Antarctic climate variability at regional and continental scales over
the last 2,000 years
Barbara Stenni1,2, Mark A. J. Curran3,4, Nerilie J. Abram5,6, Anais Orsi7, Sentia Goursaud7,8, Valerie Masson-Delmotte7, Raphael Neukom9, Hugues Goosse10, Dmitry Divine11,12, Tas van Ommen3,4, Eric J. Steig13, Daniel A. Dixon14, Elisabeth R. Thomas15, Nancy A. N. Bertler16,17, Elisabeth Isaksson11, Alexey Ekaykin18,19, Massimo Frezzotti20, and Martin Werner211Department of Environmental Sciences, Informatics and Statistics, Ca’ Foscari University of Venice, Italy 2Institute for the Dynamics of Environmental Processes, CNR, Venice, Italy 3Australian Antarctic Division, 203 Channel Highway, Kingston Tasmania 7050, Australia 4Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Hobart 7001, Australia 5Research School of Earth Sciences, Australian National University, Canberra ACT 2601, Australia 6ARC Centre of Excellence for Climate System Science, Australian National University, Canberra ACT 2601, Australia 7Laboratoire des Sciences du Climat et de l’Environnement (IPSL/CEA-CNRS-UVSQ UMR 8212), CEA Saclay, 91191 Gifsur-Yvette cédex, France 8Université Grenoble Alpes, Laboratoire de Glaciologie et Géophysique de l’Environnement (LGGE), 38041 Grenoble, France 9University of Bern, Oeschger Centre for Climate Change Research & Institute of Geography, 3012 Bern, Switzerland 10Université catholique de Louvain, Earth and Life Institute, Centre de recherches sur la terre et le climat Georges Lemaître, B-1348 Louvain-la-Neuve, Belgium 11Norwegian Polar Institute, Fram centre, N-9296 Tromsø, Norway 12Department of Mathematics and Statistics, Faculty of Science, University of Tromsø - The Arctic University of Norway, N-9037, Norway 13Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA 14Climate Change Institute, University of Maine, Orono, ME 04469, USA 15British Antarctic Survey, Cambridge, UK CB3 0ET 16Antarctic Research Centre, Victoria University of Wellington, Wellington 6012, New Zealand 17National Ice Core Research Facility, GNS Science, Gracefield 5040, New Zealand 18Arctic and Antarctic Research Institute, St Petersburg, Russia 19Institute of Earth Sciences, Saint Petersburg State University, St Petersburg, Russia 20ENEA Casaccia, Rome, Italy 21Alfred Wegner Institute, Helmholtz Centre for Polar and Marine Research, 27570 Bremerhaven, Germany
Received: 28 Feb 2017 – Accepted for review: 13 Mar 2017 – Discussion started: 22 Mar 2017
Abstract. Climate trends in the Antarctic region remain poorly characterised, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica 2k working group, we build an enlarged database of ice core water stable isotope records from Antarctica, consisting of 112 records. We produce both unweighted and weighted isotopic (δ18O) composites and temperature reconstructions since 0 CE, binned at 5 and 10-year resolution, for 7 climatically-distinct regions covering the Antarctic continent. Following earlier work of the Antarctica 2k working group, we also produce composites and reconstructions for the broader regions of East Antarctica, West Antarctica, and the whole continent. We use three methods for our temperature reconstructions: i) a temperature scaling based on the δ18O-temperature relationship output from an ECHAM5-wiso model simulation nudged to ERA-interim atmospheric reanalyses from 1979 to 2013, and adjusted for the West Antarctic Ice Sheet region to borehole temperature data; ii) a temperature scaling of the isotopic normalized anomalies to the variance of the regional reanalysis temperature and iii) a composite-plus-scaling approach used in a previous continental scale reconstruction of Antarctic temperature since 1 CE but applied to the new Antarctic ice core database. Our new reconstructions confirm a significant cooling trend from 0 to 1900 CE across all Antarctic regions where records extend back into the 1st millennium, with the exception of the Wilkes Land coast and Weddell Sea coast regions. Within this long-term cooling trend from 0–1900 CE we find that the warmest period occurs between 300 and 1000 CE, and the coldest interval from 1200 to 1900 CE. Since 1900 CE, significant warming trends are identified for the West Antarctic Ice Sheet, the Dronning Maud Land coast and the Antarctic Peninsula regions, and these trends are robust across the distribution of records that contribute to the unweighted isotopic composites and also significant in the weighted temperature reconstructions. Only for the Antarctic Peninsula is this most recent century-scale trend unusual in the context of natural variability over the last 2000-years. However, projected warming of the Antarctic continent during the 21st Century may soon see significant and unusual warming develop across other parts of the Antarctic continent. The extended Antarctica 2k ice core isotope database developed by this working group opens up many avenues for developing a deeper understanding of the response of Antarctic climate to natural and anthropogenic climate forcings. The first long-term quantification of regional climate in Antarctica presented herein is a basis for data-model comparison and assessments of past, present and future driving factors of Antarctic climate.
Stenni, B., Curran, M. A. J., Abram, N. J., Orsi, A., Goursaud, S., Masson-Delmotte, V., Neukom, R., Goosse, H., Divine, D., van Ommen, T., Steig, E. J., Dixon, D. A., Thomas, E. R., Bertler, N. A. N., Isaksson, E., Ekaykin, A., Frezzotti, M., and Werner, M.: Antarctic climate variability at regional and continental scales over
the last 2,000 years, Clim. Past Discuss., doi:10.5194/cp-2017-40, in review, 2017.