Elsevier

Quaternary Science Reviews

Volume 169, 1 August 2017, Pages 131-147
Quaternary Science Reviews

Retreat patterns and dynamics of the Sentralbankrenna glacial system, central Barents Sea

https://doi.org/10.1016/j.quascirev.2017.06.004Get rights and content

Abstract

The Barents Sea Ice Sheet (BSIS) is a good palaeo-analogue for the present day West Antarctic Ice Sheet. Both were marine-based ice sheets, particularly vulnerable to ocean warming and sea-level rise. Understanding the BSIS ice dynamics and patterns of retreat since the Last Glacial Maximum (LGM) is useful in developing our knowledge of spatial and temporal variations during marine-based ice sheet retreat. While the western margins of the Barents Sea have been extensively studied, few studies have focused on the central regions, which hosted key ice stream tributaries and major ice domes and divides. Presenting a new high-resolution (5 m) bathymetric dataset, this glacial geomorphological study focuses on the Sentralbankrenna palaeo-glacial system in the central Barents Sea. A large number of grounding zone wedges, mega-scale glacial lineations and areas with tunnel valleys and palaeo-subglacial basins were identified. These form the basis for a six-stage reconstruction of ice stream retreat through deglaciation since the LGM. In reconstructing the retreat of the Sentralbankrenna Ice Stream, we document the rapid but highly spatially variable pattern of retreat of a marine-based ice sheet margin. The presence of several tunnel valleys and interconnected palaeo-subglacial basin systems indicates an abundance of meltwater, likely to have been stored and released through several discharge events, significantly influencing the ice stream margin dynamics. This study provides insight into the behaviour and dynamics of ice during the late stages of the BSIS deglaciation within the central Barents Sea, increasing our understanding of grounding line processes.

Introduction

Ice streams are important and highly dynamic components of contemporary- and palaeo-ice sheets, transporting large amounts of ice and sediment from the ice sheet interior to the margins (Bamber et al., 2000); thereby significantly influencing the stability of the ice sheet (Bennett, 2003). Insight into the processes that occur at ice margins is of vital importance for understanding ice-ocean interactions and the consequences of ocean warming (Alley et al., 2005, Bindschadler, 2006, Pritchard et al., 2009). In particular, processes occurring at the grounding zones (where grounded ice loses contact with the bed), where a large amount of mass is lost by calving and melting (Jenkins and Doake, 1991, Rignot and Jacobs, 2002). This, in conjunction with other climatic changes, can lead to acceleration of ice streams, promoting destabilisation in the interior of the ice sheet (Oppenheimer, 1998, Rignot et al., 2004; Shepherd et al., 2004; Bindschadler, 2006). Present day Antarctic and Greenland Ice Sheets are vulnerable to oceanographic and climatic changes, such as increasing surface water temperatures and atmospheric warming, particularly at their ocean margins, thus it is essential to develop our understanding of the processes and mechanisms that influence the spatial and temporal retreat of ice streams.

During the Last Glacial Maximum (LGM; 18–21 cal ka BP) a large marine-based ice sheet covered the Barents Sea, extending to the western continental shelf break (Fig. 1; Svendsen et al., 2004). The Barents Sea Ice Sheet (BSIS) is considered a good palaeo-analogue for marine-based ice sheets (Siegert et al., 2002) such as the present-day West Antarctic Ice Sheet (WAIS). They have many similarities, both are marine-based with their beds mostly below sea-level, both are overlying sedimentary bedrock, and had similar sizes and extents during the LGM (Andreassen and Winsborrow, 2009). However, unlike the WAIS, the BSIS completely deglaciated following the LGM.

Details of its deglaciation history are preserved in the glacial sediments and landforms imprinted onto the seafloor of the Barents Sea and have been extensively studied in southwest Barents Sea and parts of the Svalbard margin (Fig. 1; i.e. Vorren and Kristoffersen, 1986, Elverhøi et al., 1993, Solheim et al., 1996, Landvik et al., 1998, Dowdeswell et al., 2010, Winsborrow et al., 2010, Rüther et al., 2012, Ingólfsson and Landvik, 2013, Andreassen et al., 2014, Bjarnadóttir et al., 2014, Piasecka et al., 2016). In contrast, the central Barents Sea remains poorly studied, despite it being the site of a major ice dome and ice divides for the BSIS, as well as hosting several ice streams and their tributaries.

Ice streams leave a series of characteristic geomorphic imprints on the seafloor, which document the spatial and temporal patterns of retreat. By studying these we can gain valuable insights into the processes and mechanisms controlling ice stream behaviour (Stokes and Clark, 2001, Livingstone et al., 2012a).

Until recently, there has been a particular scarcity of bathymetric data available from the central Barents Sea due to a political Norwegian-Russian border dispute. This is in contrast to that available from the southwestern Barents Sea where several surveys have been undertaken. We present a high-resolution dataset from the central Barents Sea, immediately west of the border between Norway and Russia (Fig. 1). Focusing on the Sentralbankrenna Ice Stream and its glacial system, which encompasses the adjacent bank areas Sentralbanken and Thor Iversenbanken. The Sentralbankrenna Ice Stream was a tributary to Bjørnøyrenna during the LGM and an important area during the final stages of the central BSIS deglaciation. In this paper, we present glacial geomorphological mapping from the bed of the Sentralbankrenna palaeo-Ice Stream, which is then interpreted to determine ice flow patterns and ice dynamics during deglaciation. We document rapid, episodic ice stream retreat associated with periods of increased ice margin break up punctuated by margin stillstands or short readvances. Subglacial meltwater was abundant in this area and is suggested to have significantly influenced the overlying ice by facilitating fast flow both for the Sentralbankrenna and Bjørnøyrenna Ice Stream.

Section snippets

Glacial and regional setting/Study area

The Barents Sea is the largest epi-continental sea in the world and is characterised by relatively shallow banks (100–200 mbsl) and large, deep troughs (300–500 mbsl; Fig. 1). Investigations into the large trough mouth fans at the shelf break suggest that the Barents Sea has undergone multiple glaciations during the Cenozoic (Vorren et al., 1988, Vorren and Laberg, 1997), with the most recent having taken place in the Late Weichselian (Landvik et al., 1998, Svendsen et al., 2004). During this

Datasets and method

The bathymetric data presented herein was provided by the MAREANO Programme (www.mareano.no). The original dataset has a horizontal resolution of 5 m, with the multibeam covering an area of approximately ∼17,000 km2 over Sentralbankrenna and the northwestern flanks of Thor Iversenbanken (Fig. 1). The horizontal grid size was decreased during the mapping stage to a resolution of 25 m to focus on the larger-scale glacial features. The bathymetric dataset was used to carry out detailed mapping of

Results and interpretation

The key glacial landforms identified in the study area are described and interpreted below (Fig. 2A). The results are then synthesised (Fig. 2B and E), providing new insights into the spatial and temporal variations of the ice margin and the distribution of fast and slow flowing ice within the Sentralbankrenna glacial system during the final stages of BSIS deglaciation, as well as the influence of this glacial system on the wider BSIS.

The Sentralbankrenna glacial system

A complex assemblage of glacial landforms was mapped in the study area, composing of multiple grounding zone deposits, MSGLs, meltwater features and retreat ridges. Based on this geomorphological record we propose that the Sentralbankrenna glacial system experienced several retreats and/or readvances, each marked by a GZW or GZD, during the period of overall deglaciation since the LGM. The glacial system comprised of the fast flowing Sentralbankrenna Ice Stream and slower moving inter-ice

Conclusions

Unlike the western Barents Sea which has been extensively investigated, the central Barents Sea remains scarcely studied. Observations and insights gained in this study have contributed to the overall knowledge of the BSIS deglaciation, particularly during the later stages. Analysis of a new high resolution bathymetric dataset, presented in this study, revealed glacial landform assemblages related to both the former Sentralbankrenna Ice Stream and the inter-ice stream areas in the adjacent

Acknowledgements

We would like to acknowledge Kartverket (the Norwegian Hydrographic Service), the Geological Survey of Norway and the MAREANO programme for the provision of this dataset, used here under a CC by 4.0 license (https://creativecommons.org/licenses/by/4.0/legalcode). This is a contribution to CAGE (Centre for Arctic Gas Hydrate, Environment and Climate) that is funded by the Research Council of Norway through the Centre of Excellence funding scheme grant no. 223259. Furthermore, we would like to

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