1994 Arctic Ocean Section
ture section from the
Chukchi shelf (left)
to the Eurasian
flank of the Lomono-
sov Ridge (right).
The warm cores
appear at approxi-
mately 200400 db
above each primary
The station numbers
are across the top
of the figure.
Chukchi shelf to the North Pole. We observed multiple warm cores in the
Atlantic layer (depths of about 200400 m) near 1.0C along the Chukchi
boundary and warmer than 1.5C on the Eurasian side of the Lomonosov Ridge.
Earlier data from the Makarov Basin showed no water in this layer warmer
than 0.5C. In 1993 the Institute of Oceanographic Sciences (Patricia Bay)
group found water warmer than 1C on the Makarov slope just north of the
Chukchi Sea. The AOS-94 data extend this finding, showing the Atlantic
layer near both the Chukchi and Lomonosov ridge boundary areas to be 0.5C
warmer than measured before 1993. In some places the insulating fresh, cold
upper layer was somewhat eroded, though far from completely. One of the
important issues facing us now is to place this warming in context. Such sub-
decadal variability is important to climate models.
We found the central Canadian sector of the Arctic Ocean to be an ocean-
ographically active environment, not a "dead end" isolated from any active
role in the global circulation by the shallow sill through the Bering Strait, the
Lomonosov and other ridges, and its sheer distance from the North Atlantic
Ocean. Instead, the Canadian sector is importing water, modifying it and
exporting it in ways that have important effects and consequences.
For example, biological activity on the Chukchi shelf is so high in summer that
phytoplankton photosynthesis can supersaturate oxygen in the surface waters there
by almost 50% in places, yet the debris left behind by those organisms and their
predators sinks and decays, regenerating nutrients and using up oxygen on the
bottom of the shelf. These shelf-bottom waters can get rather dense, due partly to
brines released from ice formation above, and then flow off the shelf, carrying
regenerated nutrients and, potentially, contaminants into the central basin.