International Polar Year 2007–2008 - WMO

Fig. 2.2-3. Track of
the NABOS Cruise
aboard R/V Kapitan
Dranitsyn showing
mooring locations
and affiliations in
October 2008.
(Source: Igor Polyakov,
IARC, November 2008)
158
IPY 20 07–20 08
BeringStrait.html). The expansion of the array during
IPY provided a number of important insights. First, the
new sensor systems have provided the first year-round
measurements of stratification in the Bering Strait
region. Second, although instruments are still being
calibrated, preliminary results suggest that the annual
mean 2007 transport had strengthened to around 1Sv,
comparable with the previous high northward flow
of 2004, which had been related to a reduction in the
southward winds. The increased flow, coupled with a
very modest warming, suggests the Bering Strait heat
flux in 2007 was also at a record-length high. Servicing
of these moorings also took place during the fall and
summer of 2008 and 2009 on board the Akademik
Lavrentiev and the Professor Khromov.
Tracking the inflows downstream: the NABOS arrays
across the circum-Arctic Boundary Current are
our main source of information on the Atlantic inflow
branches once they enter the Arctic Ocean and subduct
to intermediate depths. The cruises of the RV Viktor
Buynitsky in 2007 and of the Kapitan Dranitsyn in
2008 were the sixth and seventh in an annual series
designed to service an increasingly international array
of instruments set across the circum-Arctic boundary
current (Fig. 2.2-3). The program has had major successes,
notably the recovery of two-year-long datasets
from at least two of the moorings (M4, M6; Fig. 2.2-3),
which confirmed the presence of strong seasonal os-
cillations in the Atlantic Water, and the hydrographic
cross-sections, which confirmed the continuation of
warming along this boundary [based on a standard
JOIS/C3O transect, Fiona McLaughlin and Eddy Carmack
(pers. comm., 2009), later confirm the arrival of
the latest warm pulse in the Atlantic-derived sublayer
at the southern margins of the Canada basin in 2007];
one very long MMP record near Svernaya Zemlya
showing bursts of very warm (2°C) Atlantic water up to
90m right through the halocline in 2008.
The losses of equipment and data in this difficult
environment have also prompted certain changes in
NABOS strategy for the future however, (i) a limited
number of very well equipped moorings capable of
surviving deployments of at least two year’s duration
now seem appropriate to form the frame of a climateoriented
observational network; (ii) no MMPs will be
used for these moorings in future because, at this
location and in this boundary current, they have
shown low reliability; (iii) NABOS will deploy clusterlike
groups of several (five or more moorings) each
year, moving this cluster from one climatological
mooring location to another so as to investigate the
processes responsible for driving change at these
sites. As the behaviour of the Atlantic Current branches
in the Nansen Basin is still of considerable scientific
interest, the continuation of the NABOS array in some
form remains a priority.