A journey through a sub-Antarctic island fjord from glacier retreat to fisheries management

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• Jo Zanker (Northumbria University)
• Tuesday 17 September 2024, 14:00-15:00
• BAS Seminar Room 1; https://ukri.zoom.us/j/92840831145.

If you have a question about this talk, please contact Dr Birgit Rogalla.

For any external attendees, please email Birgit Rogalla (birgal at bas.ac.uk) and Yohei Takano (yokano at bas.ac.uk) to arrange for access to BAS .

Climate change is impacting high-latitude fjord circulation with consequences for the melting of marine-terminating glaciers and for the transport of biological material essential for supporting local ecosystems. Currently, little is understood about oceanographic variability in sub-Antarctic island fjords such as Cumberland Bay, the largest fjord on the island of South Georgia in the Southern Ocean. Cumberland Bay is split into two arms, West Bay and East Bay, each with a large marine-terminating glacier at the head. These glaciers have shown asymmetrical retreat rates over the past century, and it is not yet understood why. With a combination of oceanographic data and the development of a new high-resolution hydrodynamic model we gain the first understanding of the drivers of temporal and spatial oceanographic variability and elucidate the role of such variability in the rate of glacier retreat. We find the possible presence of a shallow inner sill, and the occurrence of foehn winds to both be potentially contributing to rapid glacier retreat. The model provides a tool for exploring oceanographic influences on larval retention for the ecologically and commercially important mackerel icefish. Using model flow fields to drive an individual-based model parameterised for mackerel icefish larvae spawned in Cumberland Bay, we identify West Bay as a key retention zone and highlight how larval retention is sensitive to the complex fjord circulation patterns driven by winds, freshwater and fjord-shelf exchanges. Physical processes linked to climate change are found to influence chances of successful retention, which underpins their future ability to recruit to adult stock.

This talk is part of the British Antarctic Survey - Polar Oceans seminar series series.

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