Tuesday, July 12, 2016

Another Result on Greenland's Melt Rate

There's a new paper in GRL by Malcolm McMillan et al, "A high-resolution record of Greenland mass balance." They studied the period 2011-2014, mapping "recent Greenland Ice Sheet elevation change at high spatial (5 km) and temporal
(monthly) resolution." (They even modeled the firn, the granularity of the snow, because it influences the backscattered radar echo.) Their rate of ice loss, -269 Gt/yr, is close to other recent values, and (added 7/7) equivalent to a global mean sea level rise over this period of 0.74 ± 0.14 mm/yr, "approximately double the 1992–2011 mean." They find regions where glacier velocity has increased significantly in recent years -- "...only 0.9% of the total ice sheet area, have contributed more than 12% of the total mass balance during our study period."

But they don't seem to find any downward acceleration in these years:

They don't calculate an acceleration in their paper.... Has melt acceleration stopped, or is this just a blip upward? I would be surprised if it has stopped -- this latest paper only covered a 3-year period, while the others (below) were all over 10 years. That makes it a difficult to detect an acceleration -- just look at any 3-year interval on their graph -- the all look straight.

In any case, here is my collection:

Note 7/13: this is a change from the earlier table; the "--" means the four years in the McMillan et al study was too short an interval to reliably detect an acceleration. See here

Added 7/13: I give some remarks and clarifications by Malcolm McMillan here.

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