scholarly journals Sea-ice freeboard and thickness in the Ross Sea from airborne (IceBridge 2013) and satellite (ICESat 2003–2008) observations

2020 ◽  
Vol 61 (82) ◽  
pp. 24-39 ◽  
Author(s):  
Liuxi Tian ◽  
Hongjie Xie ◽  
Stephen F. Ackley ◽  
Jiakui Tang ◽  
Alberto M. Mestas-Nuñez ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ross Sea ◽  
Deep Ocean ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Sea Ice Thickness ◽  
Mean Values ◽  
Digital Mapping ◽  
Mapping System ◽  
Two Peaks

AbstractNASA's Operation IceBridge mission flew over the Ross Sea, Antarctica (20 and 27 November 2013) and collected data with Airborne Topographic Mapper (ATM) and Digital Mapping System (DMS). Using the DMS and reflectivity of ATM L1B, leads are detected to define local sea level height. The total freeboard is then obtained and converted to ice thickness. The estimated mean sea-ice thickness values are found to be in the 0.48–0.99 m range. Along the N-S track, sea ice was thinner southward rather than northward of the fluxgate, resulting in two peaks of modal thickness: 0.35 m (south) and 0.7 m (north). This supports that new ice produced in coastal polynyas is transported northward by katabatic winds off the ice-shelf. The lowest (2%) elevation method used for freeboard retrieval for ICESat is also tested for ATM data. It is found that the lowest elevation method tends to overestimate freeboard, but mean values are less affected than mode values. Using mean thickness values of ICESat and ATM along the ‘fluxgate’, separating the shelf from the deep ocean, the exported ice volume at this ‘fluxgate’ is found to be higher during the ICESat years (2003–2008) than during the IceBridge year (2013).

Sea ice deformation and thickness in the Western Ross Sea

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

<p>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.</p><p>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<sup>-1</sup> in early October deformed the pack ice, which was surveyed more than a month later.</p><p>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.</p><p>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.</p>

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

2003 ◽  
Vol 15 (1) ◽  
pp. 47-54 ◽  
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.

Salinity evolution and mechanical properties of snow-loaded multiyear sea ice near an ice shelf

2013 ◽  
Vol 25 (6) ◽  
pp. 821-831 ◽  
Author(s):  
A.J. Gough ◽  
A.R. Mahoney ◽  
P.J. Langhorne ◽  
T.G. Haskell
Keyword(s):  
Mechanical Properties ◽  
Sea Ice ◽  
Strain Rate ◽  
Ice Thickness ◽  
First Year ◽  
Ice Shelf ◽  
Sea Ice Thickness ◽  
Ice Shelves ◽  
Complex Region ◽  
Salinity Profile

AbstractSea ice often forms attached to floating ice shelves. Accumulating snow can depress its freeboard, creating a flooded slush layer that may subsequently freeze to form snow ice, rejecting brine as it freezes. The resulting salinity profile determines the mechanical properties of the sea ice. We provide measurements of snow-loaded, multiyear sea ice from summer to winter. Brine from a slush layer is not completely expelled from the sea ice when the slush refreezes to form snow ice. Measurements of sea ice salinity and temperature indicate that the fate of this brine depends on the permeability of the sea ice below it. The sea ice in this study was also deformed by a nearby ice shelf over eleven years at a strain rate $$--&#x003E;&#x003C;$&#x003E; \dot{{\epsilon}} $$$ = (-8 ± 3) × 10-4 yr-1 (or 3 × 10-11 s-1). From transects of sea ice thickness and structure we estimate an effective Young's modulus at medium scales for sea ice mostly composed of snow ice of 0.1 GPa < E < 0.4 GPa, suggesting that this eleven year old sea ice cover has similar mechanical properties to warm first year sea ice. This is important for the parameterisations needed to simulate multiyear sea ice in the complex region near an ice shelf.

scholarly journals Sea-ice thickness and roughness in the Ross Sea, Antarctica

2001 ◽  
Vol 33 ◽  
pp. 187-193 ◽  
Author(s):  
Tina Tin ◽  
Martin O. Jeffries
Keyword(s):  
Surface Roughness ◽  
Sea Ice ◽  
Ross Sea ◽  
Geographical Location ◽  
Ice Thickness ◽  
Snow Surface ◽  
Sea Ice Thickness ◽  
Antarctic Sea Ice ◽  
Ice Roughness ◽  
Ice Floes

AbstractSea-ice thickness and roughness data collected on three cruises in the Ross Sea, Antarctica, showed interseasonal, regional and interannual variability. Variability was reduced to season, or age of ice floe, when sea-ice roughness values from around Antarctica were compared. There were statistically significant correlations between mean snow elevation and mean ice thickness; snow surface roughness and mean ice thickness; and snow surface roughness and ice bottom roughness, which appeared to be independent of season, geographical location and deformation history of ice floes. Our field data indicate that ice thickness can be predicted from snow elevation measurements with higher accuracy in summer. The feasibility of using snow surface roughness to infer ice thickness and ice bottom roughness is promising, and can provide us with a means to study the thickness and underside of Antarctic sea ice at good spatial and temporal resolution.

Estimating the annual cycle of sea-ice thickness and volume in the Ross Sea

2011 ◽  
Vol 58 (9-10) ◽  
pp. 1250-1260 ◽  
Author(s):  
Tracy L. DeLiberty ◽  
Cathleen A. Geiger ◽  
Stephen F. Ackley ◽  
Anthony P. Worby ◽  
Michael L. Van Woert
Keyword(s):  
Sea Ice ◽  
Annual Cycle ◽  
Ross Sea ◽  
Ice Thickness ◽  
Sea Ice Thickness

scholarly journals Sea Ice Thickness in the Western Ross Sea

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

scholarly journals Sea-ice production and air/ice/ocean/biogeochemistry interactions in the Ross Sea during the PIPERS 2017 autumn field campaign

2020 ◽  
Vol 61 (82) ◽  
pp. 181-195 ◽  
Author(s):  
S. F. Ackley ◽  
S. Stammerjohn ◽  
T. Maksym ◽  
M. Smith ◽  
J. Cassano ◽  
...  
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Multidisciplinary Approach ◽  
Ross Sea ◽  
Ice Thickness ◽  
Biogeochemical Processes ◽  
Sea Ice Thickness ◽  
Ocean Biogeochemistry ◽  
Ice Edge ◽  
Ice Production

AbstractThe Ross Sea is known for showing the greatest sea-ice increase, as observed globally, particularly from 1979 to 2015. However, corresponding changes in sea-ice thickness and production in the Ross Sea are not known, nor how these changes have impacted water masses, carbon fluxes, biogeochemical processes and availability of micronutrients. The PIPERS project sought to address these questions during an autumn ship campaign in 2017 and two spring airborne campaigns in 2016 and 2017. PIPERS used a multidisciplinary approach of manned and autonomous platforms to study the coupled air/ice/ocean/biogeochemical interactions during autumn and related those to spring conditions. Unexpectedly, the Ross Sea experienced record low sea ice in spring 2016 and autumn 2017. The delayed ice advance in 2017 contributed to (1) increased ice production and export in coastal polynyas, (2) thinner snow and ice cover in the central pack, (3) lower sea-ice Chl-a burdens and differences in sympagic communities, (4) sustained ocean heat flux delaying ice thickening and (5) a melting, anomalously southward ice edge persisting into winter. Despite these impacts, airborne observations in spring 2017 suggest that winter ice production over the continental shelf was likely not anomalous.

scholarly journals The sub-ice platelet layer and its influence on freeboard to thickness conversion of Antarctic sea ice

2014 ◽  
Vol 8 (1) ◽  
pp. 999-1022 ◽  
Author(s):  
D. Price ◽  
W. Rack ◽  
P. J. Langhorne ◽  
C. Haas ◽  
G. Leonard ◽  
...  
Keyword(s):  
Sea Ice ◽  
Solid Fraction ◽  
Surface Elevation ◽  
Ice Thickness ◽  
Shelf Water ◽  
Ice Shelf ◽  
Sea Ice Thickness ◽  
Ice Shelves ◽  
Antarctic Sea Ice ◽  
Ice Shelf Water

Abstract. This is an investigation to quantify the influence of the sub-ice platelet layer on satellite measurements of total freeboard and their conversion to thickness of Antarctic sea ice. The sub-ice platelet layer forms as a result of the seaward advection of supercooled ice shelf water from beneath ice shelves. This ice shelf water provides an oceanic heat sink promoting the formation of platelet crystals which accumulate at the sea ice–ocean interface. The build-up of this porous layer increases sea ice freeboard, and if not accounted for, leads to overestimates of sea ice thickness from surface elevation measurements. In order to quantify this buoyant effect, the solid fraction of the sub-ice platelet layer must be estimated. An extensive in situ data set measured in 2011 in McMurdo Sound in the south-western Ross Sea is used to achieve this. We use drill-hole measurements and the hydrostatic equilibrium assumption to estimate a mean value for the solid fraction of this sub-ice platelet layer of 0.16. This is highly dependent upon the uncertainty in sea ice density. We test this value with independent Global Navigation Satellite System (GNSS) surface elevation data to estimate sea ice thickness. We find that sea ice thickness can be overestimated by up to 19%, with a mean deviation of 12% as a result of the influence of the sub-ice platelet layer. It is concluded that in close proximity to ice shelves this influence should be considered universally when undertaking sea ice thickness investigations using remote sensing surface elevation measurements.

scholarly journals Autumn sea ice thickness, ridging and heat flux variability in and adjacent to Terra Nova Bay, Ross Sea, Antarctica

2001 ◽  
Vol 106 (C3) ◽  
pp. 4437-4448 ◽  
Author(s):  
Martin O. Jeffries ◽  
Kim Morris ◽  
Ted Maksym ◽  
Nickolai Kozlenko ◽  
Tina Tin
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Ross Sea ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
Terra Nova Bay ◽  
Flux Variability ◽  
Terra Nova

scholarly journals The sub-ice platelet layer and its influence on freeboard to thickness conversion of Antarctic sea ice

2014 ◽  
Vol 8 (3) ◽  
pp. 1031-1039 ◽  
Author(s):  
D. Price ◽  
W. Rack ◽  
P. J. Langhorne ◽  
C. Haas ◽  
G. Leonard ◽  
...  
Keyword(s):  
Sea Ice ◽  
Solid Fraction ◽  
Surface Elevation ◽  
Ice Thickness ◽  
Shelf Water ◽  
Ice Shelf ◽  
Data Set ◽  
Sea Ice Thickness ◽  
Antarctic Sea Ice ◽  
Ice Shelf Water

Abstract. This is an investigation to quantify the influence of the sub-ice platelet layer on satellite measurements of total freeboard and their conversion to thickness of Antarctic sea ice. The sub-ice platelet layer forms as a result of the seaward advection of supercooled ice shelf water from beneath ice shelves. This ice shelf water provides an oceanic heat sink promoting the formation of platelet crystals which accumulate at the sea ice–ocean interface. The build-up of this porous layer increases sea ice freeboard, and if not accounted for, leads to overestimates of sea ice thickness from surface elevation measurements. In order to quantify this buoyant effect, the solid fraction of the sub-ice platelet layer must be estimated. An extensive in situ data set measured in 2011 in McMurdo Sound in the southwestern Ross Sea is used to achieve this. We use drill-hole measurements and the hydrostatic equilibrium assumption to estimate a mean value for the solid fraction of this sub-ice platelet layer of 0.16. This is highly dependent upon the uncertainty in sea ice density. We test this value with independent Global Navigation Satellite System (GNSS) surface elevation data to estimate sea ice thickness. We find that sea ice thickness can be overestimated by up to 19%, with a mean deviation of 12% as a result of the influence of the sub-ice platelet layer. It is concluded that within 100 km of an ice shelf this influence might need to be considered when undertaking sea ice thickness investigations using remote sensing surface elevation measurements.

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