Research on submesoscale eddy and front near the South Shetland Islands(Antarctic Peninsula)using seismic oceanography data

The submesoscale processes, including submesoscale eddies and fronts, have a strong vertical velocity, can thus make important supplements to the nutrients in the upper ocean. Using legacy multichannel seismic data AP25 of cruise EW9101 acquired northeast of the South Shetland Islands(Antarctic Peninsula) in February 1991, we identified an oceanic submesoscale eddy with the horizontal scale of ~4 km and a steep shelf break front that has variable dip angles from 5° to 10°. The submesoscale eddy is an anticyclonic eddy, which carries warm core water, can accelerate ice shelves melting. The upwelling induced by shelf break front may play an important role in transporting nutrients to the sea surface. The seismic images with very high lateral resolution may provide a new insight to understand the submesoscale and even small-scale oceanic phenomena in the interior.

The features and generation of CWB near the South Shetland Islands in austral summer of 1987

-STD Data obtained from the Third Chinese National Antarctic Research Expedition from January to February 1987 in the region near the South Shetland Islands are used to investigate an oceanic front, continental water boundary (CWB), north of the South Shetland Islands. The characteristics of the CWB in surface and subsurface layers as well as deep layer are discussed respectively. The estimations of the geostrophic currents and the baroclinic deformed radius Rbc in this area show that the flow along the front is in the geostrophic equilibrium approximately, and the formation of the front is mainly due to the strong boundary current north of the South Shetland Islands. Its length along the front is estimated to be about 360 km and its width across the front is about 30 km.

PRELIMINARY REPORT ON THE PELAGIC POLYCHAETES FROM THE SOUTH SHETLAND ISLANDS,BISCOE ISLANDS AND THEIR VICINITIES

This report provides a result obtained by the First Chinese Antarctic and Southern Ocean Expedition. Specimens were collected by investigators of the Second Institute of Oceanography, SOA, with plankton nets in February and March of 1985 from the South Shetland Islands, the Biscoe Islands and their vicinities, between 61°15'20S-65°30'16S, 56°18'72W-67°59'45W. Eight species belonging to 5 genera in 4 families have been identified, of which 4 species, namely Maupasia coeca Viguier, Rhyn-chonerella petersii (Langerhans), Rhynchonerella bongraini (Gravier), and Tomopteris planktonis Aps-tein are recorded for the first time from the South Shetland Islands and 2 species, namely Rhynchonerella bongraini (Gravier), and Tomopteris carpenteri Quatrefages are endemic species of Antarctica.

Microbes in the area of the South Shetland Islands

Investigations were made on the microbes in the air, bottom sediments, surface seawater in the sea area of the South Shetland Islands during December, 1986～March, 1987.The results obtained show that: from the air over the South Shetland Islands and the Maxwell Bay,the detection rate of terrigenous microbes was more than 90% and their amount was generally a few CFU/m3; the detection rate of marine microbes was more than 50% and their amount only 1 CFU/m3. The amounts of air-borne microbes over the surveyed area were the witness to their diurnal variations. They were influenced to some extent by nearby islands. Air temperature and relative humidity,etc. were factors affecting their quantitative variations.The bacterial amount of the outshore surface sea water in the Great Wall Bay, Antarctica was about n×10 CUF/cm3 (0≤n<10, the same below), the amount of microbes decreased with the monthly dropping of seawater temperature and showed a state of diurnal variations. The seawater in the Bay has been fairly clean. The microbial community consisted of at least thirteen genera,in which pseudomonas was common. In the intertidal zone of the Deception Island,there were only a few CFU of bacteria per cubic meter in seawater; and n×10 CFU/g (w. w) in the surface sediment;and n×10 CFU/g(w. w) in the volcano ash.The results reveal the general features of the microbes from the air,sea and land in the South Shetland Islands, Antarctica. It provides data for further study of microbial resources in that area.

PRELIMINARY STUDY ON THE OXYGEN-MINIMUM LAYER IN WATER AREA ADJACENT TO SOUTH SHETLAND ISLANDS AND NORTH OF ARDLEYD ISLAND, ANATRCTICA, IN SUMMER

In this paper, a distribution ol the oxygen-minimum layer in the sea area adjacent to the South Shetland Islands and north of the Ardleyd Island, Antarctica, in summer is discussed.The vertical distribution of oxygen in oxygen-minimum layer has the following features: 1). The depth at which the oxygen content greatly decreases is coincident with the depth of pycnocline; 2). There is a thick water layer with low oxygen content; 3). The oxygen-minimum layer occurs below the thermocline and coincides with the depth at which the temperature mostly increases. According to preliminary result of correlation analysis, the variation of oxygen-minimum layer is related to physical preperties of the circulation and biochemical process in deep layer of the ocean.

Paleomagnetism of Early Tertiary volcanics in the South Shetland Islands and its tectonic implications

A total of 334 oriented volcanic samples of Early Tertiary were collected for a paleomagnetic study from 43 sampling sites in the South Shetland Islands,Antarctica.Paleomagnetic study indicates that the South Shetland Islands and Antarctic Peninsula were situated in or close to their present position in Early Tertiary. Furthermore, it is also suggested that a counterclockwise rotation about 15 degrees related to the relative movement between South America and Antarctica took place in north of Antarctic Peninsula since Paleocene.

ANALYSIS OF THE STOMACH CONTENTS OF ANTARCTIC KRILL, EUPHAUSIA SUPERBA DANA

Diet components of Euphausia superba of 12 sexual maturity stages from the adjacent waters off the South Shetland Islands, Antarctica were analysed. The major points observed are summaried as follows: 135 taxa of nano- and microorganisms were found in stomach contents of Euphausia superba, of which, the diatoms make up 60% of the total species number. Planktonic nano- diatoms and nano- flagellates smaller than 20μm in diameter accounted for 85 % of diet total number. The dominant species in the stomach contents were Nitzschia angulata f. minima, N. curta f. minima, N. curta,Chrysostomum sp. , the mean cell number of these species was about 56. 99 cells/ind. , The stomach fullness increases gradually with the sexual mature of the krill.

Spatial variability of soil nutrients in Punta Fort William,Greenwich Island,maritime Antarctic

This study aims to report baseline soil nutrients, specifically the organic carbon, nitrogen and phosphorus profile, in soil samples collected from Puntta Fort William on Greenwich Island in maritime Antarctic. Samples were collected along two transect lines during the early summer of 2008. Ward＇s method of hierarchical agglomerative clustering was employed to group the sampling points based on their physico-chemical properties. In this context, the soil samples can be grouped into three major clus- ters： （1） Samples with intensive biological activities, （2） samples from the area recently exposed by glacial retreat and （3） samples from barren and dried areas. Nutrient contents in Punta Fort William are driven by the intensity of biological activities as well as melt water from the Qnito glacier.