Coupling ice-shelf basal melt rates in the Energy Exascale Earth System (E3SM) Model

Tuesday, December 10, 2019 - 08:00
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Freshwater flux from the Antarctic Ice Sheet (AIS), which predominantly occurs through ice shelf basal melting and iceberg calving, is one of the largest sources of uncertainty regarding sea-level rise in a changing climate. Yet these processes are generally poorly represented in current Earth System Models (ESMs). As a step towards full ice sheet coupling in an ESM, the new Department of Energy’s Energy Exascale Earth System Model (E3SM) has the capability to simulate ocean circulation under static ice shelf cavities, which can then be used to calculate ice shelf basal melt rates. We have also implemented a data iceberg forcing capability, allowing us to represent the other dominant mass loss process from the AIS. Here we present results from global simulations using these capabilities, in both fully-coupled and partially-coupled (active ocean/sea-ice with atmospheric forcing) configurations. We find that in the early part of the simulations, we are able to produce ice shelf basal melt rates in line with present-day observations. However as the simulations progress, some ice shelves experience a transition to extremely high melt rates, which then have global climate implications. A detailed study of the mechanisms in the model that trigger this instability is the subject of a companion presentation, “Potential for tipping point in melting beneath Filchner-Ronne Ice Shelf triggered by melt from neighboring ice shelves”.

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