Biogeochemistry of platelet ice: its influence on particle flux under fast ice in the Weddell Sea, Antarctica

2002 ◽  
pp. 169-179
Author(s):  
David N. Thomas ◽  
Hilary Kennedy ◽  
Gerhard Kattner ◽  
Dieter Gerdes ◽  
G. S. Dieckmann ◽  
...  
Keyword(s):  
Particle Flux ◽  
Weddell Sea ◽  
Fast Ice ◽  
Platelet Ice

Biogeochemistry of platelet ice: its influence on particle flux under fast ice in the Weddell Sea, Antarctica

Polar Biology ◽  
2001 ◽  
Vol 24 (7) ◽  
pp. 486-496 ◽  
Author(s):  
David Thomas ◽  
Hilary Kennedy ◽  
Gerhard Kattner ◽  
Dieter Gerdes ◽  
Carl Gough ◽  
...  
Keyword(s):  
Particle Flux ◽  
Weddell Sea ◽  
Fast Ice ◽  
Platelet Ice

Seasonal development of algal biomass in snow-covered fast ice and the underlying platelet layer in the Weddell Sea, Antarctica

1999 ◽  
Vol 11 (3) ◽  
pp. 305-315 ◽  
Author(s):  
Sven Günther ◽  
Gerhard S. Dieckmann
Keyword(s):  
Sea Ice ◽  
Snow Cover ◽  
Ross Sea ◽  
Early Spring ◽  
Weddell Sea ◽  
Seasonal Development ◽  
Algal Communities ◽  
Ice Growth ◽  
Fast Ice ◽  
Platelet Ice

The seasonal changes of the nutrient regime and the development of algal communities in snow-covered fast ice and the underlying platelet layer was investigated in the eastern Weddell Sea during autumn, winter, and spring 1995. In the upper sea ice, an autumnal diatom community became enclosed during subsequent ice growth in winter, declined, and was replaced by a flagellate dominated community in spring. In this layer, nitrate was completely exhausted at the end of spring, although nutrients had been partly regenerated in early spring. The progressive congelation of platelet ice contributed significantly to sea ice growth thus influencing algal inoculation of the sea ice bottom. Biomass, present in the uppermost section of the platelet layer, could be found in the sea ice bottom after this section congealed to solid ice. After incorporation, species composition changed from larger and chain-forming species to species of smaller cell size. Concurrently, net growth rate slowed down from 0.07 day−1 within the platelet layer to 0.03 day−1 within the sea ice. Despite a thick snow cover of more than 20 cm, maximum biomass yield was 210 mg chl a m−2 in the platelet layer and 40 mg chl a m−2 in the sea ice respectively, while 95% of the latter was located within consolidated platelet ice. Total fast ice biomass observed here is significantly lower than that observed in snow-free fast ice of the Ross Sea, but because snow cover of the southern Weddell Sea is representative of most fast ice areas in the Antarctic, the data presented here are of general value.

Thraustochytrid protists in Antarctic fast ice?

1993 ◽  
Vol 5 (3) ◽  
pp. 279-280 ◽  
Author(s):  
Franz Riemann ◽  
Karsten Schaumann
Keyword(s):  
Sea Ice ◽  
Ice Core ◽  
Short Note ◽  
Weddell Sea ◽  
Lower Section ◽  
Fast Ice ◽  
Arctic Ice ◽  
Pennate Diatoms

Sea ice provides a habitat for a conspicuous and productive assemblage of autotrophic microalgae and for heterotrophs ranging from bacteria to vertebrates (Horner 1990, Garrison 1991). With the exception of a reference to chytridiaceous fungi that were found infecting Arctic ice diatoms (Horner 1977) and a note in a cruise report (Schnack-Schiel 1987, p. 153), it appears that fungi and similar organisms have until now not been mentioned as members of the heterotrophic sea ice community. In the present short note we report on the abundant occurrence of apparently thraustochytrid fungus-like protists associated with mucilage tubes of pennate diatoms, encountered in the lower section of a fast ice core drilled close to the southern shelf ice margin of the Weddell Sea.

scholarly journals Turbulent heat transfer as a control of platelet ice growth in supercooled under-ice ocean boundary layers

Ocean Science ◽  
2016 ◽  
Vol 12 (2) ◽  
pp. 507-515 ◽  
Author(s):  
Miles G. McPhee ◽  
Craig L. Stevens ◽  
Inga J. Smith ◽  
Natalie J. Robinson
Keyword(s):  
Heat Transfer ◽  
Sea Ice ◽  
Turbulent Heat Transfer ◽  
Late Winter ◽  
Turbulent Heat ◽  
Ice Shelves ◽  
Ice Growth ◽  
Turbulent Heat Exchange ◽  
Fast Ice ◽  
Platelet Ice

Abstract. Late winter measurements of turbulent quantities in tidally modulated flow under land-fast sea ice near the Erebus Glacier Tongue, McMurdo Sound, Antarctica, identified processes that influence growth at the interface of an ice surface in contact with supercooled seawater. The data show that turbulent heat exchange at the ocean–ice boundary is characterized by the product of friction velocity and (negative) water temperature departure from freezing, analogous to similar results for moderate melting rates in seawater above freezing. Platelet ice growth appears to increase the hydraulic roughness (drag) of fast ice compared with undeformed fast ice without platelets. Platelet growth in supercooled water under thick ice appears to be rate-limited by turbulent heat transfer and that this is a significant factor to be considered in mass transfer at the underside of ice shelves and sea ice in the vicinity of ice shelves.

scholarly journals Structural characteristics of congelation and platelet ice and their role in the development of antarctic land-fast sea ice

1993 ◽  
Vol 39 (132) ◽  
pp. 223-238 ◽  
Author(s):  
M. O. Jeffries ◽  
W. F. Weeks ◽  
R. Shaw ◽  
K. Morris
Keyword(s):  
Growth Rates ◽  
Ice Cores ◽  
Current Control ◽  
Water Current ◽  
Minor Amount ◽  
Mcmurdo Sound ◽  
Ice Growth ◽  
Fast Ice ◽  
Ice Fabrics ◽  
Platelet Ice

AbstractIce cores were obtained in January 1990 from the land-fast ice in McMurdo Sound for a study of variations in texture, fabric, sub-structure, composition and development. Two primary ice types were observed, congelation and platelet, with a minor amount of frazil ice. Congelation ice growth precedes platelet-ice accretion. Congelation-ice fabrics show frequent moderate to strong alignments, a phenomenon believed to be due to water-current control of selective ice-crystal growth. Platelet ice originates at the base of the congelation ice, initially as a porous latticework of tabular ice crystals which subsequently consolidate by congelation of the interstitial water. Interstitial congelation-ice fabrics generally have little or no alignment, indicating the reduced effect of currents within the platelet latticework prior to solidification. Platelet-crystal textures range from small, wavy-edged forms to large, blade-like forms. Platelet-crystal fabrics indicate that, in addition to being randomly oriented, the platelet latticeworks commonly include many crystals with their flat (0001) faces oriented both parallel and normal to the base of the overlying ice. Plate-width data suggest that the interstitial congelation ice-growth rates remain similar to those of the overlying congelation ice. This effective increase in growth rates probably happens because the latticework of accumulating platelets ahead of the freezing interface ensures that the water within the platelet layer is at the freezing point and less heat has to be removed from platelet-rich water than from platelet-free water for a given thickness of congelation ice to grow. The negative oceanic heat flux associated with platelet-ice formation in McMurdo Sound explains why McMurdo Sound fast ice is thicker than Ross Sea pack ice, and also why it reaches a greater thickness than Arctic fast ice grown in a similar polar marine climate. Plate widths in the McMurdo Sound congelation ice suggest, however, that it grows no faster than Arctic congelation ice.

Seasonal variability of particle flux in the Weddell Sea and its relation to ice cover

Nature ◽  
1988 ◽  
Vol 335 (6189) ◽  
pp. 426-428 ◽  
Author(s):  
Gerhard Fischer ◽  
Dieter Fütterer ◽  
Rainer Gersonde ◽  
Susumu Honjo ◽  
Dorinda Ostermann ◽  
...  
Keyword(s):  
Seasonal Variability ◽  
Particle Flux ◽  
Ice Cover ◽  
Weddell Sea

scholarly journals Ice platelets below Weddell Sea landfast sea ice

2015 ◽  
Vol 56 (69) ◽  
pp. 175-190 ◽  
Author(s):  
Mario Hoppmann ◽  
Marcel Nicolaus ◽  
Stephan Paul ◽  
Priska A. Hunkeler ◽  
Günther Heinemann ◽  
...  
Keyword(s):  
Sea Ice ◽  
Volume Fraction ◽  
Weddell Sea ◽  
Ice Shelf ◽  
Platelet Volume ◽  
Local Maxima ◽  
Model Studies ◽  
Warm Surface Water ◽  
Fast Ice ◽  
Landfast Sea Ice

AbstractBasal melt of ice shelves may lead to an accumulation of disc-shaped ice platelets underneath nearby sea ice, to form a sub-ice platelet layer. Here we present the seasonal cycle of sea ice attached to the Ekström Ice Shelf, Antarctica, and the underlying platelet layer in 2012. Ice platelets emerged from the cavity and interacted with the fast-ice cover of Atka Bay as early as June. Episodic accumulations throughout winter and spring led to an average platelet-layer thickness of 4 m by December 2012, with local maxima of up to 10 m. The additional buoyancy partly prevented surface flooding and snow-ice formation, despite a thick snow cover. Subsequent thinning of the platelet layer from December onwards was associated with an inflow of warm surface water. The combination of model studies with observed fast-ice thickness revealed an average ice-volume fraction in the platelet layer of 0.25 ± 0.1. We found that nearly half of the combined solid sea-ice and ice-platelet volume in this area is generated by heat transfer to the ocean rather than to the atmosphere. The total ice-platelet volume underlying Atka Bay fast ice was equivalent to more than one-fifth of the annual basal melt volume under the Ekström Ice Shelf.

scholarly journals Structural characteristics of congelation and platelet ice and their role in the development of antarctic land-fast sea ice

1993 ◽  
Vol 39 (132) ◽  
pp. 223-238 ◽  
Author(s):  
M. O. Jeffries ◽  
W. F. Weeks ◽  
R. Shaw ◽  
K. Morris
Keyword(s):  
Growth Rates ◽  
Ice Cores ◽  
Current Control ◽  
Water Current ◽  
Minor Amount ◽  
Mcmurdo Sound ◽  
Ice Growth ◽  
Fast Ice ◽  
Ice Fabrics ◽  
Platelet Ice

AbstractIce cores were obtained in January 1990 from the land-fast ice in McMurdo Sound for a study of variations in texture, fabric, sub-structure, composition and development. Two primary ice types were observed, congelation and platelet, with a minor amount of frazil ice. Congelation ice growth precedes platelet-ice accretion. Congelation-ice fabrics show frequent moderate to strong alignments, a phenomenon believed to be due to water-current control of selective ice-crystal growth. Platelet ice originates at the base of the congelation ice, initially as a porous latticework of tabular ice crystals which subsequently consolidate by congelation of the interstitial water. Interstitial congelation-ice fabrics generally have little or no alignment, indicating the reduced effect of currents within the platelet latticework prior to solidification. Platelet-crystal textures range from small, wavy-edged forms to large, blade-like forms. Platelet-crystal fabrics indicate that, in addition to being randomly oriented, the platelet latticeworks commonly include many crystals with their flat (0001) faces oriented both parallel and normal to the base of the overlying ice. Plate-width data suggest that the interstitial congelation ice-growth rates remain similar to those of the overlying congelation ice. This effective increase in growth rates probably happens because the latticework of accumulating platelets ahead of the freezing interface ensures that the water within the platelet layer is at the freezing point and less heat has to be removed from platelet-rich water than from platelet-free water for a given thickness of congelation ice to grow. The negative oceanic heat flux associated with platelet-ice formation in McMurdo Sound explains why McMurdo Sound fast ice is thicker than Ross Sea pack ice, and also why it reaches a greater thickness than Arctic fast ice grown in a similar polar marine climate. Plate widths in the McMurdo Sound congelation ice suggest, however, that it grows no faster than Arctic congelation ice.

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