Thomas Haine (PI)
Johns Hopkins University
thomas.haine@jhu.edu

Space-Based Estimates of Arctic/Sub-Arctic Exchange Using Data Assimilation and Ocean Models

Recent studies show that interannual fluctuations in North Atlantic climate have significant influence on transfer of freshwater and heat into the Arctic Ocean.  In turn, the strength of the dense overflows returning south across the Greenland-Scotland Ridge are modulated by this variability, lagged with a delay of a few years. Other studies raise the possibility of substantial weakening and/or freshening of the overflows, and hence the meridional-overturning circulation, in response to anthropogenic-induced climate change.  A particularly urgent case therefore exists to study air/sea/ice interactions in the subpolar Atlantic and Greenland/Iceland/Norwegian Seas.

To address this issue we propose a project to develop, test, and apply a prototype model/data assimilation system that can synthesize remote-sensed and in-situ observations to estimate climate-critical fluxes across Denmark Strait. We seek to answer the question: What is the benefit of assimilation to estimate this exchange, what is the current state, and where are the greatest uncertainties?

The approach will be to develop a hierarchy of regional models of the Denmark Strait and Irminger Sea with horizontal resolution between 1/12 and 1/60 deg. In tandem, we will develop a variational data assimilation capability that synthesizes remotely-sensed observations of sea-surface height, sea-surface temperature, sea-surface salinity, wind stress, and sea ice with the circulation models. Using twin experiments to test the system, we will determine the prospects for estimating mass, heat, freshwater exchange across the Denmark Strait and water-mass conversion in the Irminger Sea overflow. We will then apply the model/data assimilation system using satellite and in-situ data during select summer periods of 2003 and 2004 to formally estimate the oceanic state in the Denmark Strait at those times. The result will be an optimal blend of remote-sensed data, in-situ data, and dynamical constraints that will be of great value to researchers studying processes and climate variability near Denmark Strait. Other project outcomes include: a quantitative assessment of the relative merits of each part of the observing network in this area, guidance for climate modelers on systematic errors in their climate forecast models, and improved practical knowledge of accurate ocean data assimilation in very high resolution regional models.

The project will be a collaborative effort between 2 groups at Johns Hopkins University: The Department of Earth and Planetary Sciences and the Ocean Remote Sensing Group of the Applied Physics Laboratory.

+ Back to Participant Listing