Winter Measurements of Sea Currents in McMurdo Sound

Gilmour, A. E.; Macdonald, W. J. P.; Hoeven, Frans G. Van der

doi:10.1080/00288306.1962.10417637

Cited by 25 publications

(15 citation statements)

References 5 publications

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“…Hence the mean near-surface current was found to flow toward the north at Site A. These data in general agree with the current pattern identified by previous oceanographic studies conducted in McMurdo Sound [Gilmour et al, 1960[Gilmour et al, , 1962Tressler and Ommundsen, 1962;Littlepage, 1965;Heath, 1971;Lewis and Perkin, 1985;Barry and Dayton, 1988;Robinson, 2004].…”

Section: Oceanographic Measurements 421 Winter-long Near-surface Ssupporting

confidence: 90%

Observations of platelet ice growth and oceanographic conditions during the winter of 2003 in McMurdo Sound, Antarctica

et al. 2006

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[1] Platelet ice is the name given to ice crystals that nucleate in the ocean and grow either at depth or loosely attached to the ice-water interface. Related to the proximity of ice shelves, it is known to form in supercooled seawater. This study details the conditions for its growth during the austral winter of 2003 in McMurdo Sound, Antarctica. A key finding is that the presence of platelet ice in the sea ice cover is conclusively linked to the time history of the appearance of ice crystals in the water column, monitored using the strength of the backscattered signal from an acoustic Doppler current profiler as a proxy. Generally, these crystals appeared from mid-May as water near the interface became supercooled. This near-surface supercooling appears to be related to a simultaneous, abrupt change in the structure of the upper 250 m of the water column, from one that behaved dynamically and contained both the warmest and coolest measured temperatures to one in which the water was essentially isothermal near its surface freezing temperature. Near-surface ocean temperature was also affected by tidal mixing and by an increase in the thickness and density, over the course of winter, of the surface mixed layer created by salt rejection during ice growth. These processes allowed cold water, trapped by buoyancy in a band at the base of the mixed layer in early winter, to gain access to the ice-water interface by midwinter. This band of cold water probably had its origin beneath the McMurdo Ice Shelf.

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Section: Oceanographic Measurements 421 Winter-long Near-surface Ssupporting

confidence: 90%

Observations of platelet ice growth and oceanographic conditions during the winter of 2003 in McMurdo Sound, Antarctica

et al. 2006

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“…This may be misleading, however, because temporal changes in F at time scales less than a few days in length were not investigated. It is conceivable, and perhaps likely, that diel variations in the tidally induced, current fields (Gilmour et al 1960, Gilmour et al 1962, Heath 1977, Lewis & Perkin 1985 may result in large changes in l-throughout the day which were not measured in this study. If so, considering the potential for large daily fluctuations in T, it is surprising that the apparent fortnightly pattern to the varlation in r was observed at all.…”

Section: Discussionmentioning

confidence: 68%

High resolution study of the platelet ice ecosystem in McMurdo Sound, Antarctica:biomass, nutrient, and production profiles within a dense microalgal bloom

Arrigo¹,

Dieckmann²,

Gosselin³

et al. 1995

Mar. Ecol. Prog. Ser.

102

119

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ABSTRACT-Vertical distributions of inorganic nutrients (nitrate, nitrite, ammonium, phosphate, and silicic acid) and microalgal and bacterial biomass were monitored within both the lower congelation ice and the platelet ice layer in McMurdo Sound, Antarctica from 31 October to 3 December 1989. Profiles of dissolved organic matter (DOM) (amino acids and simple sugars) and heterotrophic protists were also obtained in early December. Microalgal standing crop increased from 9.4 to 37.4 g C m-' during our 34 d study (peak accumulation rate of > l g C m-2 d-'), and maximum pigment concentrations exceeded 6500 mg chl a m-3 near the congelation ice/platelet ice interface. Estimates of seawater exchange within the platelet ice ranged from 0.06 to 0.61 m2 d-' when Si(OH), was used as a tracer. The biochemical composition of the autotrophic community and the presence of high nutrient concentrations within the platelet layer indicated that the growth of platelet ice algae was limited by l~ght, rather than nutrients, throughout the season. NO3 and Si(OH), concentrations in the platelet ice were generally high (30 to 32 and 65 to 82 mm01 m-3, respectively), but became depleted in the uppermost layers as chl a peaked late in November. NH, was far more abundant in the platelet ice (5 to 10 mm01 m-3) than in the underlying water column (0.5 mm01 m-3) throughout the field season. Microbial regeneration was primarily responsible for the high background concentrations of NH, in the platelet ice, although physical processes also may have contributed. A large NH4 pulse (>l50 mm01 m-3) was observed in the platelet layer in early November, possibly attributable to an isolated macrozooplankton grazing and excretion event. PO, concentrations (2.0 mm01 m-3 in the water column) were minimal ( < l . ? mm01 m-3) in the upper platelet ice on November 11, but began to increase thereafter due to PO, regeneration. By early December, concentrations reached their maximum of 3.73 mm01Rates of POq regeneration were highest (peak of 35 mm01 m-3 d-') in the upper layers of the platelet ice where the bulk of the microbial biomass was located. The platelet ice was unusual because, although concentrations of regenerated nutrients were often high, the elemental composition of particulates remained near the Redfield ratios and detrital abundance was low. The coincidence of NO2 and NO, peaks at a depth of 0.65 to 0.75 m suggests that bacterial nitrification may also occur in the platelet ice.

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“…Sound have indicated diurnal periodicity in current speed and/or direction (Gilmour et al 1960(Gilmour et al , 1962Tressler and Ommundsen 1962;Littlepage 1965;Heath 1977;Raytheon Service Company 1983;Lewis and Perkin 1985) which are closely associated with tidal height observations from McMurdo Sound (Heath 1977;Raytheon Service Company 1983) or from the Ross Ice Shelf (Thiel et al 1960;Williams and Robinson 1979). Tidal currents are controlled directly by equilibrium tidal motion and perhaps by tidally-induced flexing of the Ross Ice Shelf (Holdsworth 1977;Doake 1978;MacAyeal 1984), which may accentuate or damp local currents.…”

Section: Periodic Flow Most Current Observations From Mcmurdomentioning

confidence: 97%

Current patterns in McMurdo Sound, Antarctica and their relationship to local biotic communities

1988

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Winter Measurements of Sea Currents in McMurdo Sound

Cited by 25 publications

References 5 publications

Observations of platelet ice growth and oceanographic conditions during the winter of 2003 in McMurdo Sound, Antarctica

Observations of platelet ice growth and oceanographic conditions during the winter of 2003 in McMurdo Sound, Antarctica

High resolution study of the platelet ice ecosystem in McMurdo Sound, Antarctica:biomass, nutrient, and production profiles within a dense microalgal bloom

Current patterns in McMurdo Sound, Antarctica and their relationship to local biotic communities

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