Ocean Circulation and Geochemistry
Oxygen Saturation (%)
Winter shelf waters have been
thought to reach rather high densi-
ties. Although there are observations
of this, establishing a direct connec-
tion to the deep waters, which seems
essential to models of deep water for-
mation in the Arctic, has been elu-
sive. We found during AOS-94 what
is perhaps an important new piece to
this puzzle: At station 22, on the pe-
riphery of the Makarov Basin, we saw
a bolus of water dense enough to be
centered at 1000 m, with unique
characteristics indicating that it could
have come only from the shelf. Relatively high CFC concentrations confirmed
Saturation of oxy-
gen vs. pressure for
its recent origin. This bolus has entered the Makarov Basin and now slowly
the AOS-94 stations
freshens the deep water. This may be the first direct observation of "new"
over the Chukchi
shelf (Stations 16).
high-density shelf water actually in the deep basins.
There is a weak, deep horizontal salinity gradient across the Chukchi
Makarov sector, with higher deep salinities near the pole on the Canadian side
of the Lomonosov Ridge. At station 22 in the southeastern Makarov Basin we
saw deflections in the salinity isopleths due to the bolus of relatively fresh,
cold, young deep water.
Isopycnals generally slope slightly down from pole to shelf across the domain
covered by this section, with more significant deflections associated with each
principal bathymetric feature, and circulation associated with the bolus of
young deep water found at station 22. Sharp isopycnal slopes over the Lomono-
sov Ridge (stations 3034) showed geostrophic adjustment to relatively strong
upper-layer flow along the ridge crest. The most intense deep deflections in
sigma-2 were found on the Eurasian flank of the Lomonosov Ridge and, to a
lesser extent, on the southeast flank of the Makarov Basin.
On their own the AOS-94 CTD/hydrographic/tracer/contaminant data are
a unique, well-placed and important data set, providing the first reference-
quality section across the Chukchi Abyssal Plain and Makarov Basin and a
careful, synoptic section of closely spaced stations across the Eurasian flank of
the Lomonosov Ridge near the North Pole. The AOS-94 section also joins to
the Oden 1991 section in the Makarov Basin near the Lomonosov Ridge, and
these in turn can be joined to the Polarstern 1987 Nansen Basin section to
form a nearly complete, shelf-to-shelf trans-Arctic section of high-quality sur-
face-to-bottom multi-tracer stations.