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Multiple Late Holocene surges of a High-Arctic tidewater glacier system in Svalbard

Lovell, Harold and Benn, Douglas and Lukas, Sven and Ottesen, Dag and Luckman, Adrian and Hardiman, Mark and Barr, Iestyn and Boston, Clare and Sevestre, Heidi (2018) Multiple Late Holocene surges of a High-Arctic tidewater glacier system in Svalbard. Quaternary Science Reviews, 201. pp. 162-185. ISSN 0277-3791

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Abstract

Most large tidewater glaciers in Svalbard are known to have surged at least once in the last few hundredyears. However, very little information exists on the frequency, timing or magnitude of surges prior to theLittle Ice Age (LIA) maximum in ~1900. We investigate the sediment-landform assemblages produced bymultiple advances of the Nathorstbreen glacier system (NGS) in order to reconstruct its Late Holocenesurge history. The glacier has recently undergone one of the largest surges ever observed in Svalbard,advancing ~16 km from 2008 to 2016. We present flow velocities and ice-marginal observations (ter-minus change, proglacial geomorphological processes) from the later stages of this surge. A first detailedassessment of the development of a glaciotectonic mud apron within the fjord during a surge is provided.Geomorphological and sedimentological examination of the terrestrial moraine areas for med prior to themost recent surge reveals that at least two advances were responsible for their formation, based on theidentification of a previously unrecognised ice-contact zone recorded by the distribution of sedimentfacies in coastal exposures. We distinguish between an outer, older advance to the distal part of themoraine system and an inner, younger advance to a position ~2 km upfjord. Radiocarbon dating of shellsembedded in glaciotectonic composite ridges formed by the onshore bulldozing of marine mud duringthe outer (older) of the two advances shows that it occurred at some point during the interval 700e890 cal. yr BP (i.e. ~1160 AD), and not during the LIA as previously assumed. We instead attribute theinner (younger) advance to the LIA at ~1890. By combining these data with previous marine geologicalinvestigations in inner and outer Van Keulenfjorden, we demonstrate that NGS has advanced at least fourtimes prior to the recent 2008e2016 surge: twice at ~2.7 kyr BP, at ~1160 AD, and in ~1890. This rep-resents a unique record of the timing and magnitude of Late Holocene tidewater glacier surges inSvalbard

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