RESPONDER Profile picture
Apr 8, 2018 13 tweets 15 min read Twitter logo Read on Twitter
In 2013 @IPCC_CH concluded “Surface meltwater, although abundant on the #Greenland ice sheet, does not drive significant changes in basal lubrication that impact on ice sheet flow”. Could the opposite be emerging as a new paradigm? Thread 👇 1/12. Read and tweet. #climateclimate
The #IPCC #5AR statement (above) refers to efficient evacuation of meltwater in large channels, which can slow down the #ice flow by removing water that otherwise would lubricate and promote faster sliding over the bed. 2/12…
Evacuation of meltwater in efficient channels explains why #ice flow in some regions of #Greenland has slowed down despite year-on-year increases in air temperature and surface melting. But how widespread are those observations? 3/12…
A closer inspection of #ice flow shows that the stabilising effect from channels vanishes at around 1000 m elevation.…
Why? Thick ice promotes channel closure while flatter surface may inhibit channel opening to begin with. 4/12…
“Houston we have a problem!” The vast majority (around 90%) of #Greenland’s supraglacial ‘melt lakes’ form at elevations above 1000m. 5/12…
Many of these lakes drain in rapid events, which form conduits for the transfer of surface meltwater directly to the base of the ice sheet. These conduits can stay open for weeks and sometimes months. 6/12…
Rapid ‘lake drainages’ are not isolated incidents. When one lake drains, water spreads under the #ice sheet, lubricating its flow. Faster flow produces fractures, causing more lakes to drain, some as far as 80 kilometres away #CascadingDrainage. 7/12
#CascadingDrainage is a recently identified chain reaction mechanism. It explains why lakes in compressive basins drain when fractures form by extension, why precursory activity (e.g. uplift) occurs before drainage, and why lakes drain in clusters. 8/12
#CascadingDrainage explains why @sarahwcooley @scottpolar found high-elevation lakes on the #Greenland #ice sheet to be as likely to rapidly drain as lakes lower down. The hypothesised elevation limit from previous work has been rejected. 9/12…
#CascadingDrainage also explains why fractures form on the interior #ice sheet (left graphic) and why ice flow there has been steadily increasing (right graphic) in a trend that opposes the slowdown at lower elevations. 10/12
Observations show that lakes on #Greenland #ice sheet are becoming larger and more numerous, progressively expanding to higher elevations.…
In five decades, lakes are predicted to expand to 2200 m elevation.….
#climatechange 11/12.
Based on evidence, it is logical to conclude that the #Greenland #ice sheet is more vulnerable to climate change than portrayed by @IPCC_CH in #AR5.
To read about a more vulnerable Greenland ice sheet:
Now you know what @ERC_Responder is about. #AR6 Our aim is understand how hydrological networks at the base of #Greenland #ice sheet evolve over seasons and over multiple years, and how that evolution impacts on ice flow
on the interior and at the coast.

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