Sea-surface temperature and krill catches around South Georgia in December–February 1989–1991 and 1999–2001
Monitoring of sea-surface temperatures (SSTs) in Subarea 48.3, which includes satellite surveys with GOES-E, Meteosat and in situ monitoring, together with further analysis of SST maps, provides continuous information on hydrological conditions in the area. Analyses of the data at the beginning of each summer season could enable us to evaluate the potential for conducting a krill fishery in the area during the entire year. The reliability of these forecasts could be appraised by comparing them with krill catches obtained under various hydrological conditions. In comparison with the early 1990s, the period from December to February in the late 1990s and early 2000s showed a considerable decrease in mean SST off South Georgia. This observation is especially obvious for the northern shelf waters where the mean SST dropped from 3.96°C in 1990/91 to 2.05°C in 2000/01. During that period, the SST anomaly sign changed from positive to negative: on average, the December–February anomaly was up to +0.71°C in 1990/91, whereas it was -1.2°C in 2000/01 (for the 1999/2000 season the SST anomaly was -0.62°C). The observed cooling of South Georgia waters had a negative effect on fi shing activities in the area. The total catch of krill was 81 369 tonnes in 1989/90 and 123 562 tonnes in 1990/91. However, it dropped to 39 766 tonnes in 2000/01. The SST maps for 1999–2001 showed a prominent
advection of Weddell Sea waters to the northwest of South Georgia and a weakening of the Antarctic Circumpolar Current (ACC) infl uence. Under these hydrological conditions, krill that drifted along with Weddell Sea waters failed to form stable concentrations on the shelf and was transported instead further out to open sea.