Marine Ecosystems Research Department - jamstec japan agency ...

Japan Marine Science and Technology Center
Frontier Research System for Global Change
Current at Layer 500m
Current at Layer 500m
250
>3cm/s
250
>3cm/s
0 10 20 cm/s
0 10 20 cm/s
200
200
150
150
100
100
50
50
50 100 150 200
50 100 150 200
Fig.28 The CIOM simulated 500-m (Atlantic Water Layer) circulation of March (left column) and September (right).
anomalies on the atmosphere is investigated with the
NCAR Community Climate Model (CCM, version
.). Model experiments are performed for the winter
and summer seasons with the greatest and least Arctic
ice coverage during the period -, when ice concentration
estimates were available from satellites.
Since there is strong natural climate variability at high
latitudes, we integrated -member ensembles of the
GCM to enhance the signal and reduce the model
"noise." The atmospheric response to the winter
extreme maximum (-) and minimum (-)
produces a local response to ice anomalies over the
subpolar seas of both the Atlantic and Pacific. The
response is robust and generally shallow with large
upward surface heat fluxes (> Wm-), near-surface
warming, enhanced precipitation, and below-normal
sea level pressure where sea ice receded, and the
reverse where the ice expanded. Additional information
about the winter simulations can be found in
Alexander et al. (). The atmospheric response to
reduced Arctic summer sea ice (based on summer of
) produces a local response to ice anomalies over
the Arctic seas. Observed composites based on
reduced sea ice in the Kara Sea display a structure
similar to the model response. This suggests that the
summer sea ice may force anomalies in the atmosphere.
The likely mechanism is diagnosed in the GCM
and additional details about the summer simulations
can be found in Bhatt et al. (). IARC has cooperated
with GFDL to produce a coupled ice-ocean
model consisting of the MOM. z-coordinate ocean
model coupled to the GFDL Sea Ice Simulator (SIS).
This coupled ice-ocean model is presently being
developed for use in studying the ocean climate system,
and for eventual coupling to land, atmosphere,
and ocean biogeochemical models. Of particular interest
to IARC is the study of low-frequency variability
of the Arctic climate system.
In general, the initiation of new fieldwork to establish
baseline information about the climate system or to
detect change of the system is an ineffective strategy.
This does not mean that we abandon observational
work. Indeed, it is our responsibility to maintain,
improve, and (in some cases) expand the basic observational
network. IARC/Frontier has identified a small
number of new field projects designed to significantly
contribute to our observationally based understanding
of the climate system. Scientists from AARI, ARM,
and IARC/Frontier are conducting a side-by-side test of
the older Russian radiometers and the modern ARM
instruments at the Barrow, Alaska. This -year program
is designed to identify biases and other discrepancies
147