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From Fabio Florindo and Martin Siegert, Concluding Remarks: Recent Changes in Antarctica and FutureResearch. In: Fabio Florindo and Martin Siegert, editors: Developments in Earth and EnvironmentalSciences, Vol 8, Antarctic Climate Evolution, Fabio Florindo and Martin Siegert. The Netherlands:

Elsevier, 2009, pp. 571–576.ISBN: 978-0-444-52847-6

r Copyright 2009 Elsevier BV.Elsevier

Provided for non-commercial research and educational use only.

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Author's personal copy

Developments in Earth & Environmental Sciences, 8F. Florindo and M. Siegert (Editors)r 2009 Elsevier B.V. All rights reservedDOI 10.1016/S1571-9197(08)00013-X

Chapter 13

Concluding Remarks: Recent Changes inAntarctica and Future Research

Fabio Florindo1,� and Martin Siegert2

1Istituto Nazionale di Geofisica e Vulcanologia, via di Vigna Murata 605,00143 Roma, Italy2School of GeoSciences, Grant Institute, University of Edinburgh, The King’sBuildings, West Mains Road, Edinburgh EH9 3JW, UK

ABSTRACT

Antarctic Climate Evolution has been, and will be, hugely influential in thedevelopment of Earth’s environment. This book has detailed how Antarcticachanged during several key stages in the Cenozoic. Here we take stock of pastchanges and consider how they may be helpful in evaluating future changes inAntarctica.

Warming of the climate system is unequivocal, as is now evident fromobservations of increases in global average air and ocean temperatures,widespread melting of snow and ice in Greenland and in the AntarcticPeninsula, and rising global sea levels. Eleven of the 12 years between 1995and 2006 are among the 12 warmest years in the instrumental record since1850 (IPCC, 2007). According to the latest IPCC worst-case scenarioprojections (i.e. continued greenhouse gas emissions at or above currentrates), global annual mean temperatures by 2100 are likely to exceed thosethat have been experienced by the Earth in the last 40myr, that is before theAntarctic Ice Sheet first developed (IPCC, 2007). If warming continues, theimplication is that ice loss to the ocean may far outweigh gain from iceaccumulation, with huge implications for global sea level (and associated

E-mail: florindo@ingv.it (F. Florindo).

�Corresponding author. Tel.: þ39 0651860 383; Fax: þ39 0651860 397;

Figure 13.1: Ice-sheet surface elevation changes, recorded by satellitealtimetric measurements, between 1992 and 2003. Note how ice loss isconcentrated at the margins of ice streams in the Amundsen Bay region ofEast Antarctica, and the Totten and Cook glaciers in East Antarctica. Theseregions of ice loss are characterised by ice resting on a bed suppressed severalhundred metres below sea-level, implying an ice-ocean connection to thecurrent retreat (from Shepherd and Wingham (2007), with permission of

the authors).

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major changes in coastlines and the inundation of low-lying areas),atmospheric composition and dynamics, and ocean circulation.Recent comprehensive, and near continuous, satellite altimetric observa-

tions indicate that the Antarctic Ice Sheet is losing mass, and that the rate ofloss has increased steadily during the last few decades (Fig. 13.1, e.g. Daviset al., 2005; Shepherd and Wingham, 2007; Rignot et al., 2008). Most loss isfrom the West Antarctic Ice Sheet (WAIS), especially along the Belling-shausen and Amundsen seas (132760Gt yr�1 in 2006). During the past ca.40 years many glaciers, and a series of ice-shelves, have retreated in theAntarctic Peninsula (e.g. Cook et al., 2005) and, since the new millennium,two large ice shelves, located either side of the Antarctic Peninsula (theLarsen B and Wilkins ice shelves, with extents of 3,250 km2 and over570 km2, respectively; Fig. 13.2), have suddenly broken up in dramaticfashion and separated from the continent. The decay of these ice shelves willnot have affected sea level because ice shelves are afloat and thus alreadydisplacing their weight of water. However, ice-shelf decay has the potentialto greatly reduce buttressing forces on grounded ice that resist the flow fromthe continent to the ocean. In other words, ice-shelf decay may encouragefurther loss of grounded ice, which will affect global sea level. A number offactors contribute to ice-shelf collapse, including atmospheric and oceanic

Figure 13.2: High-resolution, enhanced-colour image of the Wilkins IceShelf in Antarctica, taken on 8 March 2008 by Taiwan’s Formosat-2 satellite(Credit: left, National Snow and Ice Data Center; right, National Snow andIce Data Center/Courtesy Cheng-Chien Liu, National Cheng Kung University(NCKU), Taiwan and Taiwan’s National Space Organization (NSPO);processed at Earth Dynamic System Research Center at NCKU, Taiwan).

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temperatures. If these continue to rise, we may see more ice shelves decayingacross the Antarctic Peninsula and elsewhere in Antarctica (e.g. Morris andVaughan, 2003; MacAyeal and others, 2006; Glasser and Scambos, 2008).It is worth noting that, over the past 50 years, the western part of theAntarctic Peninsula has experienced the greatest temperature increase onEarth, rising by nearly 31C (e.g. King et al., 2003; Turner et al., 2005). Thisis approximately 10 times the mean rate of global warming, as reported bythe IPCC.The temperature increase is not confined to the Antarctic Peninsula; it is

also occurring in and over the oceans surrounding Antarctica. For example,it is now well-established that the waters of the Antarctic CircumpolarCurrent (ACC) are warming more rapidly than the global ocean as a whole.A comparison of temperature measurements from the 1990s with data fromearlier decades shows a large-scale warming of around 0.21C in the ACCwaters at around 700–1,100m depth (Gille, 2002).Across the East Antarctica Ice Sheet (EAIS) the mass balance is near a

steady state with the flow of ice. Its interior is increasing in overall thickness,which is probably the result of increased ice accumulation due to warmer(and moister) atmospheric conditions over the continental interior (Churchet al., 2001). This mass gain is balanced by ice thinning/loss across thepotentially dynamic marine sectors in Wilkes Land (Davis et al., 2005).Further atmospheric and ocean warming may be incompatible with

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sustaining mass balance in this region, implying it too is susceptible tofurther changes in a warming world. A greater understanding of past changesin this region of East Antarctica is clearly warranted.Comprehending glacial history since the Last Glacial Maximum (LGM),

which culminated around 20,000 years ago, is also critical to knowingwhether recent changes are a result of human activities and/or a result of ice-sheet relaxation since the LGM. The geological record tells us that theWAIS retreat occurred during the Holocene, far later than NorthernHemisphere ice sheets. It is certainly possible that changes observed in somelocations today can be at least part explained by post-LGM ice retreat to amore stable interglacial condition. Geological evidence on the rate of ice losssince the LGM is therefore needed at several sites across the Antarcticcontinent.Understanding Antarctic climate evolution requires continent-wide as well

as continent-to-deep-sea studies of past climate records, to decipher theirseparate but related histories. Some of these activities are long-termundertakings but commitment within the frame of IPY is essential to layingthe groundwork for long-term success. Over the next few years ACE aimsto integrate geoscience data provided by sediment cores (ANDRILL,andrill.org; SHALDRILL, www.shaldril.rice.edu; IODP, www.iodp.org) andice cores (EPICA, www.esf.org; ITASE, www2.umaine.edu/itase/; TAL-DICE; WAIS Divide, www.waisdivide.unh.edu/) with the new generation ofclimate models that couple atmosphere, ocean, ice sheet and sedimentmodelling on key time periods from the distant past (i.e. tens of millions ofyears ago when global temperature was several degrees warmer than today) tothe recent past (i.e. during the Holocene, prior to anthropogenic impacts aswell as at the LGM). Acquisition of sedimentary records from the floors ofsubglacial lakes is also anticipated in the next few years. Such informationmay inform us about ice-sheet histories, and when West Antarctica was lastdeglaciated. Drilling, sampling and studying subglacial lakes remotely andwithout causing their contamination represent a considerable technologicalchallenge. In this regard the exploration of sub-ice lakes represents a goodanalogue for the exploration of planets and satellites such as Europa.A number of subglacial lakes have been identified in Antarctica and, of these,one subglacial lake in West Antarctica, named Lake Ellsworth (from theAmerican explorer Lincoln Ellsworth), is well suited to exploratory research(www.geos.ed.ac.uk/ellsworth).This book has demonstrated that the Antarctic Ice Sheet has undergone

many changes, and has varied in size considerably over the Cenozoic. Thenature of these changes has been shown to be associated with global climateconditions, forced externally or through interaction with ice and climate

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conditions in Antarctica and the Southern Ocean. IPCC predictions ofatmospheric greenhouse gases are pertinent to future ice volumes inAntarctica. If such gases continue to rise, in a few centuries time the valueof atmospheric carbon dioxide may be greater than at any time in theCenozoic. The obvious danger is that, in a warming world, the Antarctic IceSheet may respond to climate and ocean changes as it has done in the past. Inother words, the palaeo-ice-sheet reconstructions highlighted in this bookmay be relevant to assessments of future changes in Antarctica.Over the next decade, ACE will be pursuing a broad range of objectives to

better comprehend past Antarctic changes, through the organisation ofworkshops, where interdisciplinary research can be discussed, and throughpublications (e.g. Florindo et al., 2003, 2005, 2008; Barrett et al., 2006),allowing dissemination of results to a wide audience. It is only through suchintegration of geological data and numerical modelling that quantitativeassessments of past changes, and possible future scenarios, can be achieved.

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