|significant quantities of
glacial ice from the Greenland Ice sheet. This freshwater flux
plays a significant role in the Thermohaline Circulation (THC) of
the world oceans. The region is also home to the North Water
Polynya (NOW). A Canadian led international programme studied
this polynya in great detail and showed that it is the most
biologically productive polynya in the whole of the Arctic. Recently
the International Arctic Polynya Programme stated the following about
the NOW (IAPP: PACE document, 2004).
The North Water has been a reliably recurrent and high-production ecosystem for recorded history, as recently confirmed on the century scale by the marine sedimentary record (Hamel et al., 2002). The main players (from viruses to whales) and processes (from atmospheric exchange to sediment burial) governing the current functioning of this ecosystem are known (Deming et al., 2002). The internal factors accounting for the temporal and spatial disposition of the polynya are unambiguous: e.g., the timing and force of the wind arriving from the west and the formidable ice bridge that straddles Kane Basin during the open-water season. Examination of two decades of satellite imagery suggests that the physical system is poised for change, given the evidence that features of the ice bridge have been weaker in recent years (Barber et al., 2001). If an external change in Arctic Ocean circulation also occurs (Johnson et al., 1999), then the chemical make-up of the source waters to the polynya may well shift. Tremblay et al. (2002a) argue that the nitrate to silicate ratio is delicately poised now. A shift away from silica in the source waters may reduce the extent and magnitude of the diatom bloom in the North Water, which in turn will affect the higher trophic levels. There is a need for ongoing measurements in the North Water in particular, so that the existing three-year NOW data sets can comprise the beginning of the long-term database required to make and to test predictions (IAPP: PACE document, 2004).
|(NEWATER, 1993). The importance
of the region was highlighted by the Arctic Ocean Sciences Board,
through the International Arctic Polynya Programme, whose first
programme (NEWATER) was directed to the region in the early 1990s. The
NEWATER programme dataset (multidisciplinary) provides a valuable
baseline against which we can judge consequences of subsequent and
future climate change (Overland et al., 1995, Hirch and Deming, 1997).
This dataset is particularly valuable as it the only multidisciplinary
dataset available from a time before significant change was detected in
the Arctic (early 1990s). Since NEWATER the area of the NEW polynya has
slowly increased steadily in size. In the summer of 2001 the
dramatic northerly retreat of sea ice in the East Greenland Current
(EGC) united with the polynya to form what one could describe as an
almost open continental shelf sea. This scenario, possibly
unprecedented in recorded history, continued for the next four years
and led to the NEW being described as having morphed into the Marginal
Ice Zone (MIZ) (Smith and Barber, 2007). In fact one could legitimately
ask if there is still a NEW polynya or has it ceased to function as
However in the summer of 2005, which corresponded to a new minimum in the extent of sea ice in the Arctic, the NEW returned, albeit smaller than usual. The continued retreat of Arctic sea ice continued in 2006 and in 2007 it surpassed all previous records, reducing to an area of only 4.1 million km2 (NSIDC, 2007). These years were associated with a significant increase in the amount of ice over the NEG continental shelf, which in turn led to the area of the NEW being substantially smaller than the mean (Fig. 2). In fact the 2007 NEW was the smallest since satellite records began over 30 years ago; it could almost be discribed as non-existent. Thus the likely response of the polynya system to Arctic warming is now unclear. Until recently the response of the polynya system was consistent with an ice retreat and conversion into a MIZ. Recent events suggest that a plausible alternative fate is actually a reduction or near-disappearance of the NEW polynya, possibly driven by an increased export of ice through Fram Strait.
What is clear is that the NEW polynya has experienced a fundamental shift in its operation since the early 1990s. This undoubtedly affects the physical, biological and chemical functioning in the polynya, and as such must impact ecosystem dynamics. Although a few small-scale disciplinary studies have been conducted since NEWATER, no systematic revaluation of the physical, biological and chemical processes has been undertaken.