This data set represents the model results plotted in the figures in Bett et al. (2024), produced using the MITgcm/WAVI ice/ocean coupled model. The model domain is the Amundsen Sea sector, where the simulations start in approximately the year 2015 and run for 180 years. Simulations are forced using idealised ocean boundary conditions which represent cold and warm conditions, along with a third extreme case where no ice shelf melting is applied. These simulations were produced in order to examine the ice/ocean processes that occur during future evolution of the region. For full descriptions of the results plotted in each figure see Bett et al. (2024). Funding was provided by NERC Grant NE/S010475/1, ITGC THWAITES MELT (NE/S006656/1), ITGC THWAITES PROPHET (NE/S006796/1) and the European Union''s Horizon 2020 grant PROTECT (869304).

Marine debris washed up on beaches on Goudier Island has been recorded since 2014. Surveys are conducted on a monthly basis when the station is occupied during the summer season. This data contributes to the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) Marine Debris programme.

The data include size, sex, location and morphological measurements and of Muraenolepis specimens included in Fitzcharles et al. (2021). The morphometric data were primarily collected from fish captured during South Georgia Groundfish Surveys in 2003, 2004 and 2005, with additional data obtained from type specimens and extracted from published descriptions of Muraenolepididae. For genetic studies, tissue samples from the South Georgia specimens were supplemented by additional tissue samples from Muraenolepis in other parts of the Southern Ocean. Source, location and depth of capture are included for all specimens that were sequenced, together with sequence Accession Numbers (to the DNA Database of Japan) for Cox 1 and 16S rRNA sequences. The work was primarily funded by the Government of South Georgia & the South Sandwich Islands and was a component part of Elaine Fitzcharles'' PhD (University of St Andrews).

Temperature data were collected from a tidepool at Rothera Point, Antarctica every two minutes from February 1999 to May 2000, with the aim of documenting tidal, diurnal and seasonal variability.

This dataset is referring to 2-year time series of particle flux, as measured by two deep moored sediment traps (P2, P3) located in the Southern Ocean (northern Scotia Sea sector), a globally important region of atmospheric CO2 drawdown containing both naturally iron-fertilised (P3) and iron-limited (P2) regimes. The dataset includes the main biogeochemical flux parameters (such as Bsi, POC and PIC) as well as the specific contribution of each part of the plankton calcifying community (pteropods, foraminifera, coccolithphores and ostracods) to the PIC within a period from April 2009 to February 2011. The dataset allows the estimation of the Carbonate Counter Pump (CCP), which causes an increase in surface ocean CO2 through the calcification and precipitation of carbonate.

These data are gonad index (gonad mass/total animal mass) and egg size measurements for two Antarctic marine invertebrates, the starfish Odontaster validus and the brittle star Ophionotus victoriae. Data are for samples hand-collected monthly, where weather permits, by scuba divers from sites near the British Antarctic Survey''s research station at Rothera Point, Adelaide Island. Samples were first collected in 1997 and have continued for 19 years to 2015.

Benthic Macrofaunal abundance and biomass data collected during a series of ship-board sampling campaigns in the Barents Sea. As part of the NERC funded Changing Arctic Ocean programme, in July of 2017, 2018 and 2019, the RSS James Clark Ross followed a North-South transect at 30 degrees Longitude. In 2017 six stations were sampled (B3, B13, B14, B15, B16, B17); in 2018 seven stations were sampled (B3, B13, B14, Xs, B15, B16, B17); and in 2019 five stations were sampled (B3, B13, B14, B15, B16). Macrofaunal samples were collected using a USNL corer (surface area 0.1m<sup>2</sup>). On recovery all faunal samples were fixed and preserved with 10% buffered formaldehyde solution. The faunal samples were transported to Plymouth Marine Laboratory where the fauna were extracted, identified to species level where possible using the most up to date literature available, and biomassed (blotted wet weight) to species level. A reference collection has been created containing an example of each taxon to ensure maximum quality control was maintained by the three analysts that conducted the species identification and for subsequent cruise data generated. Funded by the NERC Changing Arctic Ocean Seafloor (ChAOS).

Autosub Long Range (ALR) was deployed along the Modified Warm Deep Water Inflow beneath Ronne Ice Shelf in February 2018 as part of the Ice shelves in a warming world: Filchner Ice Shelf system large grant, Antarctica. The vehicle was equipped with a Seabird Conductivity-Temperature-Depth (CTD) sensor, two Teledyne Acoustic Doppler Current Profilers (ADCPs), one upward looking and one downward looking, and a nose-mounted Rockland Scientific International MicroRider turbulence package. ALR followed a rhumb line course beneath the ice shelf, running approximately parallel to the 400 m isobath. The vehicle alternated between stretches of bottom tracking and top tracking in a square-wave pattern, while maintaining a minimum clearance of 80 m between the vehicle and the ice base or seabed. Funding was provided by the UK Natural Environment Research Council Large Grant Ice shelves in a warming world: Filchner Ice Shelf system, Antarctica (Grant No. NE/L013770/1).

UTLs were used to determine whether whole animal acclimation had occurred in R. perrieri on heated settlement panels in the Antarctic. The panels were placed at 15m depth at two sites (South Cove and North Cove) near Rothera Research Station, Adelaide Island, Antarctic Peninsula (67.06861 S, 68.125 W). Heated and non-heated panels (one each of control, +1, +2) from the South Cove and North Cove sites colonised by R. perrieri were transferred to a 60 L jacketed tank with aerated sea water at the same temperature as the ambient sea water (0 degrees Celsius) and connected to a thermocirculator (Grant Instruments Ltd, Cambridge, UK). The temperature was raised at 1 degree Celsius h-1 with the temperature limit of each animal noted when they no longer responded to tactile stimuli. Funding was provided by the NERC grant NE/J007501/1.

This dataset contains processed acoustic backscatter data that reflect integrated density estimates for Antarctic krill (Euphausia superba). The acoustic backscatter data are from the Western Core Box (WCB), comprising 8 acoustic transects that span the shelf-break at South Georgia. The data were obtained from a time series of 22 cruises carried out between 1996/97 and 2019/20. Data were collected using either a Simrad EK500 or EK60 echo sounder by biological oceanographers working at the British Antarctic Survey under the Ecosystems scientific research programme and predecessor Discovery 2010 and Dynamo research programmes. Funding was provided by the NERC/BAS Antarctic, Logistic, Infrastructure (ALI) Science and predecessor Long Term Monitoring Science research programmes.