Ocean fluxes

To estimate fluxes from site-specific time series it is assumed that the mooring data can represent, through weighting, the cross-sectional fluxes. Analysis of data from August 2001 to August 2004 of a modified array provided surface layer (0-60 m) current measurements from % and / way across the strait as well as measurements at the southern and northern sites. These data indicate that in winter and spring, the eastwards currents are similar across the southern 2/3 of the strait, while in summer and fall the currents of the southern mooring should be reduced to 55% to represent the mean currents observed over 2/3 of the southern strait. This provides information to better estimate the total fluxes through the cross-section for the sparser arrays prior to 2001. Further details on the estimation of fluxes can be found in Prinsenberg and Hamilton (2005) and Melling et al. (2008).

Fluxes are calculated relative to a salinity of 34.8 and a temperature of -0.1°C, which represents the salinity and temperature of Atlantic Water in the Arctic Ocean (Aagaard and Carmack 1989). Fluxes clearly show the strong seasonal as well as the interannual variability (Fig. 10). Volume and fresh water fluxes exhibit the same variability driven by the currents, while the heat flux mirrors their variability. All three show maximum magnitudes in the summer and minimum magnitudes in the fall. Volume and freshwater fluxes are positive indicating net transport of Arctic surface waters to the Atlantic Ocean. Heat flux is predominantly negative, indicating that Arctic surface water is colder than Atlantic Water in the Arctic Ocean, and will thus cool the Atlantic Ocean. It has an 8-year mean of -4.1 x 105 W and varies interannually by ±2.0 x 105 W. Seasonal (3-month averages) volume fluxes vary from low values in fall (0.0 Sv in 1998) to high values in summer (1.3 Sv in 2000). Annual means of the volume fluxes vary from 0.4 to 1.0 Sv, and have an 8-year mean of 0.7 Sv. In general, the freshwater flux is 1/15 of the volume flux and follows the volume seasonal variability. It has an 8-year mean of 0.048 Sv and varies interannually by ±0.015 Sv. The 8-year flux data was used to derive the annual cycle, consisting of mean monthly values (Fig. 11). It has a maximum in June of 1.15 Sv and a minimum in December of 0.25 Sv.

3E+06

3E+06

■1.5E+13 1 ■ I.,,,, I ■ i ■ i i ■ i I.,... i ■ i i i, i ■ i i i i J

Aug-98 Feb-99 Aug-99 Jan-00 Jul-00 Jan-01 Jul-01 Jan-02 Jul-02 Jan-03 Jul-03 Jan-04 Jul-04 Jan-05 Jun-05 Dec-05 Jun-06

Time

Fig. 10. Weekly (thin line) and monthly (thick line) estimated volume (top), freshwater (middle) and heat (bottom panel) transports through Lancaster Sound from August 1998 to August 2006.

■1.5E+13 1 ■ I.,,,, I ■ i ■ i i ■ i I.,... i ■ i i i, i ■ i i i i J

Aug-98 Feb-99 Aug-99 Jan-00 Jul-00 Jan-01 Jul-01 Jan-02 Jul-02 Jan-03 Jul-03 Jan-04 Jul-04 Jan-05 Jun-05 Dec-05 Jun-06

Time

Fig. 10. Weekly (thin line) and monthly (thick line) estimated volume (top), freshwater (middle) and heat (bottom panel) transports through Lancaster Sound from August 1998 to August 2006.

Volume Transport

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Fig. 11. Mean monthly volume flux through western Lancaster Sound derived from 8 years of mooring data (Aug 1998-Aug 2006).

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