computationally Efficient ◽  
Ice Shelf ◽  
Current Mass ◽  
Modular Ocean Model ◽  
Interactive Modelling ◽  
The Antarctic

<p>Ocean-ice shelf interactions are the main drivers for the current mass loss from the Antarctic Ice Sheet. Recent studies have shown that increased continental meltwater input can enhance discharge through ice-ocean feedbacks. This raises the need for interactive modelling between ocean and ice-sheet systems to assess the consequences of additional freshwater input on the Antarctic region and beyond. While high-resolution simulations (1/4 degree or greater) can resolve detailed interactions between the ocean and ice shelf, the computational costs make them applicable only for regional studies or decadal to centennial time scales. In this study we present a framework for coupling a coarse resolution ocean model (MOM) to the Parallel Ice Sheet Model (PISM) via the Potsdam Ice-shelf Cavity mOdel (PICO). The intermediate model PICO approximates the overturning circulation in ice shelf cavities and includes ice-ocean boundary layer physics. We present this offline coupling approach and discuss the fluxes exchanged between the distinct model runs as well as energy and mass conservation. Using this flexible and computationally efficient framework, feedbacks between the ice and ocean can be analysed on a global spatial scale and paleoclimate time-scales.</p><p> </p>

scholarly journals Competing influences of the ocean, atmosphere and solid earth on transient Miocene Antarctic ice sheet variability

2021 ◽  
Author(s):  
Lennert Bastiaan Stap ◽  
Constantijn J. Berends ◽  
Meike D. W. Scherrenberg ◽  
Roderik S. W. van de Wal ◽  
Edward G. W. Gasson
Keyword(s):  
General Circulation ◽  
Ice Sheet ◽  
Circulation Model ◽  
Climate Forcing ◽  
Ice Shelf ◽  
Antarctic Ice Sheet ◽  
Ice Volume ◽  
Bedrock Topography ◽  
Co2 Levels ◽  
Transient Simulations

Abstract. Benthic δ18O levels vary strongly during the warmer-than-modern early- and mid-Miocene (23 to 14 Myr ago), suggesting a dynamic Antarctic ice sheet (AIS). So far, however, realistic simulations of the Miocene AIS have been limited to equilibrium states under different CO2 levels and orbital settings. Earlier transient simulations lacked ice-sheet-atmosphere interactions, and used a present-day rather than Miocene Antarctic bedrock topography. Here, we quantify the effect of ice-sheet-atmosphere interactions, running IMAU-ICE using climate forcing from Miocene simulations by the general circulation model GENESIS. Utilising a recently developed matrix interpolation method enables us to interpolate the climate forcing based on CO2 levels (between 280 and 840 ppm) as well as ice sheet configurations (between no ice and a large ice sheet). We furthermore implement recent reconstructions of Miocene Antarctic bedrock topography. We find that the positive albedo-temperature feedback, partly compensated by the negative ice-volume-precipitation feedback, increases hysteresis in the relation between CO2 and ice volume (V). Together, these ice-sheet-atmosphere interactions decrease the amplitude of AIS variability caused by 40-kyr forcing CO2 cycles by 21 % in transient simulations. Thereby, they also diminish the contribution of AIS variability to benthic δ18O fluctuations. Furthermore, we show that under equal atmospheric and oceanic forcing, the amplitude of 40-kyr transient AIS variability becomes 10 % smaller during the early- and mid-Miocene, due to the evolving bedrock topography. Lastly, we quantify the influence of ice shelf formation around the Antarctic margins, by comparing simulations with Last Glacial Maximum (LGM) basal melt conditions, to ones in which ice shelf growth is prevented. Ice shelf formation increases hysteresis in the CO2-V relation, and amplifies 40-kyr AIS variability by 19 % using LGM basal melt rates, and by 5 % in our reference setting.

Evaluation of Interior Circulation in a High-Resolution Global Ocean Model. Part I: Deep and Bottom Waters

2004 ◽  
Vol 34 (12) ◽  
pp. 2592-2614 ◽  
Author(s):  
Alexander Sen Gupta ◽  
Matthew H. England
Keyword(s):  
Time Scales ◽  
Mixed Layer ◽  
Deep Water ◽  
General Circulation ◽  
Bottom Water ◽  
Circulation Model ◽  
Global Ocean ◽  
Western Boundary ◽  
Model Skill ◽  
The Antarctic

Abstract Global watermass ventilation pathways and time scales are investigated using an “eddy permitting” (¼°) offline tracer model. Unlike previous Lagrangian trajectory studies, here an offline model based on a complete tracer equation that includes three-dimensional advection and mixing is employed. In doing so, the authors are able to meaningfully simulate chlorofluorocarbon (CFC) uptake and assess model skill against observation. This is the first time an eddy-permitting model has been subjected to such an assessment of interior ocean ventilation. The offline model is forced by seasonally varying prescribed velocity, temperature, and salinity fields of a state-of-the-art ocean general circulation model. A seasonally varying mixed layer parameterization is incorporated to account for the degradation of surface convection processes resulting from the temporal averaging. A series of CFC simulations are assessed against observations to investigate interdecadal-time-scale ventilation using a variety of mixed layer criteria. Simulated tracer inventories and penetration depths are in good agreement with observations, especially for thermocline, mode, and surface waters. Deep water from the Labrador Sea is well represented, forming a distinct deep western boundary current that branches at the equator, although concentrations are lower than observed. The formation of bottom water, which occurs around the Antarctic margin, is also generally too weak, although there is excellent qualitative agreement with observations in the region of the Ross and Weddell Seas. Multicentury ventilation of the outflow of North Atlantic Deep Water and bottom water from the Antarctic Margin are investigated using 1000-yr passive tracer experiments with specified interior source regions. The model captures many of the detailed pathways evident from observations, with much of the discrepancy accounted for by differences between actual and modeled topography. A comparison between model-derived “tracer age” and Δ14C “advection age” provides a semiquantitative assessment of model skill at these longer time scales.

Comparison of peri-Antarctic sub-shelf melt rates in coupled and uncoupled ice-sheet model simulations

2020 ◽  
Author(s):  
Lars Zipf ◽  
Charles Pelletier ◽  
Konstanze Haubner ◽  
Sainan Sun ◽  
Hugues Goosse ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Ice Sheet ◽  
Optimal Solution ◽  
Ocean Model ◽  
Model Framework ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
First Results ◽  
Framework Conditions ◽  
The Antarctic

<p>Sub-shelf melting is the main driver of the mass loss of the Antarctic ice sheet. Various parametrizations exist to estimate basal melt rates within standalone ice sheet models, but they are not able to capture complex ocean circulation. Therefore, high resolution coupled ice sheet-ocean models are the ultimate approach to simulate observed sub-shelf melt rates on short time scales and thereby improve projections of future Antarctic sea level contribution.</p><p>Here, we present first results of a hindcast (last 30 years) of the new circumpolar coupled Southern Ocean – Antarctic ice sheet configuration, developed within the framework of the PARAMOUR project. The configuration, which captures whole Antarctica, is based on the ocean and sea ice model NEMO3.6-LIM3, providing the ice sheet model with monthly sub-shelf melt rates, and the Antarctic ice sheet model f.ETISh v1.5, providing the updated ice shelf cavity geometry to the ocean model. Different difficulties are tackled for the coupling: The initialisation of the ice sheet model is optimised for the chosen resolution of 8km, which is a tradeoff between capturing the main features for the peri-Antarctic setup and respecting the model purpose as fast ice sheet model. Framework conditions for the coupling, e.g. a constant ice-ocean mask, are tested and implemented. The optimal solution to estimate sub-shelf melt for small ice shelves that are not resolved in the ocean model due to the different resolution of the ice sheet and the ocean model, is investigated.<br>Sub-shelf melt rates of the coupled setup are compared to those modeled by the standalone ocean model and those of the standalone ice sheet model with different sub-shelf melt rate parametrizations (ISMIP6, plume, PICO, PICOP) and the sensitivity of the response of the ice sheet for the different basal melt rate patterns are investigated.</p>

scholarly journals Modelling the Antarctic ice-sheet changes through time

1994 ◽  
Vol 20 ◽  
pp. 291-297 ◽  
Author(s):  
W.F. Budd ◽  
D. Jenssen ◽  
B. Coutts
Keyword(s):  
Sea Level ◽  
General Circulation ◽  
Ice Sheet ◽  
Circulation Model ◽  
Glacial Cycle ◽  
Climatic Forcing ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
Future Global Warming ◽  
The Antarctic

A new assessment is made of the possible range of responses of the Antarctic ice sheet to future global warming by performing a series of sensitivity tests to prescribed climatic forcing with an ice-sheet model. The model includes thermodynamics; it is three-dimensional, with 20 km horizontal grid spacing and 30 points in the vertical, and it treats the ice shelves explicitly. To obtain an appropriate initial present state for the ice sheet, it has been necessary to perform a series of simulations through the last glacial cycle with prescribed forcing including accumulation, sea level are less importantly climatic temperature. For the future climatic forcing, General Circulation Model simulations have been used with particular concern for the changes in the sea-ice cover and ocean warming. Effects of progressive changes have been examined with increases of basal-melt rates up to 10 m a1, surface annual mean temperatures by up to 7°C and surface-accumulation rates to double the present values. Without additional accumulation, the increased basal melt of 10 m a-1would greatly reduce the ice shelves and contribute to sea-level rise of 0.3 m in 100 years and over 0.6 m by 500 years. The additional accumulation counteracts this to dive about zero change by 100 years and -1.2 m by 500 years.

scholarly journals Ice sheet response to sub-shelf melt rates in coupled and uncoupled peri-Antarctic ice-sheet model simulations

2021 ◽  
Author(s):  
Lars Zipf ◽  
Charles Pelletier ◽  
Konstanze Haubner ◽  
Sainan Sun ◽  
Frank Pattyn
Keyword(s):  
Ocean Circulation ◽  
Ice Sheet ◽  
Ocean Model ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Antarctic Ice Sheet ◽  
Main Driver ◽  
First Results ◽  
The Impact ◽  
Ice Model

<p>Sub-shelf melting is the main driver of Antarctica's ice sheet mass loss. However, sub-shelf melt rate parameterizations for standalone ice models lack the capability to capture complex ocean circulation within ice shelf cavities. To overcome drawbacks of standalone models and to improve melt parameterizations, high resolution coupling of ice sheet and ocean models are capable of hindcasting past decennia and be compared to observations.</p><p>Here, we present first results of a hindcast (1985-2018) of the new circumpolar coupled Southern Ocean – Antarctic ice sheet configuration, developed within the framework of the PARAMOUR project. The configuration is based on the ocean and sea ice model NEMO3.6-LIM3 and the ice sheet model f.ETISh v1.7. The coupling routine facilitates exchange of monthly sub-shelf melt rates (from ocean to ice model) and evolving ice shelf cavity geometry (from ice to ocean model).</p><p>We investigate the impact of the coupling frequency (more precisely, the frequency of updating the ice shelf cavity geometry within the ocean model) on the sub-shelf melt rates and its feedback on the ice dynamics. We further compare the sub-shelf melt rates of the coupled setup to those of the standalone ice sheet model with different sub-shelf melt rate parametrizations (ISMIP6, plume, PICO, PICOP) and investigate the sensitivity of the response of the ice sheet for the different basal melt rate patterns on decadal time scales.</p>

scholarly journals Effect of meltwater input from the Antarctic ice sheet on the thermohaline circulation

1998 ◽  
Vol 27 ◽  
pp. 311-315 ◽  
Author(s):  
Uwf Mikolajewicz
Keyword(s):  
Southern Ocean ◽  
North Atlantic ◽  
General Circulation ◽  
Thermohaline Circulation ◽  
Ice Sheet ◽  
Circulation Model ◽  
Balance Model ◽  
Surface Cooling ◽  
Antarctic Ice Sheet ◽  
The Antarctic

The potential effect of meltwater input from the Antarctic ice sheet is studied in sensitivity experiments with an ocean general circulation model coupled to an energy-balance model of the atmosphere. The effect is generally a reduction of surface salinity and deep convection in The Southern Ocean, associated with surface cooling. There is an accompanying, delayed intensification of the overturning in the Northern Hemisphere, leading to warmer conditions over both the North Atlantic and North Pacific With a sufficiently large meltwater pulse it is possible to trigger switches between different steady states of the ocean's thermohaline circulation, which differ mainly in the formation rates of North Atlantic Deep Water. Thus a transient perturbation in the Southern Ocean can lead to long-term climate changes in both hemispheres. The model reacts morè sensitively to melt water input into theWeddell Sea than into the Ross Sea.

scholarly journals Modelling the Antarctic ice-sheet changes through time

1994 ◽  
Vol 20 ◽  
pp. 291-297 ◽  
Author(s):  
W.F. Budd ◽  
D. Jenssen ◽  
B. Coutts
Keyword(s):  
Sea Level ◽  
General Circulation ◽  
Ice Sheet ◽  
Circulation Model ◽  
Glacial Cycle ◽  
Climatic Forcing ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
Future Global Warming ◽  
The Antarctic

A new assessment is made of the possible range of responses of the Antarctic ice sheet to future global warming by performing a series of sensitivity tests to prescribed climatic forcing with an ice-sheet model. The model includes thermodynamics; it is three-dimensional, with 20 km horizontal grid spacing and 30 points in the vertical, and it treats the ice shelves explicitly. To obtain an appropriate initial present state for the ice sheet, it has been necessary to perform a series of simulations through the last glacial cycle with prescribed forcing including accumulation, sea level are less importantly climatic temperature. For the future climatic forcing, General Circulation Model simulations have been used with particular concern for the changes in the sea-ice cover and ocean warming. Effects of progressive changes have been examined with increases of basal-melt rates up to 10 m a1, surface annual mean temperatures by up to 7°C and surface-accumulation rates to double the present values. Without additional accumulation, the increased basal melt of 10 m a-1 would greatly reduce the ice shelves and contribute to sea-level rise of 0.3 m in 100 years and over 0.6 m by 500 years. The additional accumulation counteracts this to dive about zero change by 100 years and -1.2 m by 500 years.

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