CCAMLR

Interrelations between environmental variables, and between those variables and krill CPUE are discussed. Some reliable relationships is revealed. Based on those of krill abundance interannual fluctuations relationship hypothesis is formulated.

During the Italian Antarctic Expeditions to the Ross Sea, in the years 1989 - 1994, using the 38 and 120 kHz BioSonics dual-beam hydroacoustic system, numerous swarms of krill Euphausia superba Dana were registered . Analysis of their physical parameters was carried out. It is known that insects appear to disperse according to a reaction diffusion model with a constant diffusion coefficient (Okubo, 1980, 1986). It was assumed that the above mentioned model can also be applicable to krill swarms. Using physical parameters of the krills' swarm (density, length), the above assumption was verified.
It was found that the vertical density pattern of krills' swarm, with a mean density of up to 1000 individuals/m3, is consistent with the insect model predictions. That is why cohesive forms of krill aggregations are usually termed "swarms" rather than "schools", which is normally used for fish groupings.

Historical hydrographic data from Bransfield Strait and the region west of the Antarctic Peninsula were analyzed to provide a description of water mass distributions and circulation patterns. Circumpolar Deep Water (CDW), which is characterized by temperatures above 1.0°C, salinities of 34.6 to 34.73 and oxygen values below 4.5 ml 1-1, is the most prominent water mass in this region, is found between 200 and 700 m, and is present in all seasons throughout the region examined. Below 200 m this water mass floods the continental shelf west of the Antarctic Peninsula. CDW is also found in Bransfield Strait, but the distribution is limited to the northern side of the Strait near the South Shetland Islands. Mixing of CDW results in reduction of the oxygen content of the overlying Antarctic Surface Water by 25 to 45%, which suggests an average annual entrainment rate for the west Antarctic Peninsula of 0.7 to 1.43 X 10-6 m s-1. The freshwater input needed to balance the salinity input from CDW is on the order of 0.63 m y-1, which can be supplied by local precipitation and advection of ice into the region from the Bellingshausen Sea, which then melts. The annual heat flux associated with CDW is 12 W m-2 , which is sufficient to melt this amount of ice. A second prominent water mass, Bransfield Strait Water (

The climate of tile Western Antarctic Peninsula (WAP) region is distinguished by large seasonal and interannual variability and by the occurrence of seasonal sea ice which changes the ocean-atmosphere interface, affects tile surface albedo, and modifies the annual temperature cycle. Air temperature records for several peninsula stations have been examined, and the annual progression of surface air temperatures show an along-peninsula gradient indicative of a contrasting influence of maritime versus continental climatic regimes. WAP temperature records show the largest and most significant warming trends for the Antarctic with mid-winter temperature increases of 3° to 5°C over the past half-century. Increased temperature variability in fall and winter is linked to tile high interannual variability of sea ice coverage. Linear regression analysis shows a significant (99.9%) anti-correlation between air temperature and sea ice extent, even after accounting for serial correlation in the two time series. There are distinct seasonal lead/lag relationships between temperature and sea ice in this region, which underscore the complexity of polar feedback mechanisms. The more than 45 year Faraday air temperature record shows a significant (95% confidence level) correlation with the Southern Oscillation Index (SOI) and coherences between both temperature and sea ice with the SOI suggest teleconnections between the WAP and lower latitudes. This evidence suggests that the WAP area, the focus of the Palmer Long-Term Ecological Research program, is sensitive to climate variability. Consequently, because of strong coupling between temperature, sea ice and the antarctic marine ecosystem, the Palmer LTER is ideally located for the study of ecological responses to global change.