scholarly journals Evolution of the Amundsen Sea Polynya, Antarctica, 2016–2021

2021 ◽  
Author(s):  
Grant J. Macdonald ◽  
Stephen F. Ackley ◽  
Alberto M. Mestas-Nuñez
Keyword(s):  
Sea Ice ◽  
Reanalysis Data ◽  
Sea Ice Concentration ◽  
Amundsen Sea ◽  
Annual Variations ◽  
Ice Concentration ◽  
Ice Conditions ◽  
Sar Imagery ◽  
Key Sites ◽  
Ice Production

Abstract. Polynyas are key sites of ice production during the winter and are important sites of biological activity and carbon sequestration during the summer. The Amundsen Sea Polynya (ASP) is the fourth largest Antarctic polynya, has recorded the highest primary productivity and lies in an embayment of key oceanographic significance. However, knowledge of its dynamics, and of sub-annual variations in its area and ice production, is limited. In this study we primarily utilize Sentinel-1 SAR imagery, sea ice concentration products and climate reanalysis data, along with bathymetric data, to analyze the ASP over the period November 2016–March 2021. Specifically, we analyze (i) qualitative changes in the ASP's characteristics and dynamics, and quantitative changes in (ii) summer polynya area, (iii) winter polynya area and ice production. From our analysis of SAR imagery we find that ice produced by the ASP becomes stuck in the vicinity of the polynya and sometimes flows back into the polynya, contributing to its closure and limiting further ice production. The polynya forms westward off a persistent chain of grounded icebergs that are located at the site of a bathymetric high. Grounded icebergs also influence the outflow of ice and facilitate the formation of a 'secondary polynya' at times. Additionally, unlike some polynyas, ice produced by the polynya flows westward after formation, along the coast and into the neighboring sea sector. During the summer and early winter, broader regional sea ice conditions can play an important role in the polynya. The polynya opens in all summers, but record-low sea ice conditions in 2016/17 cause it to become part of the open ocean. During the winter, an average of 78 % of ice production occurs in April–May and September–October, but large polynya events often associated with high winds can cause ice production throughout the winter. While passive microwave data or daily sea ice concentration products remain key for analyzing variations in polynya area and ice production, we find that the ability to directly observe and qualitatively analyze the polynya at a high temporal and spatial resolution with Sentinel-1 imagery provides important insights about the behavior of the polynya that are not possible with those datasets.

Impact of the Mertz Glacier Tongue calving on the emergence of polynyas in the d'Urville Trough, East Antarctica

2020 ◽  
Author(s):  
Lucile Ricard ◽  
Marie-Noelle Houssais ◽  
Christophe Herbaut ◽  
Alexander Fraser ◽  
Rob Massom ◽  
...  
Keyword(s):  
Sea Ice ◽  
Microwave Remote Sensing ◽  
Sea Ice Concentration ◽  
Glacier Tongue ◽  
Pack Ice ◽  
Ice Concentration ◽  
Ice Conditions ◽  
Fast Ice ◽  
Ice Production ◽  
The Impact

<p> </p><p><br>Passive microwave remote sensing observations and atmospheric data are used to characterize the impact of the Mertz Glacier Tongue (MGT) calving in February 2010 on the sea ice conditions in the D’Urville Trough, East Antarctic shelf (139°E-141°E). The main objective is to determine if conditions for dense shelf water production in this area were possibly influenced by the calving. In particular, we look for the existence of winter polynyas capable of sustaining significant sea ice production, a prerequisite for the formation of dense, saline waters. We show that polynyas in the D'Urville area are part of a complex icescape made of fast ice and drifting pack ice. The seasonal evolution of this icescape has been profoundly modified with the calving of the MGT and opening of new polynyas. Pre-calving and post-calving sea ice concentrations are analyzed to identify major patterns of variability. Examination of the fast ice distribution and atmospheric forcing helps to develop a scenario for the formation of low sea ice concentration regions and their relation to the sea ice fluxes, supporting the conclusion that the role of the Adelie Bank as a barrier to the drift ice may have strengthened after the calving.</p>

scholarly journals Meteorological Drivers and Large-Scale Climate Forcing of West Antarctic Surface Melt

2019 ◽  
Vol 32 (3) ◽  
pp. 665-684 ◽  
Author(s):  
Ryan C. Scott ◽  
Julien P. Nicolas ◽  
David H. Bromwich ◽  
Joel R. Norris ◽  
Dan Lubin
Keyword(s):  
Sea Ice ◽  
Ice Sheet ◽  
Climate Forcing ◽  
West Antarctica ◽  
Sea Ice Concentration ◽  
Amundsen Sea ◽  
West Antarctic ◽  
Ice Concentration ◽  
Surface Melt ◽  
Marine Air

Understanding the drivers of surface melting in West Antarctica is crucial for understanding future ice loss and global sea level rise. This study identifies atmospheric drivers of surface melt on West Antarctic ice shelves and ice sheet margins and relationships with tropical Pacific and high-latitude climate forcing using multidecadal reanalysis and satellite datasets. Physical drivers of ice melt are diagnosed by comparing satellite-observed melt patterns to anomalies of reanalysis near-surface air temperature, winds, and satellite-derived cloud cover, radiative fluxes, and sea ice concentration based on an Antarctic summer synoptic climatology spanning 1979–2017. Summer warming in West Antarctica is favored by Amundsen Sea (AS) blocking activity and a negative phase of the southern annular mode (SAM), which both correlate with El Niño conditions in the tropical Pacific Ocean. Extensive melt events on the Ross–Amundsen sector of the West Antarctic Ice Sheet (WAIS) are linked to persistent, intense AS blocking anticyclones, which force intrusions of marine air over the ice sheet. Surface melting is primarily driven by enhanced downwelling longwave radiation from clouds and a warm, moist atmosphere and by turbulent mixing of sensible heat to the surface by föhn winds. Since the late 1990s, concurrent with ocean-driven WAIS mass loss, summer surface melt occurrence has increased from the Amundsen Sea Embayment to the eastern Ross Ice Shelf. We link this change to increasing anticyclonic advection of marine air into West Antarctica, amplified by increasing air–sea fluxes associated with declining sea ice concentration in the coastal Ross–Amundsen Seas.

Ocean Surface Connectivity in the Arctic: Capabilities and Caveats of Community Detection in Lagrangian Flow Networks

2021 ◽  
Author(s):  
Daan Reijnders ◽  
Erik Jan van Leeuwen ◽  
Erik van Sebille
Keyword(s):  
Sea Ice ◽  
Community Detection ◽  
The Arctic ◽  
Closed Domain ◽  
Sea Ice Concentration ◽  
Annual Variations ◽  
Detection Algorithms ◽  
Ice Concentration ◽  
Transport Barriers ◽  
Lagrangian Flow

<div><span>To identify barriers to transport in a fluid domain, community detection algorithms from network science have been used to divide the domain into clusters that are sparsely connected with each other. In a previous application to the closed domain of the Mediterranean Sea, communities detected by the <em>Infomap</em> algorithm have barriers that often coincide with well-known oceanographic features. We apply this clustering method to the surface of the Arctic and subarctic oceans and thereby show that it can also be applied to open domains. First, we construct a Lagrangian flow network by simulating the exchange of Lagrangian particles between different bins in an icosahedral-hexagonal grid. Then, <em>Infomap </em>is applied to identify groups of well-connected bins. The resolved transport barriers include naturally occurring structures, such as the major currents. As expected, clusters in the Arctic are affected by seasonal and annual variations in sea-ice concentration. An important caveat of community detection algorithms is that many different divisions into clusters may qualify as good solutions. Moreover, while certain cluster boundaries lie consistently at the same location between different good solutions, other boundary locations vary significantly, making it difficult to assess the physical meaning of a single solution. We therefore consider an ensemble of solutions to find persistent boundaries, trends and correlations with surface velocities and sea-ice cover.</span></div>

ALOS-2/PALSAR-2 dual-polarized L-band data for sea ice parameter estimation and sea ice classification 

2021 ◽  
Author(s):  
Juha Karvonen
Keyword(s):  
Parameter Estimation ◽  
Sea Ice ◽  
Sea Ice Concentration ◽  
Sea Ice Thickness ◽  
Ice Concentration ◽  
Sea Ice Drift ◽  
L Band ◽  
Sar Data ◽  
Dual Polarized ◽  
Sar Imagery

<p>This research is related to the JAXA 6th Research Announcement for the Advanced Land<br>Observing Satellite-2 (ALOS-2) project "Improved Sea Ice Parameter Estimation with L-Band SAR (ISIPELS)".<br>In the study ALOS-2/PALSAR-2 dual-polarized Horizontal-transmit-Horizontal-receive/<br>Horizontal-transmit-Vertical-receive (HH/HV) ScanSAR mode L-band  Synthetic Aperture Radar (SAR) imagery<br>over an Arctic study area were evaluated for their suitability for operational sea ice monitoring.<br>The SAR data consisting of about 140 HH/HV ScanSAR ALOS-2/PALSAR-2 images were acquired during the winter 2017.<br>These L-band SAR data were studied for estimation of different sea ice parameters:<br>sea ice concentration, sea ice thickness, sea ice type, sea ice drift. Also some comparisons with nearly<br>coincident C-band data over the same study area have been made. The results indicate that L-band<br>SAR data from ALOS-2/PALSAR-2 are very useful for estimating the studied sea ice parameters and equally good<br>or better than using the conventional operational dual-polarized C-band SAR satellite data.</p><p> </p>

Drivers of interannual sea ice variability on the Arctic continental margin north of Svalbard

2020 ◽  
Author(s):  
Øyvind Lundesgaard ◽  
Arild Sundfjord ◽  
Angelika H. H. Renner
Keyword(s):  
Sea Ice ◽  
Continental Margin ◽  
Barents Sea ◽  
Atlantic Water ◽  
Reanalysis Data ◽  
The Arctic ◽  
Upper Ocean ◽  
Ocean Temperature ◽  
Sea Ice Concentration ◽  
Ice Concentration

<p>Sea ice concentration along the Arctic continental margin north of Svalbard is in decline, but superimposed on this trend is considerable interannual variability. Many factors impact sea ice in this region, including atmospheric cooling and heating, winds, sea ice advection, and oceanic heat transport associated with the inflow of Atlantic Water, and regional sea ice cover remains difficult to predict. We present observations of upper ocean temperature between 2012 and 2017 from an ocean mooring located on the continental shelf break north of the Barents Sea, together with concurrent time series of atmospheric variables and sea ice concentration, drift, and thickness, derived from satellite and reanalysis data. While the inflow of Atlantic Water undoubtedly plays a key role in maintaining the area north of Svalbard ice-free through much of the year, variations in upper ocean temperature do not explain major interannual sea ice anomalies during the study period. Instead, we find that the magnitude of sea ice advection from the north and east was a major driver of interannual sea ice variability during our study.</p>

A System for Automated Vision-Based Sea-Ice Concentration Detection and Floe-Size Distribution Indication From an Icebreaker

2017 ◽  
Author(s):  
Hans-Martin Heyn ◽  
Martin Knoche ◽  
Qin Zhang ◽  
Roger Skjetne
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Size Distribution ◽  
Panoramic Image ◽  
Edge Detector ◽  
Image System ◽  
Camera System ◽  
Sea Ice Concentration ◽  
Ice Concentration ◽  
Ice Conditions

This paper presents a ship-mounted multi-lens camera system for sea-ice monitoring and algorithms to automatically evaluate the sea-ice concentration and to indicate the floe-sizes in a radius of 100 meter around the vessel. During the SWEDARCTIC Arctic Ocean 2016 expedition, 11 camera lenses recorded the sea-ice conditions around the Swedish icebreaker Oden. As an example of the possible use of this image system, the images of six lenses are combined into one 360° panoramic image. To distinguish between water and sea-ice in the images, and thus to evaluate the sea-ice concentration around the vessel, a direct thresholding, the k-means, and a novel adaptive thresholding method are applied. Moreover, an edge detector gives the number of pixels that either form the boundary between sea-ice and water or are part of a visible ice fracture. The ratio between these edge pixels and the total number of pixels containing sea-ice gives an indication of the floe size distribution (FSD) in the image.

scholarly journals Deep-sea benthic communities and oxygen fluxes in the Arctic Fram Strait controlled by sea-ice cover and water depth

2018 ◽  
Vol 15 (16) ◽  
pp. 4849-4869 ◽  
Author(s):  
Ralf Hoffmann ◽  
Ulrike Braeckman ◽  
Christiane Hasemann ◽  
Frank Wenzhöfer
Keyword(s):  
Sea Ice ◽  
Water Depth ◽  
Deep Sea ◽  
Abiotic Factors ◽  
Fram Strait ◽  
Sea Ice Concentration ◽  
Covered Area ◽  
Ice Concentration ◽  
Ice Conditions ◽  
Water Depths

Abstract. Arctic Ocean surface sea-ice conditions are linked with the deep sea benthic oxygen fluxes via a cascade of interdependencies across ecosystem components such as primary production, food supply, activity of the benthic community, and their functions. Additionally, each ecosystem component is influenced by abiotic factors such as light availability, temperature, water depth, and grain size structure. In this study, we investigated the coupling between surface sea-ice conditions and deep-sea benthic remineralization processes through a cascade of interdependencies in the Fram Strait. We measured sea-ice concentrations, a variety of different sediment characteristics, benthic community parameters, and oxygen fluxes at 12 stations of the LTER HAUSGARTEN observatory, Fram Strait, at water depths of 275–2500 m. Our investigations reveal that the Fram Strait is bisected into two long-lasting and stable regions: (i) a permanently and highly sea-ice-covered area and (ii) a seasonally and low sea-ice-covered area. Within the Fram Strait ecosystem, sea-ice concentration and water depth are two independent abiotic factors, controlling the deep-sea benthos. Sea-ice concentration correlated with the available food and water depth with the oxygen flux. In addition, both abiotic factors sea-ice concentration and water depth correlate with the macrofauna biomass. However, at water depths > 1500 m the influence of the surface sea-ice cover is minimal with water depth becoming more dominant. Benthic remineralization across the Fram Strait on average is  ∼ 1 mmol C m−2 d−1. Our data indicate that the portion of newly produced carbon that is remineralized by the benthos is 5 % in the seasonally low sea-ice-covered eastern part of Fram Strait but can be 14 % in the permanently high sea-ice-covered western part of Fram Strait. Here, by comparing a permanently sea-ice-covered area with a seasonally sea-ice-covered area, we discuss a potential scenario for the deep-sea benthic ecosystem in the future Arctic Ocean, in which an increased surface primary production may lead to increasing benthic remineralization at water depths < 1500 m.

scholarly journals Adélie penguins foraging consistency and site fidelity are conditioned by breeding status and environmental conditions

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0244298
Author(s):  
Candice Michelot ◽  
Akiko Kato ◽  
Thierry Raclot ◽  
Yan Ropert-Coudert
Keyword(s):  
Reproductive Success ◽  
Sea Ice ◽  
Site Fidelity ◽  
Environmental Changes ◽  
Foraging Activity ◽  
Sea Ice Concentration ◽  
Ice Concentration ◽  
Foraging Site ◽  
Ice Conditions ◽  
Adélie Penguins

There is a growing interest in studying consistency and site fidelity of individuals to assess, respectively, how individual behaviour shapes the population response to environmental changes, and to highlight the critical habitats needed by species. In Antarctica, the foraging activity of central place foragers like Adélie penguins (Pygoscelis adeliae) is constrained by the sea-ice cover during the breeding season. We estimated the population-level repeatability in foraging trip parameters and sea-ice conditions encountered by birds across successive trips over several years, and we examined their foraging site fidelity linked to sea-ice concentrations throughout the chick-rearing season. Penguins’ foraging activity was repeatable despite varying annual sea-ice conditions. Birds’ site fidelity is constrained by both sea-ice conditions around the colony that limit movements and resources availability, and also behavioural repeatability of individuals driven by phenological constraints. Adélie penguins favoured sea-ice concentrations between 20–30%, as these facilitate access to open water while opening multiple patches for exploration in restricted areas in case of prey depletion. When the sea-ice concentration became greater than 30%, foraging site fidelity decreased and showed higher variability, while it increased again after 60%. Between two trips, the foraging site fidelity remained high when sea-ice concentration changed by ± 10% but showed greater variability when sea-ice concentrations differed on a larger range. In summary, Adélie penguins specialize their foraging behaviour during chick-rearing according to sea-ice conditions to enhance their reproductive success. The balance between being consistent under favourable environmental conditions vs. being flexible under more challenging conditions may be key to improving foraging efficiency and reproductive success to face fast environmental changes.

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