Spring distribution, size composition and behaviour of krill Euphausia superba in the western Weddell Sea

Polar Record ◽  
1990 ◽  
Vol 26 (157) ◽  
pp. 85-89 ◽  
Author(s):  
B.I. Bergström ◽  
G. Hempel ◽  
H.-P. Marschall ◽  
A. North ◽  
V. Siegel ◽  
...  
Keyword(s):  
Algal Growth ◽  
Size Composition ◽  
Water Layer ◽  
Open Water ◽  
Euphausia Superba ◽  
Weddell Sea ◽  
Ice Algae ◽  
Remotely Operated Vehicle ◽  
Direct Observations ◽  
Pack Ice

AbstractDistribution, size composition and behaviour of Euphausia superba were investigated in the northwestern Weddell Sea (59–63°S, 45–52°W) in October-November 1988 using RMT trawling, SCUBA diving and visual examination of the ice undersurface using a remotely-operated vehicle (ROV). Amounts of krill washed onto the ice during ice-breaking along transects were noted. Juvenile and sub-adult krill were found, often in high numbers, in association with seasonal pack-ice, from the outer marginal ice zone to at least 200 nautical miles [3 50 km] into the closed pack-ice zone. Krill caught with the RMT or observed within or close to the ice usually had full guts. They were frequently seen feeding on ice algae, and seemed to concentrate in pressure zones, melting ice and infiltration layers, ie where ice provided both confining crevices and rich algal growth. During twilight numbers of krill increased in open water close to the ice, though ROV observations at night revealed even greater numbers remaining in ice cavities. Direct observations from deck, by divers and by ROV, confirmed that most of the krill population in the uppermost water layer was confined to ice habitats, though in three out of 20 RMT catches krill reached densities of 0.1 nr3 ie normal summer values. ‘Miniswarms’ forming in early November may indicate seasonal transition of at least part of the krill population from winter ice habitat and grazing on ice-algae, to summer pelagic life and filter-feeding on phytoplankton.

Low phytoplankton biomass and ice algal blooms in the Weddell Sea during the ice-filled summer of 1997

2002 ◽  
Vol 14 (3) ◽  
pp. 231-243 ◽  
Author(s):  
ELSE N. HEGSETH ◽  
CECILIE H. VON QUILLFELDT
Keyword(s):  
Algal Blooms ◽  
Phytoplankton Bloom ◽  
Open Water ◽  
Weddell Sea ◽  
Ice Algae ◽  
Ice Shelf ◽  
Growth Season ◽  
Pack Ice ◽  
Phaeocystis Antarctica ◽  
Upper Mixed Layer

The summer of 1997 was characterized by unusually large amounts of pack ice in the southeastern Weddell Sea, and less than 10% of the area that is commonly ice-free in summer was open. A modest phytoplankton bloom developed in the upper mixed layer in the northernmost area (72°S). The bloom peaked in mid-February with max chlorophyll concentrations of 1.5 μg l−1, and integrated stocks of 55–60 mg m−2. Autotrophic flagellates dominated the biomass (80–90% of the chlorophyll) at first, while diatoms increased relative to flagellates during the bloom. Nutrient deficits, however, indicated that a much larger biomass was produced than was observed. Freezing starting after mid-February probably terminated the bloom, resulting in a pelagic growth season limited in time (less than two months) and space. The sea ice had a distinct brown layer of algae, usually at 1–2 m depth, with average chlorophyll biomass of 10.3 mg m−2. The ice cover exhibited a substantial amount of ridges, with ice algae growing in cavities and other structures, but with lower biomass than in the bands. Ice algae were also found growing on the lower 2 m of the ice shelf (visible at low tide). The overall growth season in the ice lasted several months, and ice algal production may have exceeded pelagic production in the Weddell Sea during the growth season of 1997. Pennate diatoms, like Fragilariopsis curta and F. cylindrus, dominated both in ice and in open water above the pycnocline, while Phaeocystis antarctica dominated in deeper layers and in crack pools. Euphausiids, particularly young stages, were frequently observed grazing on ice algae in ridges and on all sides of the floes, (confirmed by the gut content). Ice algae would thus have served as an ample food supply for the krill in the summer of 1997.

scholarly journals Albedo of the ice covered Weddell and Bellingshausen Seas

2012 ◽  
Vol 6 (2) ◽  
pp. 479-491 ◽  
Author(s):  
A. I. Weiss ◽  
J. C. King ◽  
T. A. Lachlan-Cope ◽  
R. S. Ladkin
Keyword(s):  
Sea Ice ◽  
Surface Albedo ◽  
Austral Summer ◽  
Open Water ◽  
Weddell Sea ◽  
First Year ◽  
Pack Ice ◽  
Bellingshausen Sea ◽  
The Mean ◽  
The Antarctic

Abstract. This study investigates the surface albedo of the sea ice areas adjacent to the Antarctic Peninsula during the austral summer. Aircraft measurements of the surface albedo, which were conducted in the sea ice areas of the Weddell and Bellingshausen Seas show significant differences between these two regions. The averaged surface albedo varied between 0.13 and 0.81. The ice cover of the Bellingshausen Sea consisted mainly of first year ice and the sea surface showed an averaged sea ice albedo of αi = 0.64 ± 0.2 (± standard deviation). The mean sea ice albedo of the pack ice area in the western Weddell Sea was αi = 0.75 ± 0.05. In the southern Weddell Sea, where new, young sea ice prevailed, a mean albedo value of αi = 0.38 ± 0.08 was observed. Relatively warm open water and thin, newly formed ice had the lowest albedo values, whereas relatively cold and snow covered pack ice had the highest albedo values. All sea ice areas consisted of a mixture of a large range of different sea ice types. An investigation of commonly used parameterizations of albedo as a function of surface temperature in the Weddell and Bellingshausen Sea ice areas showed that the albedo parameterizations do not work well for areas with new, young ice.

New records of mummified crabeater seals on islands bordering Admiralty Sound, Weddell Sea

2019 ◽  
Vol 31 (3) ◽  
pp. 109-115
Author(s):  
Javier Negrete ◽  
Leopoldo H. Soibelzon ◽  
Esteban Soibelzon ◽  
Jorge Lusky
Keyword(s):  
Open Water ◽  
Weddell Sea ◽  
Pack Ice ◽  
Breeding Grounds ◽  
Ice Conditions ◽  
Crabeater Seals ◽  
Ice Floes ◽  
Early Breakup ◽  
Natural Trap ◽  
Seymour Island

AbstractNinety-six mummified crabeater seals discovered at Seymour Island (Isla Marambio) are reported. Each specimen was georeferenced, photographed and assigned to five different taphonomic states. Previous work stated that seals at Seymour Island get stranded inland around the breeding season. However, it is not clear if the species breeds in this area. The abundance of crabeater seals and the ice condition along Admiralty Sound (Estrecho Bouchard) were obtained by aerial surveys during spring (2015–17). It appears that the species uses the strait as a passage to breeding grounds. Under heavy ice conditions, the seals become stranded in the middle section of this strait and wander inland through a valley that represents the mouth of an ephemeral stream that ends at the pack ice level. This situation was observed in 2014 and 2015 when recently dead seals were found, evidencing that this natural trap is still active. Nonetheless, in 2016 and 2017, during an early breakup of Admiralty Sound, the seals that remained in the area were more numerous than in 2015 but they did not get stranded inland. This early breakup may encourage the seals to breed there in the presence of open water areas with ice floes.

The Weddell Sea Expedition 2019

2020 ◽  
Author(s):  
John Shears ◽  
Julian Dowdeswell ◽  
Freddie Ligthelm ◽  
Paul Wachter
Keyword(s):  
Sea Ice ◽  
Autonomous Underwater Vehicles ◽  
Remote Sensing Data ◽  
Open Water ◽  
Weddell Sea ◽  
Scientific Programme ◽  
Ice Shelf ◽  
Remotely Operated Vehicle ◽  
Radar Images ◽  
Ice Conditions

<p>The Weddell Sea Expedition 2019 (WSE) was conceived with dual aims: (i) to undertake a comprehensive international inter-disciplinary programme of science centred in the waters around Larsen C Ice Shelf, western Weddell Sea; and (ii) to search for, survey and image the wreck of Sir Ernest Shackleton’s Endurance, which sank in the Weddell Sea in 1915. </p><p>The 6-week long expedition, funded by the Flotilla Foundation, required the use of a substantial ice-strengthened vessel given the very difficult sea-ice conditions encountered in the Weddell Sea, and especially in its central and western parts. The South African ship SA Agulhas II was chartered for its Polar Class 5 icebreaking capability and design as a scientific research vessel. The expedition was equipped with state-of-the-art Autonomous Underwater Vehicles (AUVs) and a Remotely Operated Vehicle (ROV) which were capable of deployment to waters more than 3,000 m deep, thus making the Larsen C continental shelf and slope, and the Endurance wreck site, accessible. During the expedition, a suite of passive and active remote-sensing data, including TerraSAR-X radar images delivered in near real-time, was provided to the ice-pilot onboard the SA Agulhas II. These data were instrumental for safe vessel navigation in sea ice and the detection and tracking of icebergs and ice floes of scientific interest.</p><p>The scientific programme undertaken by the WSE was very successful and produced many new geological, geophysical, marine biological and oceanographic observations from a part of the Weddell Sea that has been little studied previously, particularly the area east of Larsen C Ice Shelf. The expedition also reached the sinking location of Shackleton’s Endurance, where the presence of open-water sea ice leads allowed the deployment of an AUV to the ocean floor to try and locate and survey the wreck. Unfortunately, SA Agulhas II later lost communication with the AUV, and deteriorating weather and sea ice conditions meant that the search had to be called off.</p>

Sea ice conditions during an early spring voyage in the eastern Weddell Sea, Antarctica

Polar Record ◽  
1988 ◽  
Vol 24 (148) ◽  
pp. 49-54 ◽  
Author(s):  
H. Eicken ◽  
T. C. Grenfell ◽  
B. Stonehouse
Keyword(s):  
Open Water ◽  
Early Spring ◽  
Early Summer ◽  
Weddell Sea ◽  
Late Winter ◽  
Main Body ◽  
Pack Ice ◽  
Large Populations ◽  
Differential Expansion ◽  
Ice Pack

AbstractDuring a late winter and early spring oceanographic voyage south into the Weddell Sea the icebreaker RV Polarstern first encountered patches and bands of loose floes in 58°S; these increased over the next 150 km to form closed ice pack which extended 1000 km to the coast. Along the coast the ship encountered almost continuous shore leads and polynyas that formed repeatedly despite persistently low air and sea temperatures. These areas of open water, which are generally visible in USA NOAA and USSR METEOR satellite photographs, form under the action of strong offshore winds that carry the main body of pack ice west and southwest. Grease ice, pancake ice and nilas spreading over the open water are rafted and ridged by windgenerated stresses to double thickness or more; these kinds of ice were continually driven westward, accumulating in a distinctive zone along the eastern edge of the pack ice. Polynyas and leads narrow and disappear temporarily only when winds with northerly or westerly components bring the pack ice toward the land, and reform as soon as offshore winds predominate. Open water, often more than 15 km wide, was present close to the ship throught the spring voyage, facilitating oceanographic work as far south as 77°S. Polarstern's full icebreaking capacity was needed only occasionally when winds temporarily pressed the pack ice against the coast. The presence throughout early spring of both fast and pack ice, separated by a zone of thin ice or open water, is essential to large populations of Weddell seals, emperor penguins and whales in the area. The transect from the continent included ice pack that was undergoing early summer decay, characterized by differential expansion and melting which brought about a gradual decrease in concentration toward the ice edge.

scholarly journals Composition of population and transport of juveniles of Antarctic krill in Powell Basin region (northwestern Weddell Sea) in January 2020

Trudy VNIRO ◽  
2020 ◽  
Vol 181 ◽  
pp. 33-51
Author(s):  
V.A. Spiridonov ◽  
◽  
A.K. Zalota ◽  
V.A. Yakovenko ◽  
K.M. Gorbatenko ◽  
...  
Keyword(s):  
Antarctic Krill ◽  
Sea Water ◽  
Average Length ◽  
Size Composition ◽  
Euphausia Superba ◽  
Weddell Sea ◽  
Atlantic Sector ◽  
Bransfield Strait ◽  
The North ◽  
Average Size

This paper presents the data on distribution and size composition of the Antarctic krill (Euphausia superba) population in the northwestern Weddell Sea (Powell Basin) and adjacent areas in summer 2020. Juvenile krill dominated in the western Powell basin and the eastern Bransfield Strait as a result of transport with the advected Weddell Sea water and drifting sea ice. Using a distribution mixture analysis made possible to identify up to 9–10 size groups of krill. Groups 1–4 corresponds to juveniles (average size about 22, 25, 27–28 and 32 mm respectively). They may reflect the transport of different “waves” of recruitment of the Atlantic sector krill population with the waters of the western branch of Weddell Gyre as well as the presence of juvenile krill of local origin. Groups 5–7 are intermediate in size (average length within 38–43 mm) and include mostly immature specimens. Larger groups 8–10 comprise of mostly mature females and mature and immature males. The maximum average size of the largest group reaches about 53 mm. the Wedell Front zone in the north of Powell Basin plays an in important role for retention and growth of krill, originating from different sources: western Weddell Sea, Bransfield Strait and the zone of the southern branch of Antarctic Circumpolar Current.

INTEGRATED ALGA-CULTURE IN INUNDATED COASTAL FARMLANDS OF INDIAN SUNDARBANS AS A SUSTAINABLE ADAPTATION FOR MARGINAL COMMUNITIES TOWARDS CLIMATE RISK REDUCTION

2017 ◽  
Author(s):  
Dipayan Dey ◽  
Dipayan Dey ◽  
Ashoka Maity ◽  
Ashoka Maity
Keyword(s):  
Coastal Wetlands ◽  
Algal Growth ◽  
Open Water ◽  
Fish Bone ◽  
Algal Flora ◽  
Daily Growth Rate ◽  
Monsoon Period ◽  
Daily Growth ◽  
Culture Techniques ◽  
Tidal Waters

Algae has a great potential for quick capture of biological carbon and its storage in saltwater-inundated coastal wetlands and can also be introduced as a climate adaptive alternate farming practice. An intervention with native algal flora Enteromorpha sp. in enclosed coastal Sundarbans in India on two open water culture techniques, viz. U-Lock & Fish-Bone, shows that growth in native algal stock is influenced by seasonal variations of salinity and other limnological factors. Sundarbans, facing the odds of climate change is fast loosing arable lands to sea level rise. Algaculture in inundated coastal areas can be an adaptive mitigation for the same. Perusal of results show that daily growth rate (DGR%) increases with increasing salinity of the intruding tidal waters to an extent and biomass increment under salt stress results in accumulation of metabolites those are having nutrient values and can yield bio-diesel as well. Algal growth recorded mostly in post monsoon period, has impacts on pH and Dissolved Oxygen (DO) of the ambient water to facilitate integrated pisciculture. The paper suggests that alga-culture has unrealized potentials in carbon sequestration and can be significantly used for extraction of Biodiesel.

Observations on the Quaternary geology around Nioghalvfjerdsfjorden, eastern North Greenland

1999 ◽  
pp. 56-60
Author(s):  
Ole Bennike ◽  
Anker Weidick
Keyword(s):  
Late Summer ◽  
Open Water ◽  
Quaternary Geology ◽  
Mean Annual Precipitation ◽  
Outlet Glacier ◽  
Ice Caps ◽  
North East ◽  
Pack Ice ◽  
Lake Deposits ◽  
North Greenland

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Bennike, O., & Weidick, A. (1999). Observations on the Quaternary geology around Nioghalvfjerdsfjorden, eastern North Greenland. Geology of Greenland Survey Bulletin, 183, 56-60. https://doi.org/10.34194/ggub.v183.5205 _______________ In North and North-East Greenland, several of the outlet glaciers from the Inland Ice have long, floating tongues (Higgins 1991). Nioghalvfjerdsfjorden (Fig. 1) is today occupied by a floating outlet glacier that is about 60 km long, and the fjord is surrounded by dissected plateaux with broad valleys (Thomsen et al. 1997). The offshore shelf to the east of Nioghalvfjerdsfjorden is unusually broad, up to 300 km wide (Cherkis & Vogt 1994), and recently small low islands were discovered on the western part of this shelf (G. Budeus and T.I.H. Andersson, personal communications 1998). Quaternary deposits are widespread around Nioghalvfjerdsfjorden and include glacial, glaciofluvial, marine, deltaic and ice lake deposits. Ice margin features such as kame deposits and moraines are also common (Davies 1972). The glaciation limit increases from 200 m a.s.l. over the eastern coastal islands to 1000 m in the inland areas; local ice caps and valley glaciers are common in the region, although the mean annual precipitation is only about 200 mm per year. Most of the sea in the area is covered by permanent sea ice, with pack ice further east, but open water is present in late summer in some fjords north of Nioghalvfjerdsfjorden, and in the Nordøstvandet polynia.

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