Large subglacial meltwater features in the central Barents Sea

L.R Bjarnadóttir,K Andreassen,M.C.M Winsborrow

doi:10.1130/g38195.1

L.R Bjarnadóttir, K Andreassen + Show 1 more

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https://doi.org/10.1130/g38195.1

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Abstract

During the last glacial period large parts of the Arctic, including the Barents Sea, north of Norway and Russia, were covered by ice sheets. Despite several studies indicating that melting occurred beneath much of the Barents Sea ice sheet, very few meltwater-related landforms have been identified. We document ∼200 seafloor valleys in the central Barents Sea and interpret them to be tunnel valleys formed by meltwater erosion beneath an ice sheet. This is the first account of widespread networks of tunnel valleys in the Barents Sea, and confirms previous predictions that large parts of the ice sheet were warm based. The tunnel valleys are interpreted to be formed through a combination of steady-state drainage and outburst floods close to the ice margin, as a result of increased melting within a period of rapid climate warming during late deglaciation. This is the first study documenting widespread tunnel valley formation at the northern reaches of a Northern Hemisphere paleo–ice sheet, during advanced deglaciation and beneath a much reduced ice sheet. This indicates that suitable conditions for tunnel valley formation may have occurred more widely than previously reported, and emphasizes the need to properly incorporate hydrological processes in current efforts to model ice sheet response to climate warming. This study provides valuable empirical data, to which modeling results can be compared.

Highlights

Over the past 2.6 m.y., the Barents Sea has undergone repeated shelf-wide glaciations, most recently during the late Weichselian, ca. 20 ka, during which the central part of the Barents Sea ice sheet remained marine based (Svendsen et al, 2004a)
Reconstructions of the late Weichselian Barents Sea ice sheet include a number of fast-flowing ice streams, indicating that lubricating meltwater was generated across large parts of the ice sheet base (e.g., Andreassen et al, 2008; Winsborrow et al, 2010; Bjarnadóttir et al, 2014)
We suggest that these tunnel valleys (TVs) were active, and likely formed close to ice margins during the last deglaciation of the Barents Sea

Summary

INTRODUCTION

Over the past 2.6 m.y., the Barents Sea has undergone repeated shelf-wide glaciations, most recently during the late Weichselian, ca. 20 ka, during which the central part of the Barents Sea ice sheet remained marine based (grounded below sea level) (Svendsen et al, 2004a). 17 ka (Rüther et al, 2011); the central Barents Sea was deglaciated between 16 and 14 ka (Fig. 1; Gataullin et al, 2001; Svendsen et al, 2004a, 2004b; Winsborrow et al, 2010; Andreassen et al, 2014; Bjarnadóttir et al, 2014; Hughes et al, 2016). This study documents ~200 hitherto unknown meltwater features (tunnel valleys and eskers) in the central Barents Sea (Fig. 1), confirming, for the first time, that there was widespread channelized meltwater drainage beneath the Barents Sea ice sheet. The resolution of the Olex data (vertical ~0.1–1 m, horizontal ~5–50 m) (Items DR1 and DR2 in the GSA Data Repository1) allows for mapping of large geomorphic seafloor features (>100 m wide and >10 m deep). Murmansk bank line: Kurentsovo line: Admiralty bank line: Ca. cal ka (ca.13 14C ka in Svendsen et al, 2004b & Gataullin et al, 2001)

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CONCLUSIONS