Antarctica is a continent locked in ice, with almost 99.7% of current terrain covered by permanent ice and snow, and clear evidence that, as recently as the Last Glacial Maximum (LGM), ice sheets were both thicker and much more extensive than they are now. Ice sheet modelling of both the LGM and estimated previous ice maxima across the continent give broad support to the concept that most if not all currently ice-free ground would have been overridden during previous glaciations. This has given rise to a widely held perception that all Mesozoic (pre-glacial) terrestrial life of Antarctica was wiped out by successive and deepening glacial events. The implicit conclusion of such destruction is that most, possibly all, contemporary terrestrial life has colonised the continent during subsequent periods of glacial retreat. However, several recently emerged and complementary strands of biological and geological research cannot be reconciled comfortably with the current reconstruction of Antarctic glacial history, and therefore provide a fundamental challenge to the existing paradigms. Here, we summarise and synthesise evidence across these lines of research. The emerging fundamental insights corroborate substantial elements of the contemporary Antarctic terrestrial biota being continuously isolated in situ on a multi-million year, even pre-Gondwana break-up timescale. This new and complex terrestrial Antarctic biogeography parallels recent work suggesting greater regionalisation and evolutionary isolation than previously suspected in the circum-Antarctic marine fauna. These findings both require the adoption of a new biological paradigm within Antarctica and challenge current understanding of Antarctic glacial history. This has major implications for our understanding of the key role of Antarctica in the Earth System.

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Citation for published item: t miesonD F F F nd ieliD eF nd vivingstoneD FtF nd ¡ y gof ighD gF nd tokesD gF F nd rillen r ndD gEhF nd howdeswellD tFeF @PHIPA 9s eEstre m st ility on reverse ed slopeF9D x ture geos ien eFD S @IIAF ppF UWWEVHPF Further information on publisher's website: httpXGGdxFdoiForgGIHFIHQVGngeoITHH Publisher's copyright statement:Additional information:Read Durham University's press release about this article, available at:http://www.dur.ac.uk/news/newsitem/?itemno=15572 Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Ice streams are fast-flowing arteries of ice sheets that dominate ice discharge into the oceans, impacting directly upon sea level. Many ice streams possess beds that are below sea level and typically deepen inland on a reverse-slope 9 . Theory suggests that ice discharge increases rapidly with water depth 3 , and in the absence of lateral-drag induced buttressing from a floating ice shelf, grounding lines (marking the transition from grounded to floating ice) on reverse-bed slopes may be unstable 1-2 . Bed topography is therefore cited as a strong control on ice-stream retreat rate 3,10 and modern satellite observations of rapid ice-stream thinning and recession appear consistent with this theory 4-6 . However, with just two decades of data, these records are too short to identify the longerterm centennial to millennial-scale trends crucial for constraining future sea-level projections.Major uncertainties in predictions of ice-sheet vulnerability 11 relate to limitations in understanding processes controlling grounding-line motion and, importantly, to deficiencies in grounding-line treatment in ice-sheet models 12 . In recent years, significant advances in model development have been made 3,12-17 , but tests have only been applied to simplified bed geometries or to steady-state conditions and lack validation against data over timescales longer than a few decades. We aim to understand the long-term controls and stability of marine ice streams and, for the first time, 'pinning points' (e.g. at 500 km; Fig. 2). However, in the reverse-sloping portion of the bed and, significantly, in the absence of topographic highs, several slow-downs also occur. Moreover, the simulated stabilisations are broadly consistent with previously mapped GZW positions (Fig. 2).These short-term changes in retreat-rate occur adjacent to GZWs 1, 2, 3, 6, 7 and 8 and prolonged grounding-line stability is modelled between GZWs 4 and 5 where the reverse slope steepens into the overdeepened portion of Marguerite Trough...

The Antarctic Peninsula is one of the three fastest warming regions on Earth. Here we review Holocene proxy records of marine and terrestrial palaeoclimate in the region, and discuss possible forcing mechanisms underlying past change, with a specific focus on past warm periods. Our aim is to critically evaluate the mechanisms by which palaeoclimate changes might have occurred, in order to provide a longer-term context for assessing the drivers of recent warming. Two warm events are well recorded in the Holocene palaeoclimate record, namely the early Holocene warm period, and the `Mid Holocene Hypsithermal' (MHH), whereas there are fewer proxy data for the `Mediaeval Warm Period' (MWP) and the `Recent Rapid Regional' (RRR) warming. We show that the early Holocene warm period and MHH might be explained by relatively abrupt shifts in position of the Southern Westerlies, superimposed on slower solar insolation changes. A key finding of our synthesis is that the marine and terrestrial records in the AP appear to show markedly different behaviour during the MHH. This might be partly explained by contrasts in the seasonal insolation forcing between these records. Circumpolar Deep Water (CDW) has been implicated in several of the prominent changes through the Holocene but there are still differences in interpretation of the proxy record that make its influence difficult to assess. Further work is required to investigate contrasts between marine and terrestrial proxy records, east—west contrasts in palaeoclimate, the history of CDW, to retrieve a long onshore high resolution record of the Holocene, and determine the role of sea ice in driving or modulating palaeoclimate change, along with further efforts to study the proxy record of the RRR and the MWP.