scholarly journals Mechanical effect of mélange-induced buttressing on embayment-terminating glacier dynamics

2012 ◽  
Vol 6 (5) ◽  
pp. 4123-4136 ◽  
Author(s):  
D. Seneca Lindsey ◽  
T. K. Dupont
Keyword(s):  
Boundary Condition ◽  
Sea Ice ◽  
Mass Loss ◽  
Mechanical Effect ◽  
Front Velocity ◽  
Kinematic Boundary Condition ◽  
Glacier Dynamics ◽  
Front Advance ◽  
Calving Rate ◽  
The 1950S

Abstract. Embayment terminating glaciers interact dynamically with seasonal sea ice and icebergs, a mixture we refer to as mélange. For certain glaciers, mélange prevents calved bergs from rotating away from the front, thus allowing the ice front to advance into the embayment. Here we demonstrate that mélange can, if rigid enough, provide sufficient buttressing to reduce the calving rate, while leaving the ice-front velocity largely unaffected. The net result is additional ice-front advance. Observations indicate a seasonal advance/retreat cycle has occurred at Jakobshavn Isbræ since the 1950s. We model an idealized Jakobshavn Isbræ-like scenario and find that mélange may be responsible for a seasonal ice-front advance of up to 0.6 km. These results come from a model that incorporates mélange into the interior of the domain, includes relevant stresses, and models drag via a kinematic boundary condition. A weakening or loss of mélange due to increasing temperatures would lead to further mass loss from glaciers such as Jakobshavn Isbræ.

Application of Satellite Remote Sensing Techniques to Quantify Terminus and Ice Mélange Behavior at Helheim Glacier, East Greenland

2014 ◽  
Vol 48 (5) ◽  
pp. 81-91 ◽  
Author(s):  
Steve Foga ◽  
Leigh A. Stearns ◽  
C.J. van der Veen
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
East Greenland ◽  
Object Based Image Analysis ◽  
Glacier Terminus ◽  
Object Based ◽  
Radar Imagery ◽  
Iceberg Calving ◽  
Calving Rate ◽  
Remote Sensing Techniques

AbstractIceberg calving is an efficient mechanism for ice mass loss, and rapidly calving glaciers are often considered to be inherently unstable. However, the physical controls on calving are not well understood. Recent studies hypothesize that the presence of a rigid ice mélange (composed of icebergs, bergy bits, and sea ice) can reduce iceberg calving by providing “backstress” to the terminus. To test this hypothesis we use remote sensing techniques to construct a time series model of calving rate and size and composition of the adjacent ice mélange. We describe a semi-automated routine for expediting the digitization process and illustrate the methods for Helheim Glacier, East Greenland, using 2008 data. Ice velocities of the glacier terminus and ice mélange are derived with feature-tracking software applied to radar imagery, which is successfully tracked year-round. Object-based image analysis (OBIA) is used to inventory icebergs and sea ice within the ice mélange. We find that the model successfully identifies the calving rate and ice mélange response trends associated with seasonal increases in terminus retreat and advance and shows seasonal trends of ice mélange potentially providing seasonal backstress on the glacier terminus.

scholarly journals 21st century estimates of mass loss rates from glaciers in the Gulf of Alaska and Canadian Archipelago using a GRACE constrained glacier model

2020 ◽  
Author(s):  
Lavanya Ashokkumar ◽  
Christopher Harig
Keyword(s):  
Mass Loss ◽  
21St Century ◽  
Gulf Of Alaska ◽  
Baffin Island ◽  
Emission Scenarios ◽  
Glacier Dynamics ◽  
Constrained Models ◽  
Atmospheric Changes ◽  
Specific Scenario ◽  
Loss Rates

Abstract. Ice mass loss rates from glaciers in the Gulf of Alaska and the Canadian Archipelago are expected to increase through the end of century in response to increasing temperatures. Here, we develop a new glacier model constrained by GRACE gravimetry observations for the period between 2002 and 2017. The high temporal and regional spatial resolution of GRACE mass balance estimates allows us to estimate regional glacier sensitivities to atmospheric changes, and account for higher order of glacier dynamics. We use our regionally constrained models to extrapolate future mass loss under different climate emission scenarios. Generally our 21st century sea level estimates are at the high end compared to other studies. We find that the Gulf of Alaska exhibits the highest mass loss rates between −79 to −112 Gt yr−1 between 2006 and 2100 under different scenarios, and displays the highest sensitivity to the specific scenario (RCP 2.6/4.5/8.5). Our estimates for Baffin Island are significantly higher than prior work (−57 to −85 Gt yr−1) and are comparable to projected mass loss rates from the Ellesmere region (−63 to −101 Gt yr−1).

scholarly journals Glacier dynamics over the last quarter of a century at Jakobshavn Isbræ

2015 ◽  
Vol 9 (5) ◽  
pp. 4865-4892
Author(s):  
I. S. Muresan ◽  
S. A. Khan ◽  
A. Aschwanden ◽  
C. Khroulev ◽  
T. Van Dam ◽  
...  
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
21St Century ◽  
Greenland Ice Sheet ◽  
Outlet Glacier ◽  
The Past ◽  
Glacier Dynamics ◽  
The Future ◽  
Oceanic Forcing

Abstract. Observations over the past two decades show substantial ice loss associated with the speedup of marine terminating glaciers in Greenland. Here we use a regional 3-D outlet glacier model to simulate the behaviour of Jakobshavn Isbræ (JI) located in west Greenland. Using atmospheric and oceanic forcing we tune our model to reproduce the observed frontal changes of JI during 1990–2014. We identify two major accelerations. The first occurs in 1998, and is triggered by moderate thinning prior to 1998. The second acceleration, which starts in 2003 and peaks in summer 2004, is triggered by the final breakup of the floating tongue, which generates a reduction in buttressing at the JI terminus. This results in further thinning, and as the slope steepens inland, sustained high velocities have been observed at JI over the last decade. As opposed to other regions on the Greenland Ice Sheet (GrIS), where dynamically induced mass loss has slowed down over recent years, both modelled and observed results for JI suggest a continuation of the acceleration in mass loss. Further, we find that our model is not able to capture the 2012 peak in the observed velocities. Our analysis suggests that the 2012 acceleration of JI is likely the result of an exceptionally long melt season dominated by extreme melt events. Considering that such extreme surface melt events are expected to intensify in the future, our findings suggest that the 21st century projections of the GrIS mass loss and the future sea level rise may be larger than predicted by existing modelling results.

scholarly journals Atlantic Water advection vs glacier dynamics in northern Spitsbergen since early deglaciation

2017 ◽  
Author(s):  
Martin Bartels ◽  
Jürgen Titschack ◽  
Kirsten Fahl ◽  
Rüdiger Stein ◽  
Marit-Solveig Seidenkrantz ◽  
...  
Keyword(s):  
Sea Ice ◽  
Environmental Conditions ◽  
Late Holocene ◽  
Ice Cover ◽  
Atlantic Water ◽  
Sea Surface ◽  
Early Holocene ◽  
Sea Surface Temperatures ◽  
Surface Temperatures ◽  
Glacier Dynamics

Abstract. Atlantic Water (AW) advection plays an important role for climatic, oceanographic and environmental conditions in the eastern Arctic. Situated along the only deep connection between the Atlantic and the Arctic Ocean, the Svalbard Archipelago is an ideal location to reconstruct the past AW advection history and document its linkage with local glacier dynamics, as illustrated in the present study of a sedimentary record from Woodfjorden (northern Spitsbergen) spanning the last ~ 15 500 years. Sedimentological, micropalaeontological and geochemical analyses were used to reconstruct changes in marine environmental conditions, sea-ice cover and glacier activity. Data illustrate a partial breakup of the Svalbard–Barents–Sea Ice Sheet from Heinrich Stadial 1 onwards (until ~ 14.6 ka BP). During the Bølling-Allerød (~ 14.6–12.7 ka BP), AW penetrated as a bottom water mass into the fjord system and contributed significantly to the destabilisation of local glaciers. During the Younger Dryas (~ 12.7–11.7 ka BP), it intruded into intermediate waters while evidence for a glacier advance is lacking. A short-term deepening of the halocline occurred at the very end of this interval. During the early Holocene (~ 11.7–7.8 ka BP), mild conditions led to glacier retreat, a reduced sea-ice cover and increasing sea surface temperatures, with a brief interruption during the Preboreal Oscillation (~ 11.1–10.8 ka BP). During the late Holocene (~ 1.8–0.4 ka BP), a slightly reduced AW inflow and lower sea surface temperatures compared to the early Holocene are reconstructed. Glaciers, which previously retreated to the shallower inner parts of the Woodfjorden system, likely advanced during the late Holocene. In particular, as topographic control in concert with the reduced summer insolation partly decoupled glacier dynamics from AW advection during this recent interval.

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