Marine glaciers, ice shelves & calving

What controls the grounding-line stabilisation?
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Terms in this set (18)
What controls the grounding-line stabilisation?
Bed topography, width of ice streams and the rate of the delivery of inland ice
What causes the break up of the Larsen B ice shelf
Self stimulating chain reaction drainage of the supraglacial lakes which caused the fracture system and the explosive break up
Glacier response to the disintegration of the larsen B i e shelf
Glacier speed up due to changes in stress perturbation and loss of buttressing effect. Another forcing is surface melting due to warming.
Why is the understanding of ice stream stability limited?
Observational records are too short for multi decadal and millennial scale behaviour and validation of numerical modles
What caused the synchronized drainage of the supraglacial meltwater lakes on the Larsen B Ice Shelf prior to break up
Lake-induced flexural stresses
What caused the acceleration of the Jakobshavn Isbrae in 1997?
Warm surface ocean waters caused by the prolonged NAO positive phase 1995-1995 that weakened the subpolar gyre and allowed for the arrival of warm waters from the Irminger Sea. Retreat and thinning rapid basal melt and the break-up of the ice tongue
How much ice is lost from the West Antarctic Ice Sheet?
At present, this was in 2014, 20% of total ice discharge was lost from WAIS
What is the retreat of the Pine Island Glacier controlled by?
Marine ice sheet instability due to a reversing slope bed. Enhanced melting at the bottom of the ice shelf due to Circumpolar deep water circulation, this causes thinning and decrease buttressing of the ice shelf which leads to the acceleration of the ice streams and the retreat of the grounding line into the glacier's trunk. The glacier trunk is situated in a deep subglacial trough.
Acceleration of the Pine Island Glacier
Bed rock topography deepening inland and the loss of the ice shelf
What is calving
Calving or mechanical loss of ice from the glaciers and the ice shelves is a component of the mass budget of a glacier system
Controls on the calving lossFlow acceleration and ice thinning. Increase calving fluxes, calving front retreats and increases the rate of ice delivered to the point.What makes a good receipe for calving failure?Large velocity gradients and steep crevasse penetration. Width is also very important tidewater glaciers and ice shelves at fjords and embayment widenings will result in huge calving losses (Benn, Wassen and Mottram, 2007)Where is ice loss seen at in Greenland and Antarctic Ice Sheets?In Greenland it is at all latitudes and on the grounding lines of Antarctica. Most profound changes are at the ocean margins (Pritchard et al., 2009)Where is dynamic thinning occurring in Greenland?Strong thinning is seen on the SE & NW ice sheet margins. Negative mass balance due to the discharge of tidewater glaciers (Pritchard et al., 2009)What caused the surge of the variegated glacier in 1964-65Cool spring- delayed the availability of the surface waters- terminationCause 1982-83 variegated surge?Changes in the subglacial hydraulic system. Switch to efficient discrete basal hydraulic system during the quiescent phase to a distributed one linked to the cavities overlying bedWhat triggers a jokulhlaupsThe sudden changes in the discharge/ pressure gradient in a subglacial drainage system beneath the ice dams due to surface melting which causes the unstable growth of conduitsWhat are the mechanisms of a glacier surgeHigh basal pressures deformation of till disruption of drainage system and basal sliding