Multidecadal #observations of the #Antarctic #icesheet from restored analog #radar #records (Proc Natl Acad Sci USA, abstract)

[Source: Proceedings of the National Academy of Sciences of the United States of America, full page: (LINK). Abstract, edited.]

Multidecadal observations of the Antarctic ice sheet from restored analog radar records

Dustin M. Schroeder, Julian A. Dowdeswell, Martin J. Siegert, Robert G. Bingham, Winnie Chu, Emma J. MacKie, Matthew R. Siegfried, Katherine I. Vega, John R. Emmons, and Keith Winstein

PNAS first published September 3, 2019 / DOI: https://doi.org/10.1073/pnas.1821646116

Edited by Eric Rignot, University of California, Irvine, CA, and approved August 8, 2019 (received for review December 19, 2018)

 

Significance

One of the greatest challenges in projecting the sea-level contributions of ice sheets over the next century is the lack of observations of conditions within and underneath the ice sheet that span more than a decade or two. By digitizing archival ice-penetrating radar data recorded in the 1970s on 35-mm optical film, we can compare modern and archival radar-sounding data at their full resolution in order to observe changes in the Antarctic ice sheet over more than 40 y. This makes it possible to investigate and model subsurface processes over both large scales and several decades for the first time.

 

Abstract

Airborne radar sounding can measure conditions within and beneath polar ice sheets. In Antarctica, most digital radar-sounding data have been collected in the last 2 decades, limiting our ability to understand processes that govern longer-term ice-sheet behavior. Here, we demonstrate how analog radar data collected over 40 y ago in Antarctica can be combined with modern records to quantify multidecadal changes. Specifically, we digitize over 400,000 line kilometers of exploratory Antarctic radar data originally recorded on 35-mm optical film between 1971 and 1979. We leverage the increased geometric and radiometric resolution of our digitization process to show how these data can be used to identify and investigate hydrologic, geologic, and topographic features beneath and within the ice sheet. To highlight their scientific potential, we compare the digitized data with contemporary radar measurements to reveal that the remnant eastern ice shelf of Thwaites Glacier in West Antarctica had thinned between 10 and 33% between 1978 and 2009. We also release the collection of scanned radargrams in their entirety in a persistent public archive along with updated geolocation data for a subset of the data that reduces the mean positioning error from 5 to 2.5 km. Together, these data represent a unique and renewed extensive, multidecadal historical baseline, critical for observing and modeling ice-sheet change on societally relevant timescales.

Antarctica – radio echo sounding – glaciology – remote sensing – archival data

Keywords: Antarctica; Climate change; Global warming.

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A 40-y record reveals gradual #Antarctic #sea #ice increases followed by decreases at rates far exceeding the rates seen in the #Arctic (Proc Natl Acad Sci USA, abstract)

[Source: Proceedings of the National Academy of Sciences of the United States of America, full page: (LINK). Abstract, edited.]

A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic

Claire L. Parkinson

PNAS first published July 1, 2019 / DOI: https://doi.org/10.1073/pnas.1906556116

Contributed by Claire L. Parkinson, May 24, 2019 (sent for review April 16, 2019; reviewed by Will Hobbs and Douglas G. Martinson)

 

Significance

A newly completed 40-y record of satellite observations is used to quantify changes in Antarctic sea ice coverage since the late 1970s. Sea ice spreads over vast areas and has major impacts on the rest of the climate system, reflecting solar radiation and restricting ocean/atmosphere exchanges. The satellite record reveals that a gradual, decades-long overall increase in Antarctic sea ice extents reversed in 2014, with subsequent rates of decrease in 2014–2017 far exceeding the more widely publicized decay rates experienced in the Arctic. The rapid decreases reduced the Antarctic sea ice extents to their lowest values in the 40-y record, both on a yearly average basis (record low in 2017) and on a monthly basis (record low in February 2017).

 

Abstract

Following over 3 decades of gradual but uneven increases in sea ice coverage, the yearly average Antarctic sea ice extents reached a record high of 12.8 × 106 km2 in 2014, followed by a decline so precipitous that they reached their lowest value in the 40-y 1979–2018 satellite multichannel passive-microwave record, 10.7 × 106 km2, in 2017. In contrast, it took the Arctic sea ice cover a full 3 decades to register a loss that great in yearly average ice extents. Still, when considering the 40-y record as a whole, the Antarctic sea ice continues to have a positive overall trend in yearly average ice extents, although at 11,300 ± 5,300 km2⋅y−1, this trend is only 50% of the trend for 1979–2014, before the precipitous decline. Four of the 5 sectors into which the Antarctic sea ice cover is divided all also have 40-y positive trends that are well reduced from their 2014–2017 values. The one anomalous sector in this regard, the Bellingshausen/Amundsen Seas, has a 40-y negative trend, with the yearly average ice extents decreasing overall in the first 3 decades, reaching a minimum in 2007, and exhibiting an overall upward trend since 2007 (i.e., reflecting a reversal in the opposite direction from the other 4 sectors and the Antarctic sea ice cover as a whole).

sea ice – climate change – satellite Earth observations – climate trends – Antarctic sea ice

Keywords: Climate change; Global Warming; Antarctica.

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Anatomy of a #glacial #meltwater discharge event in an #Antarctic cove (Phil Transact Roy Soc A., abstract)

[Source: Philosophical Transactions of the Royal Society A, full page: (LINK). Abstract, edited.]

Anatomy of a glacial meltwater discharge event in an Antarctic cove

Michael P. Meredith, Ulrike Falk, Anna Valeria Bers, Andreas Mackensen, Irene R. Schloss, Eduardo Ruiz Barlett, Kerstin Jerosch, Adrián Silva Busso, Doris Abele

Published 14 May 2018. DOI: 10.1098/rsta.2017.0163

 

Abstract

Glacial meltwater discharge from Antarctica is a key influence on the marine environment, impacting ocean circulation, sea level and productivity of the pelagic and benthic ecosystems. The responses elicited depend strongly on the characteristics of the meltwater releases, including timing, spatial structure and geochemical composition. Here we use isotopic tracers to reveal the time-varying pattern of meltwater during a discharge event from the Fourcade Glacier into Potter Cove, northern Antarctic Peninsula. The discharge is strongly dependent on local air temperature, and accumulates into an extremely thin, buoyant layer at the surface. This layer showed evidence of elevated turbidity, and responded rapidly to changes in atmospherically driven circulation to generate a strongly pulsed outflow from the cove to the broader ocean. These characteristics contrast with those further south along the Peninsula, where strong glacial frontal ablation is driven oceanographically by intrusions of warm deep waters from offshore. The Fourcade Glacier switched very recently to being land-terminating; if retreat rates elsewhere along the Peninsula remain high and glacier termini progress strongly landward, the structure and impact of the freshwater discharges are likely to increasingly resemble the patterns elucidated here.

This article is part of the theme issue ‘The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change’.

Keywords: Antarctica; Climate Change; Global Warming.

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#Icebergs, #sea #ice, blue #carbon and #Antarctic climate feedbacks (Phil Transact Roy Soc A, abstract)

[Source: Philosophical Transactions of the Royal Society A, full page: (LINK). Abstract, edited.]

Icebergs, sea ice, blue carbon and Antarctic climate feedbacks

David K. A. Barnes, Andrew Fleming, Chester J. Sands, Maria Liliana Quartino, Dolores Deregibus

Published 14 May 2018. DOI: 10.1098/rsta.2017.0176

 

Abstract

Sea ice, including icebergs, has a complex relationship with the carbon held within animals (blue carbon) in the polar regions. Sea-ice losses around West Antarctica’s continental shelf generate longer phytoplankton blooms but also make it a hotspot for coastal iceberg disturbance. This matters because in polar regions ice scour limits blue carbon storage ecosystem services, which work as a powerful negative feedback on climate change (less sea ice increases phytoplankton blooms, benthic growth, seabed carbon and sequestration). This resets benthic biota succession (maintaining regional biodiversity) and also fertilizes the ocean with nutrients, generating phytoplankton blooms, which cascade carbon capture into seabed storage and burial by benthos. Small icebergs scour coastal shallows, whereas giant icebergs ground deeper, offshore. Significant benthic communities establish where ice shelves have disintegrated (giant icebergs calving), and rapidly grow to accumulate blue carbon storage. When 5000 km2 giant icebergs calve, we estimate that they generate approximately 106 tonnes of immobilized zoobenthic carbon per year (t C yr−1). However, their collisions with the seabed crush and recycle vast benthic communities, costing an estimated 4 × 104 t C yr−1. We calculate that giant iceberg formation (ice shelf disintegration) has a net potential of approximately 106 t C yr−1 sequestration benefits as well as more widely known negative impacts.

This article is part of the theme issue ‘The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change’.

Keywords: Climate Change; Global Warming; Antarctica.

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#Avian #Influenza Virus #H5 Strain with North #American and #Eurasian #Lineage #Genes in an #Antarctic #Penguin (@CDC_EIDjournal, extract)

[Source: US Centers for Disease Control and Prevention (CDC), Emerging Infectious Diseases Journal, full page: (LINK). Extract, edited.]

Volume 22, Number 12—December 2016 / Letter

Avian Influenza Virus H5 Strain with North American and Eurasian Lineage Genes in an Antarctic Penguin

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To the Editor:

Previous studies have reported avian influenza virus (AIV)–positive serum samples obtained from Adélie (Pygoscelis adeliae), chinstrap (Pygoscelis antarcticus), and gentoo (Pygoscelis papua) penguins (1–4). Only recently was an H11N2 subtype virus isolated from Adélie penguins in Antarctica (5). We performed AIV surveillance in the Antarctic Peninsula to identify the strains currently circulating in different penguins species in this area.

(…)

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Suggested citation for this article: Barriga GP, Boric-Bargetto D, Cortez-San Martin M, Neira V, van Bakel H, et al. Avian influenza virus H5 strain with North American and Eurasian lineage genes in an Antarctic penguin [letter]. Emerg Infect Dis. 2016 Dec [date cited]. http://dx.doi.org/10.3201/eid2212.161076

DOI: 10.3201/eid2212.161076

Keywords: Research; Abstracts; Avian Influenza; H5; Penguins; Antarctica.

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Evidence for the #introduction, #reassortment and #persistence of diverse #influenza A viruses in #Antarctica (J Virol., abstract)

[Source: Journal of Virology, full page: (LINK). Abstract, edited.]

Evidence for the introduction, reassortment and persistence of diverse influenza A viruses in Antarctica

Aeron C. Hurt1,2⇑, Yvonne C. F. Su3, Malet Aban1, Heidi Peck1, Hilda Lau1, Chantal Baas1, Yi-Mo Deng1, Natalie Spirason1, Patrik Ellström4, Jorge Hernandez4,5, Bjorn Olsen6, Ian G. Barr1, Dhanasekaran Vijaykrishna3 and Daniel Gonzalez-Acuna7

Author Affiliations: 1WHO Collaborating Centre for Reference and Research on Influenza, North Melbourne, Victoria 3051, Australia. 2University of Melbourne, Melbourne School of Population and Global Health, Parkville, Victoria 3010, Australia. 3Program in Emerging Infectious Diseases, Duke-NUS Medical School, 8 College Road, Singapore 169857. 4Zoonosis Science Center, IMBIM, Uppsala University, Uppsala, Sweden. 5Department of Microbiology, Kalmar County Hospital, Kalmar, Sweden. 6Medical Sciences, Uppsala University, Uppsala, Sweden. 7Universidad de Concepción, Facultad de Ciencias Veterinarias, Chillán, Chile.

 

ABSTRACT

Avian influenza virus (AIV) surveillance in Antarctica during 2013 revealed the prevalence of evolutionarily distinct influenza viruses of H11N2 subtype in Adélie penguins. Here we present results from the continued surveillance of AIV on the Antarctic Peninsula during 2014 and 2015. In addition to the continued detection of H11 subtype viruses during 2014 in a snowy sheathbill, we isolated a novel H5N5 subtype virus during 2015 in a chinstrap penguin. Gene sequencing and phylogenetic analysis revealed that the H11 virus detected in 2014 had a >99.1% nucleotide similarity to the H11N2 viruses isolated in 2013, suggesting continued prevalence of this virus over multiple years in Antarctica. However, phylogenetic analysis of the H5N5 virus showed that their genome segments were recently introduced into the continent, except for the NP gene that was similar to that in the endemic H11N2 viruses. Our analysis indicates geographically diverse origins for the H5N5 virus genes; with the majority of its genome segments derived from North American lineage viruses, but the neuraminidase gene derived from a Eurasian lineage virus. In summary, we show the persistence of AIV lineages over multiple years in Antarctica; recent introduction of gene segments from diverse regions; and reassortment between different AIV lineages in Antarctica, which together, significantly increases our understanding of AIV ecology in this fragile and pristine environment.

 

IMPORTANCE

Analysis of avian influenza viruses (AIVs) detected in Antarctica reveals both the relatively recent introduction of an H5N5 AIV predominantly of North American-like origin, as well as the persistence of an evolutionarily divergent H11 AIV. These data demonstrate that the flow of viruses from North America may be more common than initially thought, and that once introduced, these AIVs have the potential to be maintained within Antarctica. The future introduction of AIVs from North America into the Antarctic Peninsula is of particular concern given that highly pathogenic H5Nx viruses have recently been circulating amongst wild birds in parts of Canada and the Unites States following the movement of these viruses from Eurasia via migratory birds. The introduction of a highly pathogenic influenza virus into penguin colonies within Antarctica might have devastating consequences.

 

FOOTNOTES

Corresponding author: Aeron C. Hurt, WHO Collaborating Centre for Reference and Research on Influenza, Victorian Infectious Diseases Reference Laboratory (VIDRL), Peter Doherty Institute, 792 Elizabeth St, Melbourne, Vic 3000, Australia, Ph: +61 3 9342 9314; Fax: +61 3 9342 9329; Email: aeron.hurt@influenzacentre.org

Copyright © 2016 Hurt et al.

This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license.

Keywords: Research; Abstracts; Avian Influenza; H5N5; H11N2; Wildbirds; Antarctica; Reassortant strains.

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#Antarctic #sea- #ice #expansion between 2000 and 2014 driven by tropical #Pacific decadal #climate variability (Nat Geo., abstract)

[Source: Nature Geoscience, full page: (LINK). Abstract, edited.]

Nature Geoscience | Letter

Antarctic sea-ice expansion between 2000 and 2014 driven by tropical Pacific decadal climate variability

Gerald A. Meehl, Julie M. Arblaster, Cecilia M. Bitz, Christine T. Y. Chung & Haiyan Teng

Nature Geoscience (2016) doi:10.1038/ngeo2751 Received 26 February 2016 Accepted 27 May 2016 Published online 04 July 2016

 

Abstract

Antarctic sea-ice extent has been slowly increasing in the satellite record that began in 19791, 2. Since the late 1990s, the increase has accelerated, but the average of all climate models shows a decline3. Meanwhile, the Interdecadal Pacific Oscillation, an internally generated mode of climate variability4, transitioned from positive to negative5, with an average cooling of tropical Pacific sea surface temperatures5, a slowdown of the global warming trend6, 7, 8 and a deepening of the Amundsen Sea Low near Antarctica1, 9, 10, 11, 12 that has contributed to regional circulation changes in the Ross Sea region and expansion of sea ice10. Here we show that the negative phase of the Interdecadal Pacific Oscillation in global coupled climate models is characterized by anomalies similar to the observed sea-level pressure and near-surface 850 hPa wind changes near Antarctica since 2000 that are conducive to expanding Antarctic sea-ice extent, particularly in the Ross Sea region in all seasons, involving a deepening of the Amundsen Sea Low. These atmospheric circulation changes are shown to be mainly driven by precipitation and convective heating anomalies related to the Interdecadal Pacific Oscillation in the equatorial eastern Pacific, with additional contributions from convective heating anomalies in the South Pacific convergence zone and tropical Atlantic regions.

Subject terms: Atmospheric dynamics  – Climate sciences  – Cryospheric science

Keywords: Research; Abstracts; Climate Change; Antarctica.

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