The Genesis of the McMurdo Ice Shelf, Antarctica

Debenham, Frank

doi:10.3189/s0022143000018888

Cited by 4 publications

(4 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Considering the shallow depth (3 to 10 m) of the water samples from Michel et al (1979), a mixture of 65% east sound water with 35°7o glacial meltwater (Ross Ice Shelf or nearby glaciers; Tritium = 0.0) could indicate a similar age. Freshwater lenses indicative of glacial rather than sea ice meltwater are present in the western Sound (Debenham 1965;Gow et al 1965; this study) and may have been unwittingly sampled by Michel et al (1979). Salinity values were not reported, but would clarify the status of the water samples from beneath the Shelf.…”

Section: Discussionmentioning

confidence: 99%

Hydrographic patterns in McMurdo Sound, Antarctica and their relationship to local benthic communities

Barry

1988

Polar Biol

View full text Add to dashboard Cite

Summary. Measurements of hydrographic parameters (temperature, salinity, nitrate, nitrite, phosphate, chlorophyll a, phaeophytin, and oxygen) in McMurdo Sound, Antarctica during spring, 1984, before the regional phytoplankton bloom, and summer, 1984, after the peak of the bloom, indicate the several processes contribute to changes in the vertical and horizontal structure of the water column. Regional variation in the source of water masses within the Sound, ice cover patterns, and meltwater from the Ross Ice Shelf and nearby continental glaciers result in east-west and north-south gradients in the thermohaline, nutrient, and productivity characteristics of the Sound. These patterns are also related to the extremely variable structure and productivity of shallow water benthic macrofaunal communities in McMurdo Sound. Hydrographic patterns during Spring (November) were indicative of conditions at the end of winter prior to the spring phytoplankton bloom. The water column was nearly isothermal with temperatures near or below the surface freezing point of seawater with only a slight salinity increase with depth. Salinity was lower in the west Sound than in the east, probably in response to glacial meltwater input from the Ross Ice Shelf and/or terrestrial sources. Nutrient levels were high and nearly homogeneous throughout the Sound. Chlorophyll a was low (< 1.0 ~tg/1) throughout most of the Sound, but was lowest in the western sound, as expected from the circulation pattern (Barry and Dayton 1988). Oxygen was uniformly low during spring. The summer hydrographic distributions, estimated from samples collected during the decline of the regional plankton bloom, were dramatically different than in during spring. Both the salinity and temperature were vertically stratified at all sites, particularly in the west Sound. Temperatures near the surface were well above the freezing point and occasionally near or above 0 °C. Near surface salinity in the western Sound was nearly fresh (0.4 ppt) at some locations in the southwestern Sound. Chlorophyll a was high throughout the Sound relative to spring concentrations, and nutrient levels (NO3, PO4) were strongly depressed near the surface, due mainly to phytoplankton uptake rather than by dilution. Primary productivity estimates based on the summer nitrate and phosphate deficits over 90 days were 1.96-2.02 and 0.39-1.02 gCm-2d -1 for the east and west sound, respectively. Nutrient ratios indicated that glacial meltwater from the Ross Ice Shelf and/or nearby terrestrial sources may be an important component of the summer meltwater input to the western Sound. Enhanced water column stability due to this input may prolong the maintenance of high water column stability as this water mass flows northward and result in particularly high productivity in northern McMurdo Sound.

show abstract

Section: Discussionmentioning

confidence: 99%

Hydrographic patterns in McMurdo Sound, Antarctica and their relationship to local benthic communities

Barry

1988

Polar Biol

View full text Add to dashboard Cite

show abstract

“…Kuipers Munneke and others, 2018). The Western end of the McMIS is covered with wind-blown terrigenous debris (Glasser and others, 2006) and marine sediment derived from basal freezing and anchor ice deposition (Debenham, 1965; Swithinbank, 1970; Kellogg and Kellogg, 1987). The presence of convoluted medial moraines on the Western McMIS, suggests that the McMIS is largely a relict of a once more widespread ice shelf filling McMurdo Sound (Glasser and others, 2006).…”

Section: Field Settingmentioning

confidence: 99%

Diurnal seismicity cycle linked to subsurface melting on an ice shelf

MacAyeal

Banwell

Okal³

et al. 2018

Ann. Glaciol.

View full text Add to dashboard Cite

Seismograms acquired on the McMurdo Ice Shelf, Antarctica, during an Austral summer melt season (November 2016–January 2017) reveal a diurnal cycle of seismicity, consisting of hundreds of thousands of small ice quakes limited to a 6–12 hour period during the evening, in an area where there is substantial subsurface melting. This cycle is explained by thermally induced bending and fracture of a frozen surface superimposed on a subsurface slush/water layer that is supported by solar radiation penetration and absorption. A simple, one-dimensional model of heat transfer driven by observed surface air temperature and shortwave absorption reproduces the presence and absence (as daily weather dictated) of the observed diurnal seismicity cycle. Seismic event statistics comparing event occurrence with amplitude suggest that the events are generated in a fractured medium featuring relatively low stresses, as is consistent with a frozen surface superimposed on subsurface slush. Waveforms of the icequakes are consistent with hydroacoustic phases at frequency $ {\bf \gt} \bf 75\,{\bf Hz}$ and flexural-gravity waves at frequency $ \bf {\bf \lt}25\,{\bf Hz}$. Our results suggest that seismic observation may prove useful in monitoring subsurface melting in a manner that complements other ground-based methods as well as remote sensing.

show abstract

“…The western MIS moves very slowly as the ice inflow from grounded catchment basins or other ice shelf areas is almost completely missing [Glasser et al, 2006;Swithinbank, 1970]. It was concluded by previous authors that the strong surface ablation on the western MIS is balanced by basal freezing [Debenham, 1965;Kellogg et al, 1990]. In the east of McMurdo Sound relatively warm Antarctic surface water is drawn into the ice shelf cavity during summer causing melt at the ice shelf base .…”

Section: Introductionmentioning

confidence: 99%

Airborne thickness and freeboard measurements over the McMurdo Ice Shelf, Antarctica, and implications for ice density

Rack

Haas

Langhorne

2013

J. Geophys. Res. Oceans

View full text Add to dashboard Cite

[1] We present airborne measurements to investigate the thickness of the western McMurdo Ice Shelf in the western Ross Sea, Antarctica. Because of basal accretion of marine ice and brine intrusions conventional radar systems are limited in detecting the ice thickness in this area. In November 2009, we used a helicopter-borne laser and electromagnetic induction sounder (EM bird) to measure several thickness and freeboard profiles across the ice shelf. The maximum electromagnetically detectable ice thickness was about 55 m. Assuming hydrostatic equilibrium, the simultaneous measurement of ice freeboard and thickness was used to derive bulk ice densities ranging from 800 to 975 kg m À3 . Densities higher than those of pure ice can be largely explained by the abundance of sediments accumulated at the surface and present within the ice shelf, and are likely to a smaller extent related to the overestimation of ice thickness by the electromagnetic induction measurement related to the presence of a subice platelet layer. The equivalent thickness of debris at a density of 2800 kg m À3 is found to be up to about 2 m thick. A subice platelet layer below the ice shelf, similar to what is observed in front of the ice shelf below the sea ice, is likely to exist in areas of highest thickness. The thickness and density distribution reflects a picture of areas of basal freezing and supercooled Ice Shelf Water emerging from below the central ice shelf cavity into McMurdo Sound.Citation: Rack, W., C. Haas, and P. J. Langhorne (2013), Airborne thickness and freeboard measurements over the McMurdo Ice Shelf, Antarctica, and implications for ice density,

show abstract

The Genesis of the McMurdo Ice Shelf, Antarctica

Abstract: ABSTRACT. The recent discovery (G ow and othe rs, 1965)

Cited by 4 publications

References 2 publications

Hydrographic patterns in McMurdo Sound, Antarctica and their relationship to local benthic communities

Hydrographic patterns in McMurdo Sound, Antarctica and their relationship to local benthic communities

Diurnal seismicity cycle linked to subsurface melting on an ice shelf

Airborne thickness and freeboard measurements over the McMurdo Ice Shelf, Antarctica, and implications for ice density

Contact Info

Product

Resources

About