Geoscience Reference
In-Depth Information
Figure 2.3.
Bathymetry of the Arctic Ocean and major geographical features (adapted
from Clark and Grantz,
2002
, by permission of AGU).
(hereafter termed “the Atlantic sector”) by relatively warm ocean waters that dis-
courage ice formation.
The sea ice cover is not a featureless slab, but consists of individual ice floes rang-
ing from a few meters to many kilometers across. Floes are separated by roughly lin-
ear openings, known as leads, and irregularly shaped openings known as polynyas.
Typical winter ice concentrations over the central Arctic Ocean are 98-99 percent,
compared to 85-95 percent during late summer. During winter, leads generally
quickly refreeze to form areas of new, thin ice. Ice concentrations decrease near
the sea ice/open ocean margins.
Figure 2.5
shows a typical summer sea ice field
over the central Arctic Ocean based on MODIS satellite imagery.
Figure 2.6
shows
another summer scene that captures the transition from sea ice to open ocean waters
(termed “the marginal ice zone”). Note how the sea ice margin ranges from rather
sharp to very diffuse. The image clearly shows numerous large individual floes, as
well as polynyas.
Apart from areas of landfast ice along coasts (ice locked to the shoreline), the sea
ice cover is almost constantly in motion. This is because of the influence of wind
