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a Kwok (2005) b Kwok et al. (2006) c Agnew et al. (2006)

a Kwok (2005) b Kwok et al. (2006) c Agnew et al. (2006)

Arctic Ocean. Since the Gulf was ice-free during the summer, as typical, most of the export would be first-year ice leaving during autumn and winter. On assumption of 1-m average thickness (perhaps high because the gate traverses the Bathurst polynya), the average export would have been 85 km3/year. There was also an average export of ice from M'Clure Strait to the Beaufort Sea, although in smaller quantity and with occasional reversals (there was net import from the Beaufort in 2000). The average export would have been 80 km3/year, on assumption of 4-m average thickness

(McLaren et al. 1984). Only the entry points to the Sverdrup Basin accepted a net influx of ice to the Canadian polar shelf, but the amount was small (8 x 103 km2/year or 7 km3/year if ice was 3.4 m thick). This net influx is consistent with the analysis of Melling (2002), although its value is only about 20% of that implied by Melling's analysis.

The analysis has been extended to the cold months of 2002-2003 to 2005-2006 using AMSR-E (Agnew et al. 2006). The pattern of flux, with export from Amundsen Gulf and M'Clure Strait and import into the Sverdrup Basin, was continued during this period. However, the average out-fluxes from Amundsen Gulf and M'Clure Strait during this 4-year period (14 and 5 x 103 km2/year) were smaller than during the preceding 5-year period (85 and 20 x 103 km2/year) and the influxes to the Sverdrup Basin (30 and 6 x 103 km2/year) were larger (6 and 2 x 103 km2/ year). There is obviously inter-decadal variability, as inferred by Melling (2002), which may respond to cycles in atmospheric circulation; it may also be that ingress of pack ice to the Sverdrup Basin was easier after the extensive loss of old ice within the Archipelago in 1998.

On the other side of the Canadian Archipelago, ice generally moves from the Canadian polar shelf into Baffin Bay. Agnew et al. (2006) have also used images acquired via AMSR-E to estimate ice flux into Baffin Bay during the colder months of 2002-2003 to 2005-2006: annual average fluxes were 48, 10 and 9 x 103 km2/ year via Lancaster, Jones and Smith Sound, respectively. The associated fluxes of volume were 49, 10 and 9 km3/year per metre of ice thickness.

Agnew and Vandeweghe (2005) have calculated the ice flux during 2002-2004 through a gate across central Baffin Bay; the average over the 2-year interval was 690 x 103 km2/year southward. Clearly the efflux of ice from the Canadian polar shelf during the last decade has been larger than the influx, implying that much of the ice exported to the Labrador Sea has been formed there and not in the Arctic Ocean itself. Moreover, the southward flux of ice through Baffin Bay actually exceeded that through Fram Strait over the same period in terms of area (590 x 103 km2/year: Agnew and Vandeweghe 2005). However because the Fram Strait flux is primarily old ice and that the Baffin flux is primarily seasonal, the export of ice volume through Baffin Bay is probably the lesser.

Table 9.5 summarizes the ice flux values discussed here.

Table 9.5 Annual average areal flux of ice between the Canadian polar shelf and Baffin Bay during the last decade. The unit is 1,000 km2. Arctic exports have positive value

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