Ocean heat flux under Antarctic sea ice in the Bellingshausen and Amundsen Seas: two case studies

AbstractWe examine the role of ocean heat flux (OHF) in Antarctic sea-ice growth and melt using data from autonomous ice mass-balance buoys deployed on pack ice in the Bellingshausen Sea and on fast ice in the Amundsen Sea during the spring/summer (October-December 2007) and summer/ autumn (February-March 2009) transitions, respectively. OHFs are derived using two methods that examine changes in (1) sub-ice ocean water properties (OHF1) and (2) ice thickness (OHF2), the latter only applying to thick snow-covered ice (i.e. a near-zero temperature gradient near the ice bottom). Good agreement is found between the time-averaged estimates of OHF1 and OHF2. Average OHF measured was 8 ± 2 W m-2 under the pack ice and 17 ± 2 W m-2 under the landfast ice. Some short-term OHF values (OHF1) in both seas exceeded 55 W m-2. The spring OHF variations in the Bellingshausen Sea were periodic and controlled by semi-diurnal ice velocity fluctuations. Larger temperature fluctuations in the summer Amundsen Sea, originating from incursions of warm deep water masses, contributed to the OHF being twice as high as in the Bellingshausen Sea and also accounted for the irregular OHF variability there.

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The importance of wind-blown snow redistribution to snow accumulation on Bellingshausen Sea ice

Annals of Glaciology ◽

10.3189/172756411795931651 ◽

2011 ◽

Vol 52 (57) ◽

pp. 271-278 ◽

Cited By ~ 31

Author(s):

Katherine C. Leonard ◽

Ted Maksym

Keyword(s):

Sea Ice ◽

Mass Balance ◽

Snow Accumulation ◽

Blowing Snow ◽

Wind Speeds ◽

Antarctic Sea Ice ◽

Drifting Snow ◽

Bellingshausen Sea ◽

Ice Mass Balance ◽

High Winds

AbstractSnow distribution is a dominating factor in sea-ice mass balance in the Bellingshausen Sea, Antarctica, through its roles in insulating the ice and contributing to snow-ice production. the wind has long been qualitatively recognized to influence the distribution of snow accumulation on sea ice, but the relative importance of drifting and blowing snow has not been quantified over Antarctic sea ice prior to this study. the presence and magnitude of drifting snow were monitored continuously along with wind speeds at two sites on an ice floe in the Bellingshausen Sea during the October 2007 Sea Ice Mass Balance in the Antarctic (SIMBA) experiment. Contemporaneous precipitation measurements collected on board the RVIB Nathaniel B. Palmer and accumulation measurements by automated ice mass-balance buoys (IMBs) allow us to document the proportion of snowfall that accumulated on level ice surfaces in the presence of high winds and blowing-snow conditions. Accumulation on the sea ice during the experiment averaged <0.01 m w.e. at both IMB sites, during a period when European Centre for Medium-Range Weather Forecasts analyses predicted >0.03 m w.e. of precipitation on the ice floe. Accumulation changes on the ice floe were clearly associated with drifting snow and high winds. Drifting-snow transport during the SIMBA experiment was supply-limited. Using these results to inform a preliminary study using a blowing-snow model, we show that over the entire Southern Ocean approximately half of the precipitation over sea ice could be lost to leads.

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Physical and Structural Characteristics of Antarctic Sea Ice

Annals of Glaciology ◽

10.3189/s0260305500002627 ◽

1982 ◽

Vol 3 ◽

pp. 113-117 ◽

Cited By ~ 16

Author(s):

A.J. Gow ◽

S.F. Ackley ◽

W.F. Weeks ◽

J.W. Govoni

Keyword(s):

Sea Ice ◽

Structural Characteristics ◽

Weddell Sea ◽

The Arctic ◽

Mcmurdo Sound ◽

Frazil Ice ◽

Antarctic Sea Ice ◽

Pack Ice ◽

Fast Ice ◽

Ice Production

Observations during February and March 1980 of structures in 66 separate floes in Weddell Sea pack ice show widespread occurrence of frazil ice in amounts not previously reported in sea ice of comparable age and thickness in the Arctic. It is estimated that as much as 50% of the total ice production in the Weddell Sea is generated as frazil. Average floe salinities also appear higher than those of their Arctic counterparts. Comparative studies of fast ice at 28 locations in McMurdo Sound show this ice to be composed almost entirely of congelation ice that exhibits crystalline textures and orientations that are similar to those observed in Arctic fast ice. However, average fast-ice salinities in McMurdo Sound are higher than those reported for Arctic fast ice of comparable age and thickness.

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Physical and Structural Characteristics of Antarctic Sea Ice

Annals of Glaciology ◽

10.1017/s0260305500002627 ◽

1982 ◽

Vol 3 ◽

pp. 113-117 ◽

Cited By ~ 78

Author(s):

A.J. Gow ◽

S.F. Ackley ◽

W.F. Weeks ◽

J.W. Govoni

Keyword(s):

Sea Ice ◽

Structural Characteristics ◽

Weddell Sea ◽

The Arctic ◽

Mcmurdo Sound ◽

Frazil Ice ◽

Antarctic Sea Ice ◽

Pack Ice ◽

Fast Ice ◽

Ice Production

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Snow-ice contribution to the structure of sea ice in the Amundsen Sea, Antarctica

Annals of Glaciology ◽

10.1017/aog.2020.55 ◽

2020 ◽

pp. 1-10

Author(s):

Lijun Tian ◽

Yongli Gao ◽

Blake Weissling ◽

Stephen F. Ackley

Keyword(s):

Sea Ice ◽

Meteoric Water ◽

Diffusion Processes ◽

Isotope Composition ◽

Critical Role ◽

Ice Cores ◽

Mixing Model ◽

Amundsen Sea ◽

Antarctic Sea Ice ◽

Pack Ice

Abstract The widespread occurrence of snow-ice formation on the pack ice plays a critical role in the mass balance of Antarctic sea ice. The stable isotope composition, ice texture and salinity of eight ice cores, obtained from the Amundsen Sea during the Oden Southern Ocean 2010/11 expedition from late December 2010 to January 2011, were investigated to illustrate the snow-ice growth process and its contribution to sea-ice development. Most previous research has utilized δ18O as an index tracer to determine the percentages of core length that contain meteoric water, i.e. snow ice. However, this standard practice of snow-ice identification might be biased due to normally low-resolution isotopic measurements and mixing/diffusion processes between the snow ice and underlying ice layers. Snow-ice contributions in these ice cores based instead on an updated isotope mixing model are also presented. Depth profiles of ice texture and salinity are described to serve as representations of the structures of these ice cores. Our isotope mixing model produced an average of 15.9% snow-ice contribution for pack ice in the Amundsen Sea, and meteoric water occupying 40% of snow-ice mass for all ice stations. These results are compared to previous investigations of snow-ice occurrence around Antarctica.

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East Antarctic sea ice: observations and modelling

Annals of Glaciology ◽

10.3189/1998aog27-1-427-432 ◽

1998 ◽

Vol 27 ◽

pp. 427-432 ◽

Cited By ~ 5

Author(s):

Anthony P. Worby ◽

Xingren Wu

Keyword(s):

Sea Ice ◽

Climate Models ◽

Numerical Models ◽

Global Climate ◽

Thickness Distribution ◽

Ice Thickness ◽

Antarctic Sea Ice ◽

Pack Ice ◽

Concentration Sensitivity ◽

Sensitivity Studies

The importance of monitoring sea ice for studies of global climate has been well noted for several decades. Observations have shown that sea ice exhibits large seasonal variability in extent, concentration and thickness. These changes have a significant impact on climate, and the potential nature of many of these connections has been revealed in studies with numerical models. An accurate representation of the sea-ice distribution (including ice extent, concentration and thickness) in climate models is therefore important for modelling global climate change. This work presents an overview of the observed sea-ice characteristics in the East Antarctic pack ice (60-150° E) and outlines possible improvements to the simulation of sea ice over this region by modifying the ice-thickness parameterisation in a coupled sea-ice-atmosphere model, using observational data of ice thickness and concentration. Sensitivity studies indicate that the simulation of East Antarctic sea ice can be improved by modifying both the “lead parameterisation” and “rafting scheme” to be ice-thickness dependent. The modelled results are currently out of phase with the observed data, and the addition of a multilevel ice-thickness distribution would improve the simulation significantly.

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Low Salinity and High-Level UV-B Radiation Reduce Single-Cell Activity in Antarctic Sea Ice Bacteria

Applied and Environmental Microbiology ◽

10.1128/aem.00829-09 ◽

2009 ◽

Vol 75 (23) ◽

pp. 7570-7573 ◽

Cited By ~ 13

Author(s):

Andrew Martin ◽

Julie Hall ◽

Ken Ryan

Keyword(s):

Sea Ice ◽

Metabolic Activity ◽

Cell Activity ◽

Ice Formation ◽

Freeze Thaw ◽

Low Salinity ◽

Antarctic Sea Ice ◽

Single Cell Activity ◽

Fast Ice ◽

High Level

ABSTRACT Experiments simulating the sea ice cycle were conducted by exposing microbes from Antarctic fast ice to saline and irradiance regimens associated with the freeze-thaw process. In contrast to hypersaline conditions (ice formation), the simulated release of bacteria into hyposaline seawater combined with rapid exposure to increased UV-B radiation significantly reduced metabolic activity.

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Albedo of the ice covered Weddell and Bellingshausen Seas

The Cryosphere ◽

10.5194/tc-6-479-2012 ◽

2012 ◽

Vol 6 (2) ◽

pp. 479-491 ◽

Cited By ~ 9

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.

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Estimating the thickness of ridged sea ice from ship observations in the Ross Sea

Antarctic Science ◽

10.1017/s0954102003001056 ◽

2003 ◽

Vol 15 (1) ◽

pp. 47-54 ◽

Cited By ~ 5

Author(s):

TINA TIN ◽

MARTIN O. JEFFRIES ◽

MIKKO LENSU ◽

JUKKA TUHKURI

Keyword(s):

Sea Ice ◽

Ross Sea ◽

Low Cost ◽

Thickness Distribution ◽

Ice Thickness ◽

Equivalent Thickness ◽

Sea Ice Thickness ◽

Antarctic Sea Ice ◽

Using Data ◽

Original Formula

Ship-based observations of sea ice thickness using the Antarctic Sea Ice Processes and Climate (ASPeCt) protocol provide information on ice thickness distribution at relatively low cost. This protocol uses a simple formula to calculate the mass of ice in ridges based on surface observations. We present two new formulae and compare these with results from the “Original” formula using data obtained in the Ross Sea in autumn and winter. The new “r-star” formula uses a more realistic ratio of sail and keel areas to transform dimensions of sails to estimates of mean keel areas. As a result, estimates of “equivalent thickness” (i.e. mean thickness of ice in ridged areas) increased by over 200%. The new “Probability” formula goes one step further, by incorporating the probability that a sail is associated with a keel underwater, and the probability that keels may be found under level surfaces. This resulted in estimates of equivalent thickness comparable with the Original formula. Estimates of equivalent thickness at one or two degree latitude resolution are sufficiently accurate for validating sea ice models. Although ridges are small features in the Ross Sea, we have shown that they constitute a significant fraction of the total ice mass.

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Tropical Pacific SST Drivers of Recent Antarctic Sea Ice Trends

Journal of Climate ◽

10.1175/jcli-d-16-0440.1 ◽

2016 ◽

Vol 29 (24) ◽

pp. 8931-8948 ◽

Cited By ~ 31

Author(s):

Ariaan Purich ◽

Matthew H. England ◽

Wenju Cai ◽

Yoshimitsu Chikamoto ◽

Axel Timmermann ◽

...

Keyword(s):

Sea Ice ◽

Climate Models ◽

Climate Model ◽

Ross Sea ◽

Surface Wind ◽

Tropical Pacific ◽

Sea Ice Concentration ◽

Amundsen Sea ◽

Model Simulations ◽

Antarctic Sea Ice

Abstract A strengthening of the Amundsen Sea low from 1979 to 2013 has been shown to largely explain the observed increase in Antarctic sea ice concentration in the eastern Ross Sea and decrease in the Bellingshausen Sea. Here it is shown that while these changes are not generally seen in freely running coupled climate model simulations, they are reproduced in simulations of two independent coupled climate models: one constrained by observed sea surface temperature anomalies in the tropical Pacific and the other by observed surface wind stress in the tropics. This analysis confirms previous results and strengthens the conclusion that the phase change in the interdecadal Pacific oscillation from positive to negative over 1979–2013 contributed to the observed strengthening of the Amundsen Sea low and the associated pattern of Antarctic sea ice change during this period. New support for this conclusion is provided by simulated trends in spatial patterns of sea ice concentrations that are similar to those observed. These results highlight the importance of accounting for teleconnections from low to high latitudes in both model simulations and observations of Antarctic sea ice variability and change.

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Preliminary evidence for the microbial loop in Antarctic sea ice using microcosm simulations

Antarctic Science ◽

10.1017/s0954102012000491 ◽

2012 ◽

Vol 24 (6) ◽

pp. 547-553 ◽

Cited By ~ 5

Author(s):

Andrew Martin ◽

Andrew McMinn ◽

Simon K. Davy ◽

Marti J. Anderson ◽

Hilary C. Miller ◽

...

Keyword(s):

Community Structure ◽

Sea Ice ◽

Metabolic Activity ◽

Bacterial Growth ◽

Denaturing Gradient Gel Electrophoresis ◽

Preliminary Evidence ◽

Antarctic Sea Ice ◽

Cell Counts ◽

Gradient Gel Electrophoresis ◽

Fast Ice

AbstractSea ice microalgae actively contribute to the pool of dissolved organic matter (DOM) available for bacterial metabolism, but this link has historically relied on bulk correlations between chlorophylla(a surrogate for algal biomass) and bacterial abundance. We incubated microbes from both the bottom (congelation layer) and surface brine region of Antarctic fast ice for nine days. Algal-derived DOM was manipulated by varying the duration of irradiance, restricting photosynthesis with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) or incubating in the dark. The bacterial response to changes in DOM availability was examined by performing cell counts, quantifying bacterial metabolic activity and examining community composition with denaturing gradient gel electrophoresis. The percentage of metabolically active bacteria was relatively low in the surface brine microcosm (10–20% of the bacterial community), the treatment with DCMU indirectly restricted bacterial growth and there was some evidence for changes in community structure. Metabolic activity was higher (35–69%) in the bottom ice microcosm, and while there was no variation in community structure, bacterial growth was restricted in the treatment with DCMU compared to the light/dark treatment. These results are considered preliminary, but provide a useful illustration of sea ice microbial dynamics beyond the use of ‘snapshot’ biomass correlations.

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