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A regionally coupled atmosphere-ocean and sea ice model of the Arctic
Ksenia Glushak, Dmitry Sein and Uwe Mikolajewicz
Max-Planck Institute for Meteorology, Bundesstrasse 53, 20146 Hamburg. Germany; ksenia.glushak@zmaw.de
1. Introduction
To correctly understand the latest changes with decline
Arctic sea ice, as well as the changes on decadal and
interannual scale, it is necessary to consider the dynamics of
atmosphere, ocean and sea ice. The atmosphere, as well as
the ocean shows significant decadal and interannual changes
in this remote region. Unfortunately, global coupled climate
models do not have sufficient resolution to represent key
processes in this area. A regional climate model in this case
may show a better result, due to increased horizontal
resolution and the more flexible model setup.
2. Model description
To simulate the climate of the last decades the regional
atmospheric model REMO coupled to the global ocean
model MPIOM was used. REMO was used in different
versions. It has 27 vertical levels and horizontal resolutions
of 1º or 0.5º. The ocean model was configured in such a way
that one pole of the bipolar grid was located over western
Canada and the over one over southern Russia. This setup
results in horizontal resolution of 10 to 15 km over the
Arctic basin (see e.g. Fig. 1). The individual models were
coupled using the Oasis coupler.
Figure 1. Grid setup. Red border is the REMO area.
Beside the difference in the horizontal resolutions, different
forcing was used to drive the REMO model. NCEP-NCAR
and ERA40 re-analysis covered almost the same time slices,
except that NCEP-NCAR is started ten years early than
ERA40 in 1948, and continue after August 2002. Our
knowledge about the climate of the Arctic region suffers
from lack of the observations within the central Arctic basin,
especially before the “satellite era”, which started in 1979.
The difference between the two reanalysis is bigger in this
time period, and it is important to drive the model with both
reanalysis to understand how sensitive the model to the
choice of the driving forcing.
To validate the model different reanalysis were used as well
as observations data. Unfortunately, back in time over the
central basin the observation data had a big gaps, and some
of the fields like total cloud cover are very hard to evaluate
on the decadal scale.
Currently we are testing the model in the coarser resolution
version. Preliminary results indicate a good reproduction of
the observed climatology (see e.g. Fig. 2). After availability
of the new next generation super computer HLRE II at
DKRZ (Deutsches Klimarechenzentrum), which is
scheduled for the next weeks, we will perform a set of
simulations with different model setups. The results will be
presented on the poster.
Figure 2. Sea ice concentration from the model
simulations (top) and from satellite data (NSIDC,
bottom). Mean February (left) and July (right)
values calculated over 1980-1990.
As next step we will couple the land hydrology. The set up
of the atmospheric model has been chosen to include the
catchment of all rivers ending in the Arctic Ocean. With this
model we will study the water cycle of the Arctic, and its
variations.