Stepwise consolidation of glacigenic sediments of the Prydz Bay

A series of samples from the five sites drilled across the continental shelf and upper slope in Prydz Bay during ODP Leg 119 were consolidation tested in an oedometer. Preconsolidation stresses increase downcore at Sites 739 and 742 in a stepwise manner, and the steps are interpreted to represent periods of increased action of grounded glaciers covering the entire shelf. By the use of theoretical ice sheet surface profiles giving the range of possible ice thicknesses, sediment loading and subsequent erosion seem to be the most important factor for increasing the overconsolidation ratios, and a total glacial erosion exceeding 1 km is possible. Four separate steps in consolidation, here termed "load events" have been identified. The lowermost load event, 1, is correlated to the onset of glaciations reaching the shelf edge and an early period of extensive glaciations, starting in early Oligocene or possibly earlier. Glacial activity related to the buildup of ice in West Antarctica in the late Miocene is tentatively correlated to load event 2. Event 3 is the trace of relatively extensive glacial erosion probably in the Pliocene, whereas the upper step in preconsolidation stress, load event 4, results from the last glaciation reaching the shelf edge, possibly during the late Weichselian. Correlations to other data related to Antarctic glacial history are, however, hampered by the poor age control of the cored diamictites. Consolidation tests may provide a tool for finding the position for hiatuses and unconformities formed subglacially and obscured by subglacial reworking.

(Table 1) Ice floe size and other characteristics during aerial observations in Prydz Bay, Antarctica

On the basis of aerial photographs of sea ice floes in the marginal ice zone (MIZ) of Prydz Bay acquired from December 2004 to February 2005 during the 21st Chinese National Antarctic Research Expedition, image processing techniques are employed to extract some geometric parameters of floes from two merged transects covering the whole MIZ. Variations of these parameters with the distance into the MIZ are then obtained. Different parameters of floe size, namely area, perimeter, and mean caliper diameter (MCD), follow three similar stages of increasing, flat and increasing again, with distance from the open ocean. Floe shape parameters (roundness and the ratio of perimeter to MCD), however, have less significant variations than that of floe size. Then, to modify the deviation of the cumulative floe size distribution from the ideal power law, an upper truncated power-law function and a Weibull function are used, and four calculated parameters of the above functions are found to be important descriptors of the evolution of floe size distribution in the MIZ. Among them, Lr of the upper truncated power-law function indicates the upper limit of floe size and roughly equals the maximum floe size in each square sample area. L0 in the Weibull distribution shows an increasing proportion of larger floes in squares farther from the open ocean and roughly equals the mean floe size. D in the upper truncated power-law function is closely associated with the degree of confinement during ice breakup. Its decrease with the distance into MIZ indicates the weakening of confinement conditions on floes owing to wave attenuation. The gamma of the Weibull distribution characterizes the degree of homogeneity in a data set. It also decreases with distance into MIZ, implying that floe size distributes increase in range. Finally, a statistical test on floe size is performed to divide the whole MIZ into three distinct zones made up of floes of quite different characteristics. This zonal structure of floe size also agrees well with the trends of floe shape and floe size distribution, and is believed to be a straightforward result of wave-ice interaction in the MIZ.

(Table 1) Number of invertebrate species per bottom trawl haul in the Kapp Norvegia to Halley Bay area on cruise EASIZ I (ANT-XIII/3) and in the Kapp Norvegia - Austasen area on cruise EASIZ III (ANT-XVII/3)

Ecological work carried out on the Antarctic and Magellan shelves since the first IBMANT conference held at the UMAG, Punta Arenas in 1997 is summarized to identify areas where progress has been made and others, where impor- tant gaps have remained in understanding past and present interaction between the Antarctic and the southern tip of South America. This information is complementary to a review on shallow-water work along the Scotia Arc (Barnes, 2005) and recent work done in the deep sea (Brandt and Hilbig, 2004). While principally referring to shipboard work in deeper water, above all during the recent international EASIZ and LAMPOS campaigns, relevant work from shore stations is also included. Six years after the first IBMANT symposium, significant progress has been made along the latitudinal gradient from the Magellan region to the high Antarctic in the fields of biodiversity, biogeography and community structure, life strategies and adaptations, the role of disturbance and its significance for biodiversity, and trophic coupling of the benthic realm with the water column and sea ice. A better understanding has developed of the role of evolutionary and ecological factors in shaping past and present-day environmental conditions, species composition and distribution, and ecosystem functioning. Furthermore, the science community engaged in unravelling Antarctic-Magellan interactions has advanced in methodological aspects such as new analytical approaches for comparing biodiversity derived from visual methods, growth and age determination, trophic modelling using stable isotope ratios, and molecular approaches for taxonomic and phylogenetic purposes. At the same time, much effort has been invested to complement the species inventory of the two adjacent regions. However, much work remains to be done to fill the numerous gaps. Some perspectives are outlined in this review, and sug- gestions are made where particular emphasis should be placed in future work, much of which will be developed in the frame of SCAR's EBA (Evolution and Biodiversity in the Antarctic) programme.

Concentration of phenols in bottom sediments from the Kandalaksha Bay, White Sea

Data on distribution of organic carbon and phenols near the top of Kandalaksha Gulf, one of the largest gulfs of the White Sea, are presented. Investigations carried out the port city of Kandalasksha indicate that bottom sediments of the area adjoining the port contain synthetic phenols and have elevated concentrations of organic carbon. But in general sediments of this part of the gulf have near-normal concentration and composition of both phenols and organic carbon. This indicates that ecological situation in this area remains near-optimal.

Water chemistry, and body temperature, swimming depth and stomach contents of Arctic char (Salvelinus alpinus) in inner Frobisher Bay, Canada

The influence of salinity, temperature and prey availability on the marine migration of anadromous fishes was determined by describing the movements, habitat use and feeding behaviours of Arctic char (Salvelinus alpinus). The objectives were to determine whether char are restricted to the upper water column of the inter-/subtidal zones due to warmer temperatures. Twenty-seven char were tracked with acoustic temperature/pressure (depth) transmitters from June to September, 2008/2009, in inner Frobisher Bay, Canada. Most detections were in surface waters (0-3 m). Inter-/subtidal movements and consecutive repetitive dives (maximum 52.8 m) resulted in extreme body temperature shifts (-0.2-18.1 °C). Approximately half of intertidal and subtidal detections were between 9-13 °C and 1-3 °C, respectively. Stomach contents and deep diving suggested feeding in both inter-/subtidal zones. We suggest that char tolerate cold water at depth to capture prey in the subtidal zone, then seek warmer water to enhance feeding/digestion physiology.

Relative sea-level history of Marguerite Bay, Antarctic Peninsula derived from optically stimulated luminescence-dated beach cobbles

Calmette Bay within Marguerite Bay along the western side of the Antarctic Peninsula contains one of the most continuous flights of raised beaches described to date in Antarctica. Raised beaches extend to 40.8 m above sea level (masl) and are thought to reflect glacial isostatic adjustment due to the retreat of the Antarctic Peninsula Ice Sheet. Using optically stimulated luminescence (OSL), we dated quartz extracts from cobble surfaces buried in raised beaches at Calmette Bay. The beaches are separated into upper and lower beaches based on OSL ages, geomorphology, and sedimentary fabric. The two sets of beaches are separated by a prominent scarp. One of our OSL ages from the upper beaches dates to 9.3 thousand years ago (ka; as of 1950) consistent with previous extrapolation of sea-level data and the time of ice retreat from inner Marguerite Bay. However, four of the seven ages from the upper beaches date to the timing of glaciation. We interpret these ages to represent reworking of beaches deposited prior to the Last Glacial Maximum (LGM) by advancing and retreating LGM ice. Ages from the lower beaches record relative sea-level fall due to Holocene glacial-isostatic adjustment. We suggest a Holocene marine limit of 21.7 masl with an age of 5.5-7.3 ka based on OSL ages from Calmette Bay and other sea-level constraints in the area. A marine limit at 21.7 masl implies half as much relative sea-level change in Marguerite Bay during the Holocene as suggested by previous sea-level reconstructions. No evidence for a relative sea-level signature of neoglacial events, such as a decrease followed by an increase in RSL fall due to ice advance and retreat associated with the Little Ice Age, is found within Marguerite Bay indicating either: (1) no significant neoglacial advances occurred within Marguerite Bay; (2) rheological heterogeneity allows part of the Antarctic Peninsula (i.e. the South Shetland Islands) to respond to rapid ice mass changes while other regions are incapable of responding to short-lived ice advances; or (3) the magnitude of neoglacial events within Marguerite Bay is too small to resolve through relative sea-level reconstructions. Although the application of reconstructing sea-level histories using OSL-dated raised beach deposits provides a better understanding of the timing and nature of relative sea-level change in Marguerite Bay, we highlight possible problems associated with using raised beaches as sea-level indices due to post-depositional reworking by storm waves.

Composition of bottom sediments and interstitial waters from the Gdansk Bay

Contents of mercury and zinc in reduced sediments and interstitial waters of the Gdansk Bay in the Baltic Sea were investigated. It was found that sediments contain 0.7 ppm Hg, of which 0.008 ppm.(0.4% of total) is dissolved in interstitial water, and 91 ppm Zn, of which 0.15 ppm (0.45% of total) is dissolved in interstitial water. Differences in contents in different layers (0-5 and 25-30 cm) can be attributed to anthropogenic influence. Aderage concentration of mercury in the upper sediment layer is 27% higher and one of zinc is 40% higher than those found in the lower sediment layer. In addition, distribution of zinc in grain size fractions of the sediments was investigated, and some data on cadmium content were obtained.

Near real time surface ocean velocity in the Bay of Biscay - Basque Country from Mai to September 2016

The data set consists of maps of total velocity of the surface current in the Southeastern Bay of Biscay averaged over a time interval of 1 hour around the cardinal hour. Surface ocean velocities estimated by this HF Radar(4.65 MHz) are representative of the upper 2-3 meters of the ocean. The main objective of near real time processing is to produce the best product from available data at the time of processing. Total velocities are derived using least square fit that maps radial velocities measured from individual sites onto a cartesian grid. The final product is a map of the horizontal components of the ocean currents on a regular grid in the area of overlap of two or more radar stations.