International Polar Year 2007–2008 - WMO

Inputs to the Arctic Ocean: what
questions should we be testing?
Q: What is the relative importance of the two main
Atlantic inflow branches in carrying ocean climate
‘signals’ from the Nordic Seas into, around and through
the Arctic deep basins?
A: The basis for this as a focus question is the
suggestion put forward by Bert Rudels (Univ. Helsinki)
at the Arctic Science Summit Week, Bergen 2009,
that the colder fresher Barents Sea inflow branch
may dominate the Arctic Ocean beyond the Nansen
Basin, with the Fram Strait branch seldom penetrating
beyond the Lomonosov Ridge. Dmitrenko et al., (in
press) would seem to agree. If so, the source of the
recent warming — so graphically described along
the boundary of the Laptev Sea and Canada basin by
Polyakov et al., (2005; 2007), Dmitrenko et al., (2008a,b),
Carmack (pers. comm.) and others — will effectively
have been reassigned. As illustrated in the various
panels of Fig. 3.2-1, the essence of Rudels’ argument is
that beyond the Gakkel Ridge the Θ-S characteristics
of the Atlantic-derived sublayer are closer to those
of the Barents Sea Branch (BSB in Fig. 3.2-1) than the
Fram Strait Branch (FSB). Testing Rudels’ idea will be
an important task for the legacy phase to resolve,
but the tools to do so are well proven: detailed shipborne
hydrography, sustained flux measurements
through the northeast Barents Sea, and continued
or intensified coverage of the boundary currents
along the Eurasian margin of the Nansen basin from
the point where both branches first flow together to
PA R T T H R E E : I PY OBSERVING SYS T E M S , T H E I R L E G AC Y A N D DATA M A N AG E M E N T
3.2 Towards an Integrated Arctic Ocean
Observing System (iAOOS)
Lead Authors:
Robert Dickson and Eberhard Fahrbach
Contributing Authors:
Sara Bowden and Jacqueline Grebmeier
Reviewers:
John Calder, Eduard Sarukhanian and Colin Summerhayes
The following chapter presents selected examples of new ideas that have emerged from
the enhanced ocean-observing effort of IPY 2007–2008 on the role of the Northern Seas in
climate. This is an incomplete sampling of the questions that must be asked to determine a
sustainable observing system in the legacy phase following the completion of IPY.
their supposed points of separation at the Lomonosov
ridge. This lends further support to the continuation
of a modified NABOS (Nansen and Amundsen Basins
Observational System) array across this boundary. The
research team is likely to include Bert Rudels (Univ.
Helsinki), Ursula Schauer (AWI), Øystein Skagseth (IMR
Bergen), and Igor Polyakov (IARC).
Q: Where can we expect the recent extreme warmth of
the Atlantic–derived sublayer of the Arctic Ocean to have
its main climatic impact?
A: Very recently, the temperature and salinity of
the waters flowing into the Norwegian Sea along the
Scottish shelf and Slope have been at their highest
values for >100 years. At the ‘other end’ of the inflow
path, the ICES Report on Ocean Climate for 2006
showed that temperatures along the Russian Kola
Section of the Barents Sea (33º30’E) had equally never
been greater in >100 years (Holliday et al., 2007). As
already noted, Polyakov et al., (2005; 2007), Dmitrenko
et al., (2008a, b) and others have documented the
onward spread of the most recent pulses of warmth
along the Eurasian boundary of the Arctic Ocean.
When the IPY began in March 2007, the consensus
view would likely have been that a 100-year maximum
in the warmth of the inflow to the Arctic must in some
way be bound up with an increased melting of Arctic
sea ice. Since then our ideas have altered in response to
new simulations by a group from the Alfred Wegener
Institute (M. Karcher, pers. comm., also Karcher et al.,
2007; 2008), which suggest that, as the warm Atlantic-
o b s e r v I n g s Y s t e m s a n d d a t a m a n a g e m e n t 371