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Antarctic Peninsula warming triggers enhanced basal melt rates throughout West Antarctica.

ABSTRACT: The observed acceleration of ice shelf basal melt rates throughout West Antarctica could destabilize continental ice sheets and markedly increase global sea level. Explanations for decadal-scale melt intensification have focused on processes local to shelf seas surrounding the ice shelves. A suite of process-based model experiments, guided by CMIP6 forcing scenarios, show that freshwater forcing from the Antarctic Peninsula, propagated between marginal seas by a coastal boundary current, causes enhanced melting throughout West Antarctica. The freshwater anomaly stratifies the ocean in front of the ice shelves and modifies vertical and lateral heat fluxes, enhancing heat transport into ice shelf cavities and increasing basal melt. Increased glacial runoff at the Antarctic Peninsula, one of the first signatures of a warming climate in Antarctica, emerges as a key trigger for increased ice shelf melt rates in the Amundsen and Bellingshausen Seas.

SUBMITTER: Flexas MM

PROVIDER: S-EPMC9374342 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature

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Antarctic Peninsula warming triggers enhanced basal melt rates throughout West Antarctica.

Flexas M Mar MM Thompson Andrew F AF Schodlok Michael P MP Zhang Hong H Speer Kevin K

Science advances 20220812 32

The observed acceleration of ice shelf basal melt rates throughout West Antarctica could destabilize continental ice sheets and markedly increase global sea level. Explanations for decadal-scale melt intensification have focused on processes local to shelf seas surrounding the ice shelves. A suite of process-based model experiments, guided by CMIP6 forcing scenarios, show that freshwater forcing from the Antarctic Peninsula, propagated between marginal seas by a coastal boundary current, causes ...[more]

PMID: 35960791

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Project description:Glacio-marine fjords occur widely at high latitudes and have been extensively studied in the Arctic, where heavy meltwater inputs and sedimentation yield low benthic faunal abundance and biodiversity in inner-middle fjords. Fjord benthic ecosystems remain poorly studied in the subpolar Antarctic, including those in extensive fjords along the West Antarctic Peninsula (WAP). Here we test ecosystem predictions from Arctic fjords on three subpolar, glacio-marine fjords along the WAP. With seafloor photographic surveys we evaluate benthic megafaunal abundance, community structure, and species diversity, as well as the abundance of demersal nekton and macroalgal detritus, in soft-sediment basins of Andvord, Flandres and Barilari Bays at depths of 436-725 m. We then contrast these fjord sites with three open shelf stations of similar depths. Contrary to Arctic predictions, WAP fjord basins exhibited 3 to 38-fold greater benthic megafaunal abundance than the open shelf, and local species diversity and trophic complexity remained high from outer to inner fjord basins. Furthermore, WAP fjords contained distinct species composition, substantially contributing to beta and gamma diversity at 400-700 m depths along the WAP. The abundance of demersal nekton and macroalgal detritus was also substantially higher in WAP fjords compared to the open shelf. We conclude that WAP fjords are important hotspots of benthic abundance and biodiversity as a consequence of weak meltwater influences, low sedimentation disturbance, and high, varied food inputs. We postulate that WAP fjords differ markedly from their Arctic counterparts because they are in earlier stages of climate warming, and that rapid warming along the WAP will increase meltwater and sediment inputs, deleteriously impacting these biodiversity hotspots. Because WAP fjords also provide important habitat and foraging areas for Antarctic krill and baleen whales, there is an urgent need to develop better understanding of the structure, dynamics and climate-sensitivity of WAP subpolar fjord ecosystems.

Project description:BackgroundThe west Antarctic Peninsula (WAP) is a region of rapid environmental changes, with regional differences in climate warming along the north-south axis of the peninsula. Along the WAP, Palmer corresponds to a warmer region with lesser sea ice extent in the north compared to Rothera ~ 400 km to the south. Comprehensive and comparative, year-round assessments of the WAP microbial community dynamics in coastal surface waters at these two locations are imperative to understand the effects of regional climate warming variations on microbial community dynamics, but this is still lacking.ResultsWe report on the seasonal diversity, taxonomic overview, as well as predicted inter-and intra-domain causal effects (interactions) of the bacterial and microbial eukaryotic communities close to the Palmer station and at the Rothera time-series site between July 2013 and April 2014. Our 16S- and 18S-rRNA gene amplicon sequencing data showed that across all seasons, both bacteria and microbial eukaryotic communities were considerably different between the two sites which could be attributed to seawater temperature, and sea ice coverage in combination with sea ice type differences. Overall, in terms of biotic drivers, causal-effect modelling suggests that bacteria were stronger drivers of ecosystem dynamics at Palmer, while microbial eukaryotes played a stronger role at Rothera. The parasitic taxa Syndiniales persevered at both sites across the seasons, with Palmer and Rothera harbouring different key groups. Up to 62.3% of the negative causal effects were driven by Syndiniales at Rothera compared to only 13.5% at Palmer, suggesting that parasitism drives community dynamics at Rothera more strongly than at Palmer. Conversely, SAR11 Clade II, which was less abundant but persistent year-round at both sites, was the dominant driver at Palmer, evidenced by many (28.2% and 37.4% of positive and negative effects respectively) strong causal effects. Article note: Kindly check first page article notes are correct.ConclusionsOur research has shed light on the dynamics of microbial community composition and correlative interactions at two sampling locations that represent different climate regimes along the WAP.

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Antarctic Peninsula warming triggers enhanced basal melt rates throughout West Antarctica.

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Antarctic Peninsula warming triggers enhanced basal melt rates throughout West Antarctica.

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