I keep vigil.
Lots of activity on the world's largest reserve of fresh water.
The number of meltwater lakes on the surface of the East Antarctic Ice Sheet is more significant than previously thought, according to new research.
A study led by Durham University, working with researchers from Lancaster University, discovered more than 65,000 supraglacial lakes using high-resolution satellite imagery covering five million square kilometres of the ice sheet, including areas where surface melting was previously thought to be less intense.
This is the first time that researchers have been able to map the widespread distribution of lakes across a vast area of the East Antarctic Ice Sheet – the world’s largest ice mass – within a single melt year.
Although most of the ice sheet is incredibly cold, with temperatures plummeting to below -40 degrees Celsius in winter, summer temperatures can often reach above zero and cause surface melting. The study shows that meltwater lakes are forming in most coastal areas of the ice sheet, suggesting that East Antarctica could be more susceptible to the effects of a warming climate than previously thought.
The findings are published in the journal Scientific Reports.
Supraglacial lakes (SGLs) form when meltwater ponds in depressions on the surface of a glacier or ice sheet1. They range in size from a just a few metres to tens of kilometres in area1,2,3,4 and they play an important role in an ice sheet’s mass balance. Firstly, they decrease the ice surface albedo and increase the absorption of incoming solar energy, thereby setting up a positive feedback that may further enhance melting5,6,7. Secondly, their rapid drainage has been implicated in the collapse of floating ice shelves8,9,10,11,12, which can then cause increased ice discharge from tributary outlet glaciers13,14. Thirdly, the drainage of SGLs to the bed of grounded ice in Greenland has been linked to transient speed-ups in ice velocity15,16,17,18,19. This process has yet to be observed in Antarctica, although it has been noted that future warming could increase the connectivity between surface and basal hydrological systems20.
In summary, SGLs occur in most low elevation, gently-sloping marginal areas of the EAIS (East Antarctic Ice Sheet), which reflects the fact that the ice sheet margin extends to relatively low latitudes where summer temperatures are high enough for surface melting to occur20,27,28,40. However, the distribution of lakes is highly variable and they occur in clusters of higher density (Fig. 1) that do not obviously correlate with the areas of highest melt obtained from radar backscatter27,28 or coarse-resolution (e.g. 27 km) regional climate modelling40,42. Rather, clusters of high lake density reflect the interaction between local-scale climatic controls and ice surface characteristics, including regional-scale wind patterns, ice surface albedo and topography, and firn air content and thickness32,42,49. Thus, the complex interplay of these local-scale processes makes it difficult to predict the location of SGLs based only on the current generation of Antarctic-wide observations and modelling of surface meltwater production.
'Our research shows for the first time that surface meltwater is getting beneath glaciers in the Antarctic Peninsula – causing short bursts of sliding towards the sea 100 per cent faster than normal,' said Jeremy Ely, Independent Research Fellow at the University of Sheffield's Department of Geography and author of the study.
'As atmospheric temperatures continue to rise, we expect to see more surface meltwater than ever, so such behavior may become more common in Antarctica.
'It's crucial that this factor is considered in models of future sea-level rise, so we can prepare for a world with fewer and smaller glaciers.'
According to Pete Tuckett, who made the discovery while studying for his Masters in Polar and Alpine Change at the University of Sheffield, the research is the first-of-its-kind to focus on Antarctica.
'The direct link between surface melting and glacier flow rates has been well documented in other regions of the world, but this is the first time we have seen this coupling anywhere in Antarctica.
'Given that atmospheric temperatures, and hence surface melt rates, in Antarctica are predicted to increase, this discovery could have significant implications for future rates of sea-level rise.'
Meanwhile, Antarctica glaciers have been shedding ice bergs at a rapid pace.
— Stef Lhermitte (@StefLhermitte) September 19, 2019
Dis and dat.
— Ã Â¦ÂÃ Â§ÂÃ Â¦ÂÃ Â§ÂÃ Â¦Â°Ã Â¦Â¾Ã Â¦Â® Ã Â¦Â¸Ã Â§ÂÃ Â¦Â¬Ã Â¦Â¾Ã Â¦Â®Ã Â§Â (@From_Himalaya) August 12, 2019
Pine Island glacier is on the verge of calving yet another major iceberg, once it does it will be the seventh “large-calving event from this glacier since 2001”.
— Pine Island Glacier (@AntarcticPIG) October 27, 2018
The basic theory of crevasse formation suggests that crevasses initiate at or near the surface. However, due to variations in stress with depth, it has been suggested that it is possible for crevasses to initiate at depths of 10–30m. From December 2006 to January 2007, hot-water drilling on Pine Island Glacier, West Antarctica, was found to trigger crevasses. Satellite imagery and field investigations in 2008, including ice cores, radar and GPS, revealed that these formed a new band of arcuate (curvilinear) crevasses around 70 km long and 100 m deep. This new band is located 10 km upstream from the previous limit of the arcuate crevasse zone. The crevasses were triggered on drilling through an exceptional ice layer at >20m depth. Ice layers within the firn will change both the strength and stress intensity. As the firn changes spatially and temporally (e.g. with the burial of an ice layer), it is possible for the position of crevasse initiation to change whilst the along-stream strain-rate profile remains constant. However, the main cause of an upstream migration of the arcuate crevasse zone on Pine Island Glacier is still likely to be an increase in strain rate.
The most recent calving event occurred at Amery glacier in East Antarctica.
— Bert Wouters (@bert_polar) September 30, 2019
The Brunt ice shelf survived the summer solstice and is poised to shed an iceberg twice the size of New York City at any moment. The ice shelf is monitored by the British Antarctic survey.
Thank you for reading.