Submarine landforms and the behavior of a surging ice cap since the last glacial maximum: The open-marine setting of eastern Austfonna, Svalbard

Robinson, P. H.; Dowdeswell, Julian A.

doi:10.1016/j.margeo.2011.06.004

Cited by 24 publications

(24 citation statements)

References 60 publications

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“…Basin-3 is known to have surged some time prior to 1870 (Lefauconnier and Hagen, 1991), and the advancing terminus created a pronounced surge lobe nearly 25 km in width. The terminal moraine associated with the last surge lies ∼ 8 km from the present-day position of the calving front (Robinson and Dowdeswell, 2011). Based on lobe volume and accumulation rate, the duration of the quiescent phase of Basin-3 was estimated to last 130-140 years (Solheim, 1991), a very good estimate considering the basin's renewed surge activity since autumn 2012, which is reported on here.…”

Section: Austfonna Basin-3supporting

confidence: 56%

Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt

et al. 2015

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Abstract. Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the polar regions. Here we present continuous GPS measurements and satellite synthetic-aperture-radar-based velocity maps from Basin-3, the largest drainage basin of the Austfonna ice cap, Svalbard. Our observations demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of Basin-3. The resulting iceberg discharge of 4.2 ± 1.6 Gt a −1 over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. With the seawater displacement by the terminus advance accounted for, the related sea-level rise contribution amounts to 7.2 ± 2.6 Gt a −1 . This rate matches the annual ice-mass loss from the entire Svalbard archipelago over the period [2003][2004][2005][2006][2007][2008], highlighting the importance of dynamic mass loss for glacier mass balance and sea-level rise. The active role of surface melt, i.e. external forcing, contrasts with previous views of glacier surges as purely internal dynamic instabilities. Given sustained climatic warming and rising significance of surface melt, we propose a potential impact of the hydro-thermodynamic feedback on the future stability of ice-sheet regions, namely at the presence of a cold-based marginal ice plug that restricts fast drainage of inland ice. The possibility of large-scale dynamic instabilities such as the partial disintegration of ice sheets is acknowledged but not quantified in global projections of sea-level rise.

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Section: Austfonna Basin-3supporting

confidence: 56%

Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt

et al. 2015

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“…Subsequently, the terminus retreated ∼8 km from its maximum extent marked by the position of a large submarine push moraine (Robinson and Dowdeswell, 2011). The observed surface profile is relatively flat (Dowdeswell, 1986).…”

Section: Basin-3mentioning

confidence: 94%

“…Several basins are known to have surged in the past; Etonbreen and Bråsvellbreen in the 1930s and Basin-3 around 1850-1870 (Schytt, 1969;Lefauconnier and Hagen, 1991). A submarine push-moraine in front of Basin-5, a northeastern neighbour of Basin-3, also suggests that this basin may have surged, probably within the past 100 years (Robinson and Dowdeswell, 2011). Currently observed elevation changes display interior thickening at rates of up to 0.5 m a −1 and marginal thinning at 1-3 m a −1 (Bamber et al, 2004;Moholdt et al, 2010) and can be explained by low ice flux rates within surge-type basins in their quiescent phase (Hagen et al, 2005;Bevan et al, 2007).…”

Section: The Austfonna Ice Capmentioning

confidence: 95%

Seasonal speed-up of two outlet glaciers of Austfonna, Svalbard, inferred from continuous GPS measurements

et al. 2012

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Abstract.A large part of the ice discharge from ice caps and ice sheets occurs through spatially limited flow units that may operate in a mode of steady flow or cyclic surge behaviour. Changes in the dynamics of distinct flow units play a key role in the mass balance of Austfonna, the largest ice cap on Svalbard. The recent net mass loss of Austfonna was dominated by calving from marine terminating outlet glaciers. Previous ice-surface velocity maps of the ice cap were derived by satellite radar interferometry (InSAR) and rely on data acquired in the mid-1990s with limited information concerning the temporal variability. Here, we present continuous Global Positioning System (GPS) observations along the central flowlines of two fast flowing outlet glaciers over [2008][2009][2010]. The data show prominent summer speedups with ice-surface velocities as high as 240 % of the presummer mean. Acceleration follows the onset of the summer melt period, indicating enhanced basal motion due to input of surface meltwater into the subglacial drainage system. In 2008, multiple velocity peaks coincide with successive melt periods. In 2009, the major melt was of higher amplitude than in 2008. Flow velocities appear unaffected by subsequent melt periods, suggesting a transition towards a hydraulically more efficient drainage system. The observed annual mean velocities of Duvebreen and Basin-3 exceed those from the mid-1990s by factors two and four, respectively, implying increased ice discharge at the calving front. Measured summer velocities up to 2 m d −1 for Basin-3 are close to those of Kronebreen, often referred to as the fastest glacier on Svalbard.

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“…, ; Streuff et al . ) as well as in Nordaustlandet (Solheim ; Robinson & Dowdeswell ; Flink et al . ; Fransner et al .…”

mentioning

confidence: 99%

“…1A) is, however, considerably less well known, mainly because these areas are covered by sea ice during large parts of the year and are logistically harder to access. A few studies have used marine geophysical methods to investigate Holocene glacier dynam-ics on the east coast of Spitsbergen (Noormets et al 2016a, b;Streuff et al 2017) as well as in Nordaustlandet (Solheim 1985;Robinson & Dowdeswell 2011;Flink et al 2017;Fransner et al 2017). None of the fjords or bays in central east Spitsbergen, such as Wiche-, Mohn-, Duner-or Agardhbukta has, however, been investigated with marine geophysical or sedimentological methods.…”

mentioning

confidence: 99%

Holocene glacial evolution of Mohnbukta in eastern Spitsbergen

Flink¹,

Hill²,

Noormets³

et al. 2017

Boreas

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Submarine geomorphology is one of the main tools for understanding past fluctuations of tidewater glaciers. In this study we investigate the glacial history of Mohnbukta, on the east coast of Spitsbergen, Svalbard, by combining multibeam‐bathymetric data, marine sediment cores and remote sensing data. Presently, three tidewater glaciers, Heuglinbreen, Königsbergbreen and Hayesbreen calve into Mohnbukta. Hayesbreen surged at the end of the Little Ice Age, between 1901 and 1910. The submarine landform assemblage in Mohnbukta contains two large transverse ridges, interpreted as terminal moraines, with debrisflow lobes on their distal slopes and sets of well‐preserved geometric networks of ridges, interpreted as crevasse‐squeeze ridges inshore of the moraines. The arrangement of crevasse‐squeeze ridges suggests that both landform sets were produced during surge‐type advances. The terminus position of the 1901–1910 Hayesbreen surge correlates with the inner (R.2) terminal moraine ridge suggesting that the R.1 ridge formed prior to 1901. Marine sediment cores display 14C ages between 5700–7700 cal. a BP derived from benthic foraminifera, from a clast‐rich mud unit. This unit represents pre‐surge unconsolidated Holocene sediments pushed in front of the glacier terminus and mixed up during the 1901 surge. An absence of retreat moraines in the deeper part of the inner basin and the observation of tabular icebergs calving off the glacier front during retreat suggest that the front of Hayesbreen was close to flotation, at least in the deeper parts of the basin. As the MOH15‐01 core does not penetrate into a subglacial till and the foraminifera in the samples were well preserved, the R.1 ridge is suggested to have formed prior to the deposition of the foraminifera. Based on these data we propose that a surge‐type advance occurred in Mohnbukta in the early Holocene, prior to 7700 cal. a BP, which in turn indicates that glaciers can switch to and from surge mode.

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Submarine landforms and the behavior of a surging ice cap since the last glacial maximum: The open-marine setting of eastern Austfonna, Svalbard

Cited by 24 publications

References 60 publications

Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt

Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt

Seasonal speed-up of two outlet glaciers of Austfonna, Svalbard, inferred from continuous GPS measurements

Holocene glacial evolution of Mohnbukta in eastern Spitsbergen

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