First-year land-fast Antarctic sea ice as an archive of ice
Details of Research
TitleFirst-year land-fast Antarctic sea ice as an archive of ice shelf meltwater fluxesAbstractSampling beneath Antarctic ice shelves is sparse; therefore, tracking changes in ocean Î´18O composition adjacent to ice shelves holds promise as an indicator of ice shelf basal melting. Sea ice archives of ice shelf-ocean interaction in particular could be important tools for future observational climate studies. Ocean Î´18O values near the McMurdo Ice Shelf were reconstructed using observational data (sea ice Î´18O, snow depth, and ice formation dates) from McMurdo Sound, Antarctica, by combining a recently revised version of an isotope fractionation model with an established thermodynamic sea ice model, resulting in improvements compared to previous approaches. Growth rates from the thermodynamic sea ice model were validated using direct growth rate measurements. That validation and supporting analysis indicated that a change was needed in ocean heat flux assumption from 0 W m-2 to around -13 W m-2 part way through the sea ice growth season. A well-constrained range (+1.84â€ Degrees to +2.21â€ Degrees) of effective fractionation coefficients for sea ice was derived, along with a mean of 1.99â€ Degrees. For the first time, reconstructed ocean Î´18O values were validated using winter-long measurements of Antarctic near-surface water Î´18O. Taking uncertainties into account, the reconstructed ocean Î´18O values generally agreed to within Â±0.2â€ Degrees with the measured ocean Î´18O mean values. Results indicated an overall decrease in measured ocean Î´18O during the winter, but this was not statistically significant given the uncertainties in the measurements. Although the method works, it currently has limited utility for determining the presence and scale of any step-changes in ocean Î´18O composition associated with present day ice shelf basal melting. This is because the uncertainty of the reconstructed values (Â±0.2â€ Degrees) is of the same magnitude as the expected change. Also, the requirement to parameterise the ocean heat flux is a barrier to the method being an entirely retrospective method (i.e., one requiring only data from the end of the sea ice growth season). In a future Antarctic scenario of increased basal melting of the ice shelves, the method may become more valuable in an Antarctic context. The method developed in this paper will be useful currently in the Arctic, because Arctic waters exhibit much larger fresh water fluxes. Copyright 2015 Elsevier B.V.AcknowledgementsCollection of the 2009 McMurdo Sound data was part of New ZealandÅ› contribution to the International Polar Year and was funded by the then Foundation for Research Science and Technology (FRST). The University of Otago, Industrial Research Ltd and the National Institute of Water and Atmospheric Research Ltd (NIWA) also provided financial and in-kind support. We are grateful to Antarctica New Zealand, the Scott Base 2009 winter team, Brian Staite, and Brett Grant for logistical and field support. Thanks to Myles Thayer, Richard Sparrow, and Peter Stroud for constructing instruments; Joe Trodahl, Daniel Pringle, Mike Williams, and Craig Stevens for advice; Russell Frew and Dianne Clark for isotope analysis; and Cecilia Bitz and Bill Lipscomb for making their code available via: http://www.atmos.washington.edu/Â bitz/column/.
1st AuthorSmith, I.AuthorSmith, I.Gough, A.Langhorne, P.Mahoney, A.Leonard, G.Van Hale, R.Jendersie, S.Haskell, T.Year2015JournalCold Regions Science and TechnologyVolume113Pages63-70DOI10.1016/j.coldregions.2015.01.007URLhttps://www.scopus.com/inward/recor.....2e4ff41cc053dbcb5e7812f9dKeywordsGrowth rateHeat fluxIsotopesMeltingOceanographySea iceSurface watersUncertainty analysis, Antarctic ice shelvesIce shelvesIce-ocean interactionsIsotope fractionationOxygen isotope fractionationsRetrospective methodSea ice formationsThermodynamic sea ice model, Ice, basal meltinggrowth rateheat fluxice shelfice-ocean interactionisotopic compositionisotopic fractionationmeltwateroxygen isotopesea icesurface water, AntarcticaEast AntarcticaMcMurdo Ice ShelfMcMurdo Sound, rank5Author KeywordsGrowth ratesIce shelf basal meltwaterIce-ocean interactionOxygen isotope fractionationSea ice formationSurface water isotope changes
TypeArticleCitationSmith, I., Gough, A., Langhorne, P., Mahoney, A., Leonard, G., Van Hale, R., Jendersie, S. and Haskell, T. (2015) First-year land-fast Antarctic sea ice as an archive of ice shelf meltwater fluxes. Cold Regions Science and Technology, 113: 63-70 doi:10.1016/j.coldregions.2015.01.007
Antarctica NZ (29th Nov 2018). First-year land-fast Antarctic sea ice as an archive of ice . In Website Antarctica NZ. Retrieved 24th Oct 2021 04:24, from https://adam.antarcticanz.govt.nz/nodes/view/63772