Interaction between subsurface ocean waters and calving of the Jakobshavn Isbræ during the late Holocene

Abstract

'Interaction between subsurface ocean waters and calving of Jakobshavn Isbrae during the Late Holocene.', The Holocene., 21 (2). pp. 211-224. Further information on publisher's website:http://dx.doi.org/10.1177/0959683610378877Publisher's copyright statement:The nal denitive version of this article has been published in the Journal 'The Holocene' 21/2, 2011 c The Authors by SAGE Publications Ltd at the The Holocene page: http://hol.sagepub.com on SAGE Journals Online: http://online.sagepub.com/ Additional information: 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-prot 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. A. IntroductionIt is becoming increasingly clear that the cryosphere is responding quickly to the atmospheric temperature increase observed over recent decades (Box et al., 2006;Fettweis, 2007; Hanna et al. 2 2008;Mernild et al. 2008a). However, prediction of the contribution of the Greenland ice sheet to global sea-level rise is complicated by the lack of detailed knowledge on mechanisms behind ice sheet change. In particular ice streams and their interaction with the atmospheric and oceanic systems needs further investigation in order to make more realistic models of future sea-level rise.In this study the Late Holocene climate history of the Jakobshavn Isbrae region ( also been proposed as a crucial mechanism triggering ice sheet destabilisation and large-scale iceberg surges during glacial periods (Moros et al., 2002). Following these observations we aim at evaluating if intrusion of relatively warmer waters into Disko Bugt occurred on multi-decadal to centennial timescales and if so how these incursions affected the calving of icebergs. This may shed light on whether the modern acceleration of the Jakobshavn Isbrae is one of a kind and whether ocean-ice-sheet interaction is an important component of the climate-cryosphere system that needs to be assessed in details in climate models.Variability of the subsurface and surface water is reconstructed by analysis of the benthic foraminiferal and dinoflagellate assemblage, respectively, and the production of icebergs and sea-ice is reconstructed on the basis of the ice-rafted debris in the sediment core. produced by, among others, the Jacobshavn Isbrae.The modern day climate of the Disko Bugt region is low arctic maritime with a mean annual temperature of -5.2°C, a summer mean of 4.8°C (Fredskild, 1996) and high precipitation.The bay is typically covered by land-fast sea-ice from mid-January to mid-April with a mean thickness of 0.7 m (Buch, 2000). During spring and summer a strong pycnocline is developed ...

Oceanographic regime shift during 1997 in Disko Bay, Western Greenland

“…The questions that remain are: how long will these warmer oceanographic conditions along the Greenlandic coast prevail, and what will be the subsequent effect of a greater input of freshwater from ice melt? Altered circulation patterns have implications for the hydrography of Greenlandic fjords and the subsequent melting of deep bed glaciers, as seen during the last 10,000 yr (Andresen et al 2011), and one can also expect considerable ecological effects in these productive coastal waters. Changes in key species at the base of marine food web will have implications for Greenlandic society (cultural hunting) and industry (fisheries and tourism).…”

“…Recently, a series of studies have documented the effects that warm Atlantic waters (AW) in Greenlandic fjords have on increasing submarine glacial melting and the subsequent acceleration of past (Andresen et al 2011) and recent glacial retreat (Holland et al 2008;Rignot et al 2010;Lloyd et al 2011). These warm waters originate from the Irminger Current.…”

Multidecadal to millennial marine climate oscillations across the Denmark Strait (~ 66° N) over the last 2000 cal yr BP

“…2) -the IC is a surface current off SW Iceland, a surface or intermediate current off N Iceland, and an intermediate water mass in the deep troughs and fjords of E and SE Greenland -variations in the latter are a prime cause for changes in the tidewater glacier dynamics of the area (Syvitski et al, 1996;Andresen et al, 2011). A number of Arctic/North Atlantic climate reconstructions have been developed, including a 2000 yr estimate of Arctic summer temperatures (Kaufman et al, 2009) (Fig.…”

Northward advection of Atlantic water in the eastern Nordic Seas over the last 3000 yr

“…The manifestation of the late Holocene (last ∼ 3000 yr) trend toward positive NAO conditions can be inferred from various marine proxy records around Greenland showing colder conditions associated with decreased AW influence in Discobay (western Greenland) related to the so-called "seesaw" pattern (Seidenkrantz et al, 2008;Andresen et al, 2011Andresen et al, , 2012, and an increased flux of sea ice/icebergs east of Greenland (Jennings et al, 2002). Accordingly, Moros et al (2004) interpreted the patterns of increased abundance of ice-rafted detritus (IRD) in the western parts of the Nordic Seas (Jennings et al, 2002) and decreased IRD in the Norwegian Sea (their work) to a strengthening of both the NAC and the EGC from the mid-Holocene to present.…”

“…Compared with the preceding early to mid-Holocene climate optimum, the neoglaciation has been widely recorded in both terrestrial and marine archives in the North Atlantic region (Jennings et al, 2002;Seidenkrantz et al, 2008;Kaufman et al, 2009, and references herein; Andresen et al, 2011;Müller et al, 2012) as a time of expansion of Scandinavian glaciers (Nesje et al, 1991(Nesje et al, , 2001, increased sea ice cover and colder surface waters in the Barents Sea and part of Fram Strait (Duplessy et al, 2001;Risebrobakken et al, 2010;Kinnard et al, 2011;Müller et al, 2012), colder surface and subsurface waters off western Norway (Calvo et al, 2002;Moros et al, 2004;Hald et al, 2007;Sejrup et al, 2011) and overall colder conditions over northern Europe (Bjune et al, 2009). This cooling trend was punctuated by several warm and cold spells such as the Roman Warm Period and Medieval Climate Anomaly (RWP, MCA), and the Little Ice Age (LIA).…”