Abstract

Abstract. Coupled ice sheet–ocean models capable of simulating moving grounding lines are just becoming available. Such models have a broad range of potential applications in studying the dynamics of marine ice sheets and tidewater glaciers, from process studies to future projections of ice mass loss and sea level rise. The Marine Ice Sheet–Ocean Model Intercomparison Project (MISOMIP) is a community effort aimed at designing and coordinating a series of model intercomparison projects (MIPs) for model evaluation in idealized setups, model verification based on observations, and future projections for key regions of the West Antarctic Ice Sheet (WAIS). Here we describe computational experiments constituting three interrelated MIPs for marine ice sheet models and regional ocean circulation models incorporating ice shelf cavities. These consist of ice sheet experiments under the Marine Ice Sheet MIP third phase (MISMIP+), ocean experiments under the Ice Shelf-Ocean MIP second phase (ISOMIP+) and coupled ice sheet–ocean experiments under the MISOMIP first phase (MISOMIP1). All three MIPs use a shared domain with idealized bedrock topography and forcing, allowing the coupled simulations (MISOMIP1) to be compared directly to the individual component simulations (MISMIP+ and ISOMIP+). The experiments, which have qualitative similarities to Pine Island Glacier Ice Shelf and the adjacent region of the Amundsen Sea, are designed to explore the effects of changes in ocean conditions, specifically the temperature at depth, on basal melting and ice dynamics. In future work, differences between model results will form the basis for the evaluation of the participating models.

Highlights

  • The Marine Ice Sheet–Ocean Model Intercomparison Project (MISOMIP) is a targeted activity of the World Climate Research Programme’s Climate and Cryosphere (CliC) project

  • MISOMIP1 differs from this previous work in having (1) steeper channel walls, meaning a stronger change in buttressing as the ice-shelf thickness changes, (2) a larger region of open ocean allowing for ocean dynamics both inside and outside the cavity, and (3) a bedrock topography with an upward-sloping region in the ice-flow direction, allowing us to investigate the possibility that thinning or other changes in the state of the ice sheet could trigger marine icesheet instability (MISI; e.g., Weertman, 1974)

  • The COLD potential temperature profile is constant at the surface freezing temperature throughout the water column and has a lower salinity, resulting in WARM and COLD density profiles that are nearly identical throughout the water column, reducing convective instabilities resulting from the transitions between COLD and WARM conditions that occur in Ocean1–2 as well as the MISOMIP1 IceOcean1–2 experiments

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Summary

Introduction

The Marine Ice Sheet–Ocean Model Intercomparison Project (MISOMIP) is a targeted activity of the World Climate Research Programme’s Climate and Cryosphere (CliC) project. Results from 16 models with a total of 33 unique configurations showed that initial steady states as well as the reversibility of the dynamics differed significantly depending on the stress approximation and horizontal resolution Both MISMIP and MISMIP3d provided a basis for a number of follow-up studies focused on both improvements in numerical methods (e.g., Drouet et al, 2013; Leguy et al, 2014; Feldmann et al, 2014; Seroussi et al, 2014b) and exploring changes in the model topography and physics parameterizations (e.g., Leguy et al, 2014; Feldmann and Levermann, 2015; Tsai et al, 2015). These factors are likely to lead a larger number of ISOMIP+ participants and formal publication of the analysis, both of which were lacking in ISOMIP

Coupled ice sheet–ocean modeling
Goals of the three new MIPs
Experimental setup
Experiments
Requested output
Shared setup across the five experiments
Domain and topography
Calving
Forcing
Boundary and initial conditions
COM grid resolution
COM mixing parameterizations
COM equation of state
COM melt parameterization
Ocean0: warm initial conditions and forcing with static ice-shelf topography
MISOMIP1 design
IceOcean1: retreat and re-advance without dynamic calving
Component resolutions and parameterizations
Conclusions
Findings
Code and data availability
Full Text
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