Physical, biogeochemical and ecological impacts of giant icebergs: a multidisciplinary study of iceberg A68 near South Georgia, Southern Ocean  

• DOI: 10.5194/egusphere-egu22-3914
• Publication Date: 2022-03-27T19:18:47Z
• Authors: Natasha Lucas; Alexander Brearley; Povl Abrahamsen; Michael Meredith; Katherine Hendry; Clara Manno; Cecilia Liszka; Laura Gerrish; Andrew Shepherd; Anne Braakmann-Fo...; Andrew Fleming; Norman Ratcliffe; Martin Collins; Eugene Murphy; David Barnes; Geraint Tarling
• Keywords: Iceberg; Biogeochemical Cycle; Marine ecosystem

<p>Giant icebergs can greatly impact the mass, freshwater and nutrient budgets of ocean. They deposit large amounts at great distances from their origins, impacting upper-ocean stratification mixing, they be important vectors for micronutrient delivery with impacts on primary production carbon drawdown. Their advection, productivity blocking flows critical zooplankton regional ecosystem functioning, consequences higher trophic levels local fisheries. breakouts ice shelves create new opportunities biological colonisation sinks collisions seabed (iceberg scour) shape benthic biodiversity patterns influence sequestration.</p><p>In 2017, A68 iceberg (around 6000 km<sup>2</sup>) calved Larsen C Ice Shelf Antarctic Peninsula. It subsequently moved eastward northward, crossing Scotia Sea to move, virtually intact, within 300 km island South Georgia (SG) in late 2020. This caused concern, following a previous iceberg, A38, SG 2003-2004. Further, given advances observing technology since time it afforded an unparalleled opportunity study detail giant bergs ocean physical, biogeochemical systems.</p><p>Diverse datasets were collected response this event. A research cruise RRS James Cook was mobilised, as approached fragmented into multiple smaller pieces. These measurements included physical parameters (including oxygen isotopes inform sources), dissolved inorganic nutrients, biosilica concentration, composition phytoplankton community bloom dynamics by input terrigenous material. Ocean gliders, deployed ship, surveyed largest fragment extremely close proximity followed remainder its life, deconvolving frontal assisting understanding meltwater influence. Concurrently, Earth Observation (EO) techniques employed including Sentinel-1 SAR imagery, Planet Labs very high-resolution optical MODIS Aqua Terra imagery satellite radar laser altimetry. sediment trap mooring downstream will utilised investigate export period that 10 years while enhanced observations predator colonies compare foraging paths breeding performance those years.</p><p>This presentation discuss preliminary findings A68, EO-derived quantifications changing morphology, loss fragmentation basal melting, significance fractures dictating collapse fissures. Physical oceanographic data ship gliders are used determine water column stability, mixing circulation range scales. Biogeochemical reveal interacting processes biomass species composition. Ecosystem implications future directions investigation outlined.</p><p> </p>