Citations
IPCC, 2007
Oceanic forcing may be of particular concern in the near future, as model predictions suggest that ocean temperatures around the GIS may warm by 1.7–2C by 2100
Arctic warming is expected to far exceed the global average and is forecast to reach up to 7 degrees by 2100
The Greenland Ice Sheet contains 7m of sea level rise in comparison to Antarcticas 56m
Joughin et al
2008
2010
2012
In both northern and southern Greenland sea ice concentrations at Jakobshavn Isbrae appear to influence the timing and nature of calving events, but this occurs on seasonal, as opposed to decadal, timescales
Joughin et al., 2010 showed that mass loss is concentrated to the coastal markings, predominantly MTOGs
Greenland and Antarctica are losing mass at an accelerating rate, much of which is due to ocean forcing predominantly of floating ice shovels
Hanna et al., 2006
Benn and Evans, 2010
MTOG defined as a channel of fast-moving ice that drains an ice cap or ice sheet and terminates in the ocean, at either a floating or grounded margin
Greenland is the larges ice mass in the Northern Hemisphere, containing 10% of the Earth's fresh water at 1,736,000km2
Calving at the termini of MTOGs account for over half of the total ice loss so it can have major impacts on SMB
Greenland climate shows large variability on terms of temperature and precipitation from year to year
Greenland ocean and surface temps are rising
Arctic air temp has risen substantially since the 90s
Van de Broeke et al., 2009
Arctic ice masses have rapidly lost mass since the mid-1990s due to a combination of negative SMB and accelerated discharge from marine- terminating glaciers
Recent mass deficits have been attributed to both increased marine-terminating outlet glacier discharge and to a more negative surface mass balance (SMB), primarily resulting from increased surface melting relative to accumulation
Zwally et al., 2002
as believed in land ice would not speed up on short scales
Zwally et al, 2002 proved this wrong with research at Swiss Camp (The equilibrium line at the central west) showed speed ups in the early summer (Zwally effect)
Swiss Camp is 1200m thick and below amp implying reactivation of englacial drainage systems each melt season
Zwally effect is increased surface melt causes water draining into the ice through crevasses or cracks and then reaching the ice/bedrock interface
The weight off meltwater on the ice surface can also cause cracking due to stresses
Cases of lakes melting and large volumes of water reaching the interface have shown hydraulic jacking of the ice detaching away from the bedrock meaning friction is reduces hence surging behaviour or simply just a velocity increase
The excessive volume of meltwater can travel through the ice through cracks or through forming pseudo meltwater channels on the surface that feed into subglacial drainage
Hughes, 1986
Jakobshavn Effect
Jakobshavn Isbrae on the Greenlandic West Coast
The Jakobshavns Effect is a group of positive feedback mechanisms which allow Jakobshavns Glacier to literally pull ice out of the Greenland Ice Sheet at a rate exceeding 7 km
Positive feedback mechanisms that sustain the rapid ice discharge rate are ubiquitous surface crevassing, high summer rates of surface melting, extending creep flow, progressive basal uncoupling, progressive lateral uncoupling, and rapid iceberg calving.
Ice sheet thinning allows the ice to become more buoyant, eventually leading to a grounded ice sheet to start to float. This leads to reduced friction at the base and flow increase and a non-linear response. Sudden changes in friction can also be caused when the glacier passes pinning points
Carr et al., 2013
Until recently it was assumed that ice masses respond to climatic/oceanic forcing over millennia however the past 2 decades of observations have proved this wrong
Climatic forcing, ocean forcing and sea ice concentrations are the three factors impacting MTOG behaviour
MTOGs dynamically change over annual time scales
The response of marine- terminating Arctic outlet glaciers to climatic/ oceanic forcing remains a key area for future research and is crucial for accurate prediction of near-future sea level rise and Arctic ice mass response to climate warming.
Results from the GIS have highlighted the substantial variation in marine-terminating outlet glacier response to climatic/oceanic forcing
Numerical modelling results have improved our understanding of marine-terminating outlet glacier behaviour, but remain a key area for future development
enhanced submarine melting may cause grounding-line retreat at floating and grounded margins, potentially resulting in further ungrounding and the development of positive feedbacks if retreat occurs into deeper water
The processes controlling warmer water flows are still largely a mystery