Projected Impact of Climate Change on the Energy Budget of
the Arctic Ocean
by a Global Climate Model
James R. Miller and Gary L. Russell
2002: Journal of Climate, 15, 3028-3042
Abstract
The annual energy budget of the Arctic Ocean is characterized by
a net heat loss at the air-sea interface that is balanced by oceanic
heat transport into the Arctic. Two 150-year simulations (1950-2099)
of a global climate model are used to examine how this balance might
change if atmospheric greenhouse gases (GHGs) increase. One is a
control simulation for the present climate with constant 1950
atmospheric composition, and the other is a transient experiment with
observed GHGs from 1950 to 1990 and 0.5% annual compounded increases of
CO2 after 1990. For the present climate the model agrees well with
observations of radiative fluxes at the top of the atmosphere,
atmospheric advective energy transport into the Arctic, and surface air
temperature. It also simulates the seasonal cycle and summer increase
of cloud cover and the seasonal cycle of sea-ice cover. In addition,
the changes in high-latitude surface air temperature and sea-ice cover
in the GHG experiment are consistent with observed changes during the
last 40 and 20 years, respectively.
Relative to the control, the last 50-year period of the GHG
experiment indicates that even though the net annual incident solar
radiation at the surface decreases by 4.6 W/mē (because of greater
cloud cover and increased cloud optical depth), the absorbed solar
radiation increases by 2.8 W/mē (because of less sea ice). Increased
cloud cover and warmer air also cause increased downward thermal
radiation at the surface so that the net radiation into the ocean
increases by 5.0 W/mē. The annual increase in radiation into the
ocean, however, is compensated by larger increases in sensible and
latent heat fluxes out of the ocean. Although the net energy loss from
the ocean surface increases by 0.8 W/mē, this is less than the
interannual variability, and the increase may not indicate a long-term
trend.
The seasonal cycle of heat fluxes is significantly enhanced. The
downward surface heat flux increases in summer (maximum of 19 W/mē or
23% in June) while the upward heat flux increases in winter (maximum of
16 W/mē or 28% in November). The increased downward flux in summer is
due to a combination of increases in absorbed solar and thermal
radiation and smaller losses of sensible and latent heat. The
increased heat loss in winter is due to increased sensible and latent
heat fluxes, which in turn are due to reduced sea-ice cover. On the
other hand, the seasonal cycle of surface air temperature is damped, as
there is a large increase in winter temperature but little change in
summer. The changes that occur in the various quantities exhibit
spatial variability, with the changes being generally larger in coastal
areas at the ice margins than in the central Arctic.
[
Download PDF ]