Published 26.08.2009. Written by Endre Før Gjermundsen.

Icebound – enclosed in ice

Reconstruction of the last glacial Svalbard-Barents sea ice sheet.


Relevance

The relevance of the icebound project is two-folded:

1. A better knowledge of the last glacial ice sheet has important implications for models studying hydrocarbon migration. Developing useful data about the last ice sheet load and its geometry on Svalbard is essential for constraining framework conditions of pressure development in the Svalbard Barents Sea.

2. Svalbard is a key region for understanding the interaction of ice and the thermohaline circulation (THC). Ocean-climate models suggest that rapid freshwater releases with the deglaciation of Northern hemisphere ice sheets are associated with fluctuations in the thermohaline ocean circulation. Earth system models will profit from data that constrain the volume of the last ice sheet and its deglaciation in order to predict future changes of the ocean circulation.

Background

1. Since the first publication concerning the influence of glacial erosion and isostasy on hydrocabon bearing rocks in the Barents Sea (Kjemperud and Fjeldskaar, 1992) a considerable improvement in our understanding of the former Svalbard-Barents sea ice sheet has been established. Our present understanding of the last ice sheet is far more complex than a simple ice sheet with one ice dome having a thickness of 400-1200 m (Siegert and Dowdeswell, 2004). Based on geophysical measurements it is assumed that highly dynamic ice streams covered the fjord systems while many parts inland were covered by less dynamic cold based ice shown by terrestrial studies (Landvik et al., 2005; Andreassen et al., 2007; Dowdeswell et al., 2007; Ottesen et al., 2007; Andreassen et al., 2008; Ottesen and Dowdeswell, 2009). In a modelling investigation it has been suggested that the ice sheet loading effects the reservoir pressure and temperature on hydrocarbon phase separation and migration. Glacial erosion and changes in the thickness of the ice sheet coverage results in thermal disequilibrium and renewed hydrocarbon migration (Cavanagh et al., 2005; Cavanagh et al., 2006). The authors propose that during initial stages of interglacial conditions hydrocarbon gas reservoirs might experience leakage. A better reconstruction of glacial, interglacial and interstadial timing is a new avenue for a improved understanding of late hydrocarbon migration and present day leakage in the Barents Sea as boundary condition for hydrocarbon reservoir migration models.

2. Earth system models looking into feedback processes with the thermohaline ocean circulation provide clear indications that ice sheet-ocean interactions, ice melt and subsequent freshwater flux to the Nordic Seas and the Arctic Ocean play an important role in triggering shifts in the ocean circulation (Schmittner and Clement, 2002; Siegert and Dowdeswell, 2004; Death et al., 2006). Although significant uncertainties exist regarding the volume and timing of former ice sheets in many areas. The timing and volume of freshwater discharge into the Arctic Ocean from the Svalbard-Barents sea ice has never been quantified. Accurate quantification of past freshwater flux, and their timing relative to climate changes, is essential for calibrating earth system models, and improving their predictive power.

Status of knowledge

Major research efforts during the ESF-funded QUEEN project (Quaternary environment of the Eurasian North - until mid-2003) lead to the hypothesis that fast-flowing ice streams covered the fjord troughs flowing to the shelf edge (Siegert et al., 2001; Siegert and Dowdeswell, 2004; Allen et al., 2007). Main evidence comes from high-resolution seismics, bathymetry data and marine sediment studies (Elverhøi et al., 1995; Svendsen et al., 1996; Ottesen et al., 2005; Ottesen et al., 2007; Andreassen et al., 2008). In addition we have well documented evidence from terrestrial geological data sets of post-glacial isostatic uplift measured across high Arctic archipelagos (Forman, 1990; Forman et al., 1999; Forman et al., 2004; Svendsen et al., 2004).

In some regions between deeper fjord systems terrestrial evidence has been presented indicating ice-free regions or regions that were potentially covered with thin cold based glacier ice (Blake, 1962; Lehman and Forman, 1992; Landvik et al., 2005). With the rather new method of cosmogenic nuclide dating (CN) using two different cosmogenic nuclides 10Be, 26Al it is possible to investigate if bedrock surfaces were covered by cold based glacier ice or ice-free during the late Weichselian (Fabel et al., 2002; Briner et al., 2003; Briner et al., 2005; Briner et al., 2006; Ivy-Ochs and Kober, 2008). The CN method has been used previously in one research project on Svalbard supporting ice-free areas in the NW of the archipelago (Landvik et al., 2003). Within that study, the constraints on the dating method itself were not investigated.

There is geological data indicating that larger glaciations must have been significantly older than late Weichselian and large late Weichselian ice sheets had existed neither in northern Siberia nor in Beringia (Brigham-Grette, 2001; Svendsen et al., 2002). In the Arctic Ocean only limited IRD (ice rafted debris) is observed in comparison to earlier glaciations (Spielhagen et al., 2004). Preliminary CN results from a prequel study in Nordaustlandet indicates that the late Weichselian glaciation was restricted in comparison to the mid-Weichselian glaciation (Hormes et al., 2008; Hormes et al., to be submitted). The late Weichselian glaciation was constrained to the fjord geomorphology flowing along present fjord troughs, while the mid-Weichselian glaciation covered higher landscapes and the ice flow regime was detached from the fjords (Kaakinen et al., 2009; Hormes et al., to be submitted).

Therefore, there is still a lack of knowledge about the extension and thickness of the late Weichselian ice sheet on Svalbard in contrast to older glaciations.

The proposed project will combine new glacial geological evidence and CN dating to determine former ice sheet geometry in Svalbard, to provide a firm foundation as boundary conditions for hydrocarbon migration models in the Barents Sea and Earth system models to test their performance during last deglaciation.

Objectives

The project will allow for more accurate former ice sheet geometry on Svalbard which will in turn provide more accurate boundary conditions for hydrocarbon migration models. We want to combine the following approaches in order to deliver some new terrestrial data of the ice sheet development in the Svalbard region.

  • Mapping glacial trimlines in selected mountain areas
  • Dating trimlines by means of cosmogenic nuclides (CN) in order to constrain the vertical dimensions of the last ice sheet inland
  • CN dating and bedrock source analysis of erratic boulders in order to constrain the age of deglaciation and ice flow directions during the late Weichselian

Project posters

References

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