Julienne Stroeve (PI)
University of Colorado Boulder
stroeve@kryos.colorado.edu

Diagnosing the Declining Arctic Sea Ice Cover: Applications and Analysis of the Next-generation Research Tools

We will contribute to modeling activities of the NASA GMAO and GISS through the evaluation and integrated application of CERES and MERRA products.  Our study focuses on the following research question: Why is the Arctic sea ice cover declining?  Climate models are in general agreement that the effects of greenhouse gas (GHG) loading will be seen first, and will be most pronounced, in the Arctic. Significant loss of sea ice is a common feature of these simulations.  In the past three summers, a multi-decadal trend of sea ice decline has been punctuated by extreme minima. Concurrently, the pack ice appears to be thinning, at least regionally. While part of the observed decline may represent the direct effects of GHG loading, there is abundant evidence of links with low frequency atmospheric variability that influence air, ocean, and sea ice circulation.  Interestingly, Antarctic sea ice has remained relatively unchanged over the same period.  Understanding the Arctic sea ice decline requires improved tools, including the CERES reprocessing effort based on the NASA GMAO GEOS-4 system and the upcoming MERRA effort, based on the advanced GEOS-5 system.  To address the problem of the declining Arctic sea ice cover, we will:   1) Conduct detailed assessments of variability and change in the atmospheric heat budget and surface energy fluxes over the Arctic Ocean as depicted in CERES, MERRA, ERA-40 and NCEP.  Comparative studies will contrast the Arctic with the much different behavior of the Antarctic sea ice system.  Application of the CERES and MERRA products requires extensive testing. Along with comparisons with the NCEP and ERA-40 re-analyses, we will evaluate individual budget terms and associated fields against observations, such as top of atmosphere radiation budgets from ERBE and ISCCP-D and surface heat fluxes from the SHEBA field program.  Working with the GMAO, we will assess how high-latitude treatments in the state-of-the-art MERRA system could be further improved and applied to next-generation systems, such as the Arctic System Reanalysis proposed as a U.S contribution to the International Polar Year.    2) Drive a state-of-the-art global ice-ocean model with output from CERES, MERRA, ERA-40 and NCEP, allowing us to investigate sea ice linkages in both hemispheres with changes in the atmospheric circulation and ocean heat budget in a rigorous, ensemble-based approach.    3) Conduct remote-sensing studies with an emphasis on providing an improved observational framework to diagnose the extreme Arctic sea ice minima of 2002-2004 in comparison to previous years (e.g. characteristics of melt onset and albedo, melt ponding, ice concentration, ice drift).    4) In conjunction with GISS, apply results from the above investigations to assess the veracity of sea ice processes in MERRA and CERES and as simulated in a suite of coupled global climate models, with the goal of improving simulations of the present and future states of the Arctic and Antarctic.

+ Back to Participant Listing