A field and numerical study of the evolution of sea-ice thickness in the Ross Sea, Antarctica, 1998-99

AbstractDuring two cruises in 1998 and 1999, we examined drift and ridging characteristics of sea ice in the Ross Sea, Antarctica. Mean ice thickness in the western Ross Sea in autumn was 0.5 m, while higher level-ice thicknesses, greater areal coverages of ridges and higher sails were found in the central and eastern Ross Sea in summer. Near the continent, ice drifted westward near the coast and turned eastward further north. We use a regional sea-ice−mixed-layer−pycnocline model to initiate backward trajectories at the time and location of field observations and examine the dynamic and thermodynamic processes that determine ice thickness along these trajectories. Model results agree with previously published field data to indicate that thermodynamic and dynamic thickening and snow-ice formation each contribute significantly to the ice mass of the summer ice field in the central and eastern Ross Sea. For first-year ice in the western Ross Sea, model results and field data both indicate that thermodynamic thickening is the dominant process that determines ice thickness, with dynamic thickening also contributing 20% to the net ice-thickening rate. However, model results fail to reproduce the prevalence of snow- ice formation that was seen in field data.

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Sea ice deformation and thickness in the Western Ross Sea

10.5194/egusphere-egu21-10607 ◽

2021 ◽

Author(s):

Wolfgang Rack ◽

Daniel Price ◽

Christian Haas ◽

Patricia J. Langhorne ◽

Greg H. Leonard

Keyword(s):

Sea Ice ◽

Satellite Images ◽

Ross Sea ◽

Thickness Distribution ◽

Ice Thickness ◽

Ice Dynamics ◽

Sea Ice Thickness ◽

Ice Volume ◽

Terra Nova Bay ◽

Western Ross Sea

Sea ice cover is arguably the longest and best observed climate variable from space, with over four decades of highly reliable daily records of extent in both hemispheres. In Antarctica, a slight positive decadal trend in sea ice cover is driven by changes in the western Ross Sea, where a variation in weather patterns over the wider region forced a change in meridional winds. The distinguishing wind driven sea ice process in the western Ross Sea is the regular occurrence of the Ross Sea, McMurdo Sound, and Terra Nova Bay polynyas. Trends in sea ice volume and mass in this area unknown, because ice thickness and dynamics are particularly hard to measure.Here we present the first comprehensive and direct assessment of large-scale sea-ice thickness distribution in the western Ross Sea. Using an airborne electromagnetic induction (AEM) ice thickness sensor towed by a fixed wing aircraft (Basler BT-67), we observed in November 2017 over a distance of 800 km significantly thicker ice than expected from thermodynamic growth alone. By means of time series of satellite images and wind data we relate the observed thickness distribution to satellite derived ice dynamics and wind data. Strong southerly winds with speeds of up to 25 ms-1 in early October deformed the pack ice, which was surveyed more than a month later.We found strongly deformed ice with a mean and maximum thickness of 2.0 and 15.6 m, respectively. Sea-ice thickness gradients are highest within 100-200 km of polynyas, where the mean thickness of the thickest 10% of ice is 7.6 m. From comparison with aerial photographs and satellite images we conclude that ice preferentially grows in deformational ridges; about 43% of the sea ice volume in the area between McMurdo Sound and Terra Nova Bay is concentrated in more than 3 m thick ridges which cover about 15% of the surveyed area. Overall, 80% of the ice was found to be heavily deformed and concentrated in ridges up to 11.8 m thick.Our observations hold a link between wind driven ice dynamics and the ice mass exported from the western Ross Sea. The sea ice statistics highlighted in this contribution forms a basis for improved satellite derived mass balance assessments and the evaluation of sea ice simulations.

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Sea Ice Thickness in the Western Ross Sea

Geophysical Research Letters ◽

10.1029/2020gl090866 ◽

2020 ◽

Author(s):

Wolfgang Rack ◽

Daniel Price ◽

Christian Haas ◽

Patricia J. Langhorne ◽

Greg H. Leonard

Keyword(s):

Sea Ice ◽

Ross Sea ◽

Ice Thickness ◽

Sea Ice Thickness ◽

Western Ross Sea

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Characteristics of Sea-ice thickness and Snow-depth distributions of the Summer landfast ice in Lützow-Holm Bay, East Antarctica

Annals of Glaciology ◽

10.3189/172756406781811240 ◽

2006 ◽

Vol 44 ◽

pp. 281-287 ◽

Cited By ~ 9

Author(s):

Shotaro Uto ◽

Haruhito Shimoda ◽

Shuki Ushio

Keyword(s):

Sea Ice ◽

Interannual Variability ◽

Snow Depth ◽

East Antarctica ◽

Ice Thickness ◽

First Year ◽

Total Thickness ◽

Sea Ice Thickness ◽

Landfast Ice ◽

Northeasterly Wind

AbstractSea-ice observations have been conducted on board icebreaker shirase as a part of the Scientific programs of the Japanese Antarctic Research Expedition. We Summarize these to investigate Spatial and interannual variability of ice thickness and Snow depth of the Summer landfast ice in Lützow-Holm Bay, East Antarctica. Electromagnetic–inductive observations, which have been conducted Since 2000, provide total thickness distributions with high Spatial resolution. A clear discontinuity, which Separates thin first-year ice from thick multi-year ice, was observed in the total thickness distributions in two voyages. Comparison with Satellite images revealed that Such phenomena reflected the past breakup of the landfast ice. Within 20–30km from the Shore, total thickness as well as Snow depth decrease toward the Shore. This is due to the Snowdrift by the Strong northeasterly wind. Video observations of Sea-ice thickness and Snow depth were conducted on 11 voyages Since December 1987. Probability density functions derived from total thickness distributions in each year are categorized into three types: a thin-ice, thick-ice and intermediate type. Such interannual variability primarily depends on the extent and duration of the Successive break-up events.

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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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A sea-ice thickness retrieval model for 1.4 GHz radiometry and application to airborne measurements over low salinity sea-ice

The Cryosphere ◽

10.5194/tc-4-583-2010 ◽

2010 ◽

Vol 4 (4) ◽

pp. 583-592 ◽

Cited By ~ 59

Author(s):

L. Kaleschke ◽

N. Maaß ◽

C. Haas ◽

S. Hendricks ◽

G. Heygster ◽

...

Keyword(s):

Sea Ice ◽

Brightness Temperature ◽

Ice Thickness ◽

First Year ◽

Sea Ice Thickness ◽

Model Calculations ◽

Airborne Measurements ◽

Low Salinity ◽

Research Aircraft ◽

L Band

Abstract. In preparation for the European Space Agency's (ESA) Soil Moisture and Ocean Salinity (SMOS) mission, we investigated the potential of L-band (1.4 GHz) radiometry to measure sea-ice thickness. Sea-ice brightness temperature was measured at 1.4 GHz and ice thickness was measured along nearly coincident flight tracks during the SMOS Sea-Ice campaign in the Bay of Bothnia in March 2007. A research aircraft was equipped with the L-band Radiometer EMIRAD and coordinated with helicopter based electromagnetic induction (EM) ice thickness measurements. We developed a three layer (ocean-ice-atmosphere) dielectric slab model for the calculation of ice thickness from brightness temperature. The dielectric properties depend on the relative brine volume which is a function of the bulk ice salinity and temperature. The model calculations suggest a thickness sensitivity of up to 1.5 m for low-salinity (multi-year or brackish) sea-ice. For Arctic first year ice the modelled thickness sensitivity is less than half a meter. It reduces to a few centimeters for temperatures approaching the melting point. The campaign was conducted under unfavorable melting conditions and the spatial overlap between the L-band and EM-measurements was relatively small. Despite these disadvantageous conditions we demonstrate the possibility to measure the sea-ice thickness with the certain limitation up to 1.5 m. The ice thickness derived from SMOS measurements would be complementary to ESA's CryoSat-2 mission in terms of the error characteristics and the spatiotemporal coverage. The relative error for the SMOS ice thickness retrieval is expected to be not less than about 20%.

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Structural characteristics and development of sea ice in the western Ross Sea

Antarctic Science ◽

10.1017/s0954102093000094 ◽

1993 ◽

Vol 5 (1) ◽

pp. 63-75 ◽

Cited By ~ 31

Author(s):

M. O. Jeffries ◽

W. F. Weeks

Keyword(s):

Sea Ice ◽

Internal Structure ◽

Ross Sea ◽

Ice Cores ◽

Arctic Sea Ice ◽

Weddell Sea ◽

The Arctic ◽

Ice Thickness ◽

Pack Ice ◽

Western Ross Sea

The internal structure of ice cores from western Ross Sea pack ice floes showed considerable diversity. Snow-ice formation made a small, but significant contribution to ice growth. Frazil ice was common and its growth clearly occurred during both the pancake cycle and deformation events. Congelation ice was also common, in both its crystallographically aligned and non-aligned varieties. Platelet ice was found in only one core next to the Drygalski Ice Tongue, an observation adding to the increasing evidence that this unusual ice type occurs primarily in coastal pack ice near ice tongues and ice shelves. The diverse internal structure of the floes indicates that sea ice development in the Ross Sea is as complex as that in the Weddell Sea and more complex than in the Arctic. The mean ice thickness at the ice core sites varied between 0.71 m and 1.52 m. The thinnest ice generally occurred in the outer pack ice zone. Regardless of latitude, the ice thickness data are further evidence that Antarctic sea ice is thinner than Arctic sea ice.

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Early winter ice and snow thickness distribution, ice structure and development of the western Ross Sea pack ice between the ice edge and the Ross Ice Shelf

Antarctic Science ◽

10.1017/s0954102097000242 ◽

1997 ◽

Vol 9 (2) ◽

pp. 188-200 ◽

Cited By ~ 50

Author(s):

Martin O. Jeffries ◽

Ute Adolphs

Keyword(s):

Sea Ice ◽

Layer Thickness ◽

Ross Sea ◽

Ice Thickness ◽

First Year ◽

Ross Ice Shelf ◽

Antarctic Sea Ice ◽

Pack Ice ◽

Ice Edge ◽

Snow And Ice

A study of early winter first-year sea ice conditions and development in the western Ross Sea in May and June 1995 included measurements of snow and ice thickness, freeboard, ice core structure and stable isotopic composition. These variables showed strong spatial variability between the Ross Ice Shelf and the ice edge 1400 km to the north, and indicate that the development of the Ross Sea pack ice is quite different from that observed in other Antarctic sea ice zones. The thinnest snow and ice occurred in a 200 km wide coastal zone. The thickest snow and ice were observed in a continental shelf zone 200–600 km from the coast where the average ice thickness (0.8 m) determined by drilling is as thick as first-year sea ice later in winter elsewhere in Antarctica. A zone of moderate snow and ice thickness occurred on the deep ocean from 600 km to the ice edge at 1400 km. Thermodynamic thickening of the ice in the inner pack ice, <800 km from the coast, was dominated by congelation ice growth, which occurred in a greater amount (65%) and in thicker layers (mean: 20 cm) than was observed in the outer pack ice >800 km from the coast (amount: 22%; mean layer thickness: 12 cm) and elsewhere in the Antarctic pack ice. The preponderance of congelation ice in the inner pack ice might be due to a low oceanic heat flux on the Ross Sea continental shelf, and a colder, less stormy environment which favours the more frequent and prolonged calm conditions necessary for significant congelation ice growth. In the outer pack ice, thermodynamic thickening occurred mainly by snow ice formation (mean layer thickness: 20 cm) while dynamic processes, i.e., rafting and ridging, caused the thickening of frazil ice and columnar ice (mean layer thickness: 14 cm and 12 cm respectively). A greater amount of snow ice (37%) occurred in the outer pack ice than in the inner pack ice (15%), and both values indicate that in the Ross Sea, unlike other Antarctic sea ice zones, there can be significant seawater flooding of the snow/ice interface and snow ice formation before midwinter.

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Inferring first-year sea ice thickness using broadband echosounders

The Journal of the Acoustical Society of America ◽

10.1121/1.5068024 ◽

2018 ◽

Vol 144 (3) ◽

pp. 1819-1819

Author(s):

Christopher Bassett ◽

Andone C. Lavery ◽

Jeremy P. Wilkinson ◽

Ted Maksym ◽

Zoe R. Courville

Keyword(s):

Sea Ice ◽

Ice Thickness ◽

First Year ◽

Sea Ice Thickness

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Direct inference of first-year sea ice thickness using broadband acoustic backscattering

The Journal of the Acoustical Society of America ◽

10.1121/10.0000619 ◽

2020 ◽

Vol 147 (2) ◽

pp. 824-838

Author(s):

Christopher Bassett ◽

Andone C. Lavery ◽

Anthony P. Lyons ◽

Jeremy P. Wilkinson ◽

Ted Maksym

Keyword(s):

Sea Ice ◽

Ice Thickness ◽

First Year ◽

Direct Inference ◽

Sea Ice Thickness ◽

Acoustic Backscattering

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Sea ice representation in CMIP6 simulations with EC-Earth3-Veg

10.5194/egusphere-egu2020-20372 ◽

2020 ◽

Author(s):

Torben Koenigk ◽

Evelien Dekker

Keyword(s):

Sea Ice ◽

Emission Scenario ◽

Arctic Sea Ice ◽

The Arctic ◽

Ice Thickness ◽

First Year ◽

Data Sets ◽

Sea Ice Extent ◽

Sea Ice Thickness ◽

Arctic Sea

In this study, we compare the sea ice in ensembles of historical and future simulations with EC-Earth3-Veg to the sea ice of the NSIDC and OSA-SAF satellite data sets. The EC-Earth3-Veg Arctic sea ice extent generally matches well to the observational data sets, and the trend over 1980-2014 is captured correctly. Interestingly, the summer Arctic sea ice area minimum occurs already in August in the model. Mainly east of Greenland, sea ice area is overestimated. In summer, Arctic sea ice is too thick compared to PIOMAS. In March, sea ice thickness is slightly overestimated in the Central Arctic but in the Bering and Kara Seas, the ice thickness is lower than in PIOMAS.While the general picture of Arctic sea ice looks good, EC-Earth suffers from a warm bias in the Southern Ocean. This is also reflected by a substantial underestimation of sea ice area in the Antarctic.Different ensemble members of the future scenario projections of sea ice show a large range of the date of first year with a minimum ice area below 1 million square kilometers in the Arctic. The year varies between 2024 and 2056. Interestingly, this range does not differ very much with the emission scenario and even under the low emission scenario SSP1-1.9 summer Arctic sea ice almost totally disappears.

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