scholarly journals Iceberg signatures and detection in SAR images in two test regions of the Weddell Sea, Antarctica

2012 ◽  
Vol 58 (208) ◽  
pp. 325-339 ◽  
Author(s):  
Christine Wesche ◽  
Wolfgang Dierking
Keyword(s):  
Sea Ice ◽  
Open Water ◽  
Longitudinal Axis ◽  
Weddell Sea ◽  
Minimum Size ◽  
Speckle Reduction ◽  
Automatic Identification ◽  
Detection Accuracy ◽  
Sar Images ◽  
Ice Conditions

AbstractA pixel-based methodology has been established for automatic identification of icebergs in satellite synthetic aperture radar (SAR) images acquired during different seasons and for different sea- ice conditions. This includes, in particular, smaller icebergs (longitudinal axis 100 m to 18.5 km). Investigations were carried out for two test regions located in the Weddell Sea, Antarctica, using images of the Envisat Advanced SAR (ASAR) at HH polarization and of the European Remote-sensing Satellite-2 (ERS-2) SAR (VV-polarized). From the former, a sequence of Image Mode and Wide Swath Mode data are available for the whole of 2006. The ERS data were acquired around the tip of the Antarctic Peninsula in spring and summer months of the years 2000-03. The minimum size of icebergs that could be identified in the IM images was <0.02 km2. Radar backscattering coefficients of icebergs, sea ice and open water were determined separately. We demonstrate that the error in separating icebergs from their surroundings (sea ice or open water) depends on meteorological, oceanographic and sea-ice conditions. Also the pre-processing of the SAR images (e.g. speckle reduction) influences iceberg recognition. Differences in detection accuracy as a function of season could not be substantiated for our test sites, but have in general to be taken into account, as results of other investigations indicate.

Early detection of the Weddell polynya re-opening using SAR imagery

2020 ◽  
Author(s):  
Adriano Lemos ◽  
Céline Heuzé
Keyword(s):  
Early Detection ◽  
Sea Ice ◽  
Open Water ◽  
Weddell Sea ◽  
Small Scale ◽  
Ice Thickness ◽  
Sar Images ◽  
Sea Ice Thickness ◽  
Sar Imagery ◽  
Microwave Sensors

&lt;p&gt;The sea ice thickness in the Weddell Sea during the austral winter normally exceeds 1 m, but in the case of a polynya, this thickness decreases to 10 cm or less. There are two theories as to why the Weddell Polynya opens: 1) comparatively warm oceanic water upwelling from its nominal depth of several hundred metres to the surface where it melts the sea ice from underneath; or 2) opening of a lead by a passing storm, lead which will then be maintained open either by the atmosphere or ocean and grow. The objective of this study is to estimate how long in advance the recent Weddell Polynya opening could have been detected by synthetic aperture radar (SAR) images due to the decrease of the sea ice thickness and/or early appearance of leads. We use high temporal and spatial resolution SAR images from the Sentinel-1 constellation (C-band) and ALOS2 (L-band) during the austral winters 2014-2018. We use an adapted version of the algorithm developed by Aldenhoff et al. (2018) to monitor changes in sea ice thickness over the polynya region. The algorithm detects the transition of the sea ice thickness through changes in small scale surface roughness and thus reduced backscatter, and allowing us to distinguish three different categories: ice, thin ice, and open water. The transition from ice to thin ice and then to open water indicates that the polynya is melted from under, whereas a direct transition from ice to open water will reveal leads. The high resolution and good coverage of the SAR imagery, and a combined effort of different satellites sensors (e.g. infrared and microwave sensors), opens the possibility of an early detection of Weddell Polynya opening.&lt;/p&gt;

The Weddell Sea Expedition 2019

2020 ◽  
Author(s):  
John Shears ◽  
Julian Dowdeswell ◽  
Freddie Ligthelm ◽  
Paul Wachter
Keyword(s):  
Sea Ice ◽  
Autonomous Underwater Vehicles ◽  
Remote Sensing Data ◽  
Open Water ◽  
Weddell Sea ◽  
Scientific Programme ◽  
Ice Shelf ◽  
Remotely Operated Vehicle ◽  
Radar Images ◽  
Ice Conditions

&lt;p&gt;The Weddell Sea Expedition 2019 (WSE) was conceived with dual aims: (i) to undertake a comprehensive international inter-disciplinary programme of science centred in the waters around Larsen C Ice Shelf, western Weddell Sea; and (ii) to search for, survey and image the wreck of Sir Ernest Shackleton&amp;#8217;s Endurance, which sank in the Weddell Sea in 1915.&amp;#160;&lt;/p&gt;&lt;p&gt;The 6-week long expedition, funded by the Flotilla Foundation, required the use of a substantial ice-strengthened vessel given the very difficult sea-ice conditions encountered in the Weddell Sea, and especially in its central and western parts. The South African ship SA Agulhas II was chartered for its Polar Class 5 icebreaking capability and design as a scientific research vessel. The expedition was equipped with state-of-the-art Autonomous Underwater Vehicles (AUVs) and a Remotely Operated Vehicle (ROV) which were capable of deployment to waters more than 3,000 m deep, thus making the Larsen C continental shelf and slope, and the Endurance wreck site, accessible. During the expedition, a suite of passive and active remote-sensing data, including TerraSAR-X radar images delivered in near real-time, was provided to the ice-pilot onboard the SA Agulhas II. These data were instrumental for safe vessel navigation in sea ice and the detection and tracking of icebergs and ice floes of scientific interest.&lt;/p&gt;&lt;p&gt;The scientific programme undertaken by the WSE was very successful and produced many new geological, geophysical, marine biological and oceanographic observations from a part of the Weddell Sea that has been little studied previously, particularly the area east of Larsen C Ice Shelf. The expedition also reached the sinking location of Shackleton&amp;#8217;s Endurance, where the presence of open-water sea ice leads allowed the deployment of an AUV to the ocean floor to try and locate and survey the wreck. Unfortunately, SA Agulhas II later lost communication with the AUV, and deteriorating weather and sea ice conditions meant that the search had to be called off.&lt;/p&gt;

scholarly journals Sea ice draft in the Weddell Sea, measured by upward looking sonars

2013 ◽  
Vol 5 (1) ◽  
pp. 209-226 ◽  
Author(s):  
A. Behrendt ◽  
W. Dierking ◽  
E. Fahrbach ◽  
H. Witte
Keyword(s):  
Sea Ice ◽  
Sound Speed ◽  
Open Water ◽  
Weddell Sea ◽  
Reference Level ◽  
Austral Winter ◽  
Processing Procedure ◽  
Basic Parameters ◽  
Measurement Principle ◽  
Data Processing Procedure

Abstract. The presented database contains time-referenced sea ice draft values from upward looking sonar (ULS) measurements in the Weddell Sea, Antarctica. The sea ice draft data can be used to infer the thickness of the ice. They were collected during the period 1990–2008. In total, the database includes measurements from 13 locations in the Weddell Sea and was generated from more than 3.7 million measurements of sea ice draft. The files contain uncorrected raw drafts, corrected drafts and the basic parameters measured by the ULS. The measurement principle, the data processing procedure and the quality control are described in detail. To account for the unknown speed of sound in the water column above the ULS, two correction methods were applied to the draft data. The first method is based on defining a reference level from the identification of open water leads. The second method uses a model of sound speed in the oceanic mixed layer and is applied to ice draft in austral winter. Both methods are discussed and their accuracy is estimated. Finally, selected results of the processing are presented. The data can be downloaded from doi:10.1594/PANGAEA.785565.

scholarly journals Albedo of the ice covered Weddell and Bellingshausen Seas

2012 ◽  
Vol 6 (2) ◽  
pp. 479-491 ◽  
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.

scholarly journals A reinterpretation of sea-salt records in Greenland and Antarctic ice cores?

2004 ◽  
Vol 39 ◽  
pp. 276-282 ◽  
Author(s):  
Andrew M. Rankin ◽  
Eric W. Wolff ◽  
Robert Mulvaney
Keyword(s):  
Sea Ice ◽  
Ice Core ◽  
Open Water ◽  
Weddell Sea ◽  
Sea Salt ◽  
Sea Salt Aerosol ◽  
Ice Surface ◽  
Frost Flowers ◽  
Ice Production ◽  
Ice Core Records

AbstractIt has recently been shown that much sea-salt aerosol around the coast of Antarctica is generated not from open water, but from the surface of newly formed sea ice. Previous interpretations of ice-core records have disregarded the sea-ice surface as a source of sea salt. The majority of sea-salt aerosol at Halley research station originates from frost flowers rather than open water, and the seasonal cycle of sea salt in aerosol at Halley appears to be controlled by ice production in the Weddell Sea, as well as variations in wind speed. Frost flowers are also an important source of aerosol at Siple Dome, suggesting that variations in sea-salt concentrations in the core, and other cores drilled in similar locations, may be reflecting changes in sea-ice production rather than changes in transportation patterns. For Greenland cores, and those from low-accumulation inland sites in Antarctica, it is not simple to calculate the proportion of sea salt originating from frost flowers rather than open water. However, modelling studies suggest that a sea-ice surface source contributed much of the flux of sea salt to these sites in glacial periods, suggesting that interpretations of ice-core records from these locations should also be revisited.

scholarly journals Sea-floor and sea-ice conditions in the western Weddell Sea, Antarctica, around the wreck of Sir Ernest Shackleton's Endurance

2020 ◽  
Vol 32 (4) ◽  
pp. 301-313 ◽  
Author(s):  
Julian A. Dowdeswell ◽  
Christine L. Batchelor ◽  
Boris Dorschel ◽  
Toby J. Benham ◽  
Frazer D.W. Christie ◽  
...  
Keyword(s):  
Sea Ice ◽  
Autonomous Underwater Vehicles ◽  
Underwater Vehicles ◽  
Weddell Sea ◽  
Energy Conditions ◽  
Mass Wasting ◽  
Sea Floor ◽  
Fine Grained ◽  
Ice Conditions ◽  
Sedimentary System

AbstractMarine-geophysical evidence on sea-floor morphology and shallow acoustic stratigraphy are used to examine the substrate around the location at which Sir Ernest Shackleton's ship Endurance sank in 1915 and on the continental slope-shelf sedimentary system above this site in the western Weddell Sea. Few signs of turbidity-current and mass-wasting activity are found near or upslope of the wreck site, and any such activity was probably linked to full-glacial higher-energy conditions when ice last advanced across the continental shelf. The wreck is well below the maximum depth of iceberg keels and will not have been damaged by ice-keel ploughing. The wreck has probably been draped by only a few centimetres of fine-grained sediment since it sank in 1915. Severe modern sea-ice conditions hamper access to the wreck site. Accessing and investigating the wreck of Endurance in the Weddell Sea therefore represents a significant challenge. An ice-breaking research vessel is required, and even this would not guarantee that the site could be reached. Heavy sea-ice cover at the wreck site, similar to that encountered by Agulhus II during the Weddell Sea Expedition 2019, would also make the launch and recovery of autonomous underwater vehicles and remotely operated vehicles deployed to investigate the Endurance wreck problematic.

scholarly journals Sea-Ice Investigations In The Weddell Sea During The German Antarctic Expedition 1979-80

1983 ◽  
Vol 4 ◽  
pp. 246-252 ◽  
Author(s):  
Joachim Schwarz
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Sea Ice ◽  
Young’S Modulus ◽  
Uniaxial Compressive Strength ◽  
Young's Modulus ◽  
Weddell Sea ◽  
Ice Shelves ◽  
Antarctic Expedition ◽  
Ice Conditions

In the austral winter of 1979-80, a German Antarctic expedition was sent by ship to the Filchner and Ronne ice shelves in order to find a suitable site for the establishment of a permanent Antarctic station. During this expedition, investigations were carried out on sea ice in the Weddell Sea in order to evaluate the accessibility of the site for icebreaking ships which are intended to convey construction materials to the site and, later on, to supply the station annually.This paper covers the results of investigations on sea-ice conditions during the voyage along the ice shelves from Cape Fiske (at the base of the Antarctic Peninsula) to Atka Bay with emphasis on sea-ice conditions in the area about 100 km north-west of Berkner Island (Fig.1.). In addition to the drift conditions (speed, direction), a special feature of multi-year sea ice is described. The main part of the paper deals with mechanical properties such as flexural strength, uniaxial compressive strength and Young’s modulus of columnar-grained sea ice from the southern border of the Weddell Sea. Salinities and temperatures were measured over the depth of the ice and used for calculating the flexural strength and the Young’s modulus of the ice. The uniaxial compressive strength was investigated as a function of strain-rate, brine volume and temperature on a closed-loop testing machine on samples which were carried back from Antarctica to Hamburg.

New records of mummified crabeater seals on islands bordering Admiralty Sound, Weddell Sea

2019 ◽  
Vol 31 (3) ◽  
pp. 109-115
Author(s):  
Javier Negrete ◽  
Leopoldo H. Soibelzon ◽  
Esteban Soibelzon ◽  
Jorge Lusky
Keyword(s):  
Open Water ◽  
Weddell Sea ◽  
Pack Ice ◽  
Breeding Grounds ◽  
Ice Conditions ◽  
Crabeater Seals ◽  
Ice Floes ◽  
Early Breakup ◽  
Natural Trap ◽  
Seymour Island

AbstractNinety-six mummified crabeater seals discovered at Seymour Island (Isla Marambio) are reported. Each specimen was georeferenced, photographed and assigned to five different taphonomic states. Previous work stated that seals at Seymour Island get stranded inland around the breeding season. However, it is not clear if the species breeds in this area. The abundance of crabeater seals and the ice condition along Admiralty Sound (Estrecho Bouchard) were obtained by aerial surveys during spring (2015–17). It appears that the species uses the strait as a passage to breeding grounds. Under heavy ice conditions, the seals become stranded in the middle section of this strait and wander inland through a valley that represents the mouth of an ephemeral stream that ends at the pack ice level. This situation was observed in 2014 and 2015 when recently dead seals were found, evidencing that this natural trap is still active. Nonetheless, in 2016 and 2017, during an early breakup of Admiralty Sound, the seals that remained in the area were more numerous than in 2015 but they did not get stranded inland. This early breakup may encourage the seals to breed there in the presence of open water areas with ice floes.

scholarly journals Long-distance swimming by polar bears (Ursus maritimus) of the southern Beaufort Sea during years of extensive open water

2012 ◽  
Vol 90 (5) ◽  
pp. 663-676 ◽  
Author(s):  
A.M. Pagano ◽  
G.M. Durner ◽  
S.C. Amstrup ◽  
K.S. Simac ◽  
G.S. York
Keyword(s):  
Sea Ice ◽  
Adult Female ◽  
Open Water ◽  
Ursus Maritimus ◽  
Polar Bears ◽  
Long Distance ◽  
Gps Collars ◽  
Movement Data ◽  
Global Positioning ◽  
Ice Conditions

Polar bears ( Ursus maritimus Phipps, 1774) depend on sea ice for catching marine mammal prey. Recent sea-ice declines have been linked to reductions in body condition, survival, and population size. Reduced foraging opportunity is hypothesized to be the primary cause of sea-ice-linked declines, but the costs of travel through a deteriorated sea-ice environment also may be a factor. We used movement data from 52 adult female polar bears wearing Global Positioning System (GPS) collars, including some with dependent young, to document long-distance swimming (>50 km) by polar bears in the southern Beaufort and Chukchi seas. During 6 years (2004–2009), we identified 50 long-distance swims by 20 bears. Swim duration and distance ranged from 0.7 to 9.7 days (mean = 3.4 days) and 53.7 to 687.1 km (mean = 154.2 km), respectively. Frequency of swimming appeared to increase over the course of the study. We show that adult female polar bears and their cubs are capable of swimming long distances during periods when extensive areas of open water are present. However, long-distance swimming appears to have higher energetic demands than moving over sea ice. Our observations suggest long-distance swimming is a behavioral response to declining summer sea-ice conditions.

Sign in / Sign up

Export Citation Format

Share Document