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Bentley, M. J., Ocofaigh, C., Anderson, J. B., Conway, H., Davies, B., Graham, A. G. C., Hillenbrand, C. D., Hodgson, D. A., Jamieson, S. S. R., Larter, R. D., Mackintosh, A., Smith, J. A., Verleyen, E., Ackert, R. P., Bart, P. J., Berg, S., Brunstein, D., Canals, M., Colhoun, E. A., Crosta, X., Dickens, W. A., Domack, E., Dowdeswell, J. A., Dunbar, R., Ehrmann, W., Evans, J., Favier, V., Fink, D., Fogwill, C. J., Glasser, N. F., Gohl, K., Golledge, N. R., Goodwin, I., Gore, D. B., Greenwood, S. L., Hall, B. L., Hall, K., Hedding, D. W., Hein, A. S., Hocking, E. P., Jakobsson, M., Johnson, J. S., Jomelli, V., Jones, R. S., Klages, J. P., Kristoffersen, Y., Kuhn, G., Leventer, A., Licht, K., Lilly, K., Lindow, J., Livingstone, S. J., Mass?, G., McGlone, M. S., McKay, R. M., Melles, M., Miura, H., Mulvaney, R., Nel, W., Nitsche, F. O., O'Brien, P. E., Post, A. L., Roberts, S. J., Saunders, K. M., Selkirk, P. M., Simms, A. R., Spiegel, C., Stolldorf, T. D., Sugden, D. E., van der Putten, N., van Ommen, T., Verfaillie, D., Vyverman, W., Wagner, B., White, D. A., Witus, A. E. Zwartz, D. (2014). A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum. Quaternary Science Reviews, 100, 1-9.A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20 ka, 15 ka, 10 ka and 5 ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse la. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorities for future work. The synthesis is intended to be a resource for the modelling and glacial geological community. (C) 2014 The Authors. Published by Elsevier Ltd.publishersversionPeer reviewe

Editor: H. ElderfieldKeywords: highly branched isoprenoid alkenes sea ice Iceland sediments A high resolution account of Icelandic sea ice over the last millennium has been constructed using a novel proxy based on the presence in sediments of a biomarker (IP 25 ) produced by sea ice algae. Comparison with historical sea ice records demonstrates a strong correlation between documented sea ice occurrences and the IP 25 proxy. An excellent agreement is also observed between the IP 25 record and a diatom-based sea surface temperature reconstruction obtained from the same core and the Crowley and Lowery Northern Hemisphere temperature reconstruction. Using this approach, we provide new historical sea ice data for periods where records are scarce or absent and evidence for abrupt changes to sea ice and/or climate conditions around Iceland during the Little Ice Age.

Sea ice is a critical component of the climate system: variations in sea-ice cover affect the albedo of polar regions, and also the rate of deepwater formation 1,2 . Changes in the sea-ice cover of the North Atlantic Ocean are thought to have been related to abrupt climate changes throughout the last glacial termination 3 , but reconstructions of sea-ice conditions are rare. Here we use the sedimentary abundance of the IP 25 and brassicasterol biomarkers, produced by sea-ice-associated diatoms and open-water phytoplankton, respectively, to generate a record of sea-ice conditions in the northernmost Atlantic Ocean for the past 30,000 years. Our reconstruction shows that a stationary margin between sea-ice cover and the open ocean existed during the Last Glacial, although perennial sea-ice cover prevailed for most of the Last Glacial Maximum. An early warming about 14,000 years ago was associated with ice-free conditions; however, seasonal sea ice was present throughout the Holocene. We find temporal links between our record of sea ice and reconstructions of the amount of relatively warm Atlantic water advected into the Nordic Seas 4,5 . We therefore conclude that changes in sea-ice conditions are linked to regional and global climate anomalies and oceanographic circulation in the North Atlantic.The distribution of sea ice in Fram Strait, the only deepwater connection (∼2,600 m mean water depth) between the Arctic and Atlantic oceans, is mainly controlled by the inflow of temperate water from the North Atlantic along the western continental margin of Spitsbergen through the Norwegian and West Spitsbergen currents 1 . In contrast, the East Greenland current carries cold water (and sea ice) southward through this gateway 1 (Fig. 1). The relative contributions of these currents strongly influence the thermohaline circulation, thus contributing to global climate 1 .Previously, it has been shown that, when detected in marine sediments, a C 25 isoprenoid lipid (IP 25 ) biosynthesized by Arctic sea-ice diatoms acts as a proxy for previous spring sea-ice occurrence and subsequent melt 6,7 , whereas the phytoplanktonderived sterol brassicasterol, reflects open-ocean conditions during summer 8 . In the current study, we present organic carbon 9 (global productivity and terrigenous organic carbon input) and fluxes of IP 25 (sea ice) and brassicasterol (phytoplankton; ref. 9) for a sediment core (PS2837-5) from the western flank of the Yermak Plateau (81 • 13.99 N, 02 • 22.85 E, northwest of Spitsbergen, 1,042 m water depth; ref. 10) close to the present-day summer sea-ice margin in Fram Strait (Fig. 1). We use the previously reported age model of PS2837-5, which is based on 14 accelerator mass spectrometry 14 C ages of tests of the planktic foraminifer Neogloboquadrina pachyderma sin. and assumes a marine-reservoir correction of 400 years and linear interpolation between 14 C-dated horizons 11 . In the following, ages are given in calibrated calendar years before present. For much of the interval between 30 and 17 kyr bp (La...

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