Glaciers within the Amundsen Sea Embayment (ASE) are rapidly retreating and so contributing »10% of current global sea level rise, primarily through basal melting. Here the focus is atmospheric features that influence the mass balance of these glaciers and their representation in atmospheric models. New radiosondes and surface-based observations show that global reanalysis products contain relatively large biases in the vicinity of Pine Island Glacier (PIG), e.g. near-surface temperatures 1.8 ±C (ERA-I) to 6.8 ±C (MERRA) lower than observed. The reanalyses all underestimate wind speed during orographically-forced strong wind events and struggle to reproduce low-level jets. These biases would contribute to errors in surface heat fluxes and thus the simulated supply of ocean heat leading to PIG melting. Ten new ice cores show that there is no significant trend in accumulation on PIG between 1979 and 2013. RACMO2.3 and four global reanalysis products broadly reproduce the observed time series and the lack of any significant trend. The zonal pressure gradient between the Amundsen Sea and the Antarctic Peninsula is the main driver of variability in accumulation on PIG. Finally, the meteorological conditions associated with high heat flux events within coastal polynyas in the ASE are investigated. In three case studies high resolution simulations produce turbulent heat fluxes that are 10-20% (up to 100 W m¡2) larger than those in coarse resolution simulations. Representation of a hydraulic jump at the base of a slope is the key driver of the increased heat fluxes in a polynya close to PIG, with its presence leading to large differences in surface fluxes in the simulations. Overall it is shown that moving towards using higher resolution atmospheric products will both reduce the magnitude of coastal biases near PIG in reanalysis products, and allow complex orographic flows, important to coastal polynya processes, to be more adequately resolved.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:743356 |
| Date | January 2018 |
| Creators | Jones, Richard Wilson |
| Publisher | University of East Anglia |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ueaeprints.uea.ac.uk/66998/ |
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