...Three related points:Here are the professionals at the DMI with their observations, via ScienceNordic, October 27:
1) If you remember your geologic timescales the divisions of time on earth run from "eons which split into eras, which break into periods, which divide into epochs and then all the way down to ages." That's from Inverse who note the powers that be decided to call the present age the Meghalayan referring to the drought-caused worldwide collapse of civilizations 4200 years ago rather than the much-championed Anthropocene (human influenced) age.
2) The last two years something changed in Greenland and the ice mass is growing quite fast. Whether this is an important event or a natural perturbation remains to be seen.
3) Until that point is sorted out we should probably add the wobble to the list of things caused by global warming (many links have rotted since the last time we posted the list, we'll try to update sometime before the end of the Meghalayan):...
It's time for the Greenland ice sheet's annual health report, brought to you by scientists from the Danish Meteorological Institute and Polar Portal.
The end of August traditionally marks the end of the melt season for the Greenland ice sheet as it shifts from mostly melting to mostly gaining snow.
As usual, this is the time when the scientists at DMI and our partners in the Polar Portal assess the state of the ice sheet after a year of snowfall and ice melt. Using daily output from a weather forecasting model combined with a model that calculates melt of snow and ice, we calculate the “surface mass budget” (SMB) of the ice sheet.
This budget takes into account the balance between snow that is added to the ice sheet and melting snow and glacier ice that runs off into the ocean. The ice sheet also loses ice by the breaking off, or “calving”, of icebergs from its edge, but that is not included in this type of budget. As a result, the SMB will always be positive – that is, the ice sheet gains more snow than the ice it loses.
For this year, we calculated a total SMB of 517bn tonnes, which is almost 150bn tonnes above the average for 1981-2010, ranking just behind the 2016-17 season as sixth highest on record.
By contrast, the lowest SMB in the record was 2011-2012 with just 38bn tonnes, which shows how variable SMB can be from one year to another.
We must wait for data from the GRACE-Follow On (GRACE-FO) satellite mission before we know how the total mass budget has fared this year – which includes calving and melting at the base of the ice sheet. However, it is likely that the relatively high end of season SMB will mean a zero or close-to-zero total mass budget this year, as last year.
The period 2003-2011 has seen ice sheet losses on Greenland averaging 234bn tonnes each year. The neutral mass change in the last two years does not – and cannot – begin to compensate for these losses. The comparison here does show that in any given year, the mass budget of the ice sheet is highly dependent on regional climate variability and specific weather patterns.
SMB through 2017-18 (top) and 2018-19 (bottom) shown as blue lines.
Grey
lines show the 1981-2010 average and red shows the record low
of
2011-12. (Credit: DMI Polar Portal)
Fresh snowRelated at ScienceNordic, October 8:
Although this year has seen similarly high SMB values to 2016-17, the evolution of the budget through the year has been quite different.
You can see how the two years compare in the charts below. Whereas 2016-17 (blue line in upper chart) started with a large mass gain in winter and then tracked in line with the long-term average, the SMB in 2017-18 (blue line in lower chart) had been just about average all year until the summer.
***Snowfall over the 2017-18 winter was close to the long-term average and although there were heavy snowfalls – especially in the east of Greenland – there were no record storms as in the previous winter, when we saw the arrival of former tropical hurricanes Matthew and Nicole in October 2016.
The maps below show the gains (blue shading) and losses (red) in ice mass by August for 2017 (left) and 2018 (right). The eastern part of Greenland has had above average SMB in both seasons while the western part has seen considerable losses.
The melt season started as normal in May, but it was relatively cold month – the Summit Station at the very top of Greenland even set a new record low for the month when it dropped to -46.3C on 9 May. In addition, late spring snowfall in early June restricted melting and the “ablation” season – when ice melts and runs off the ice sheet into the ocean – did not really get going until the last week in June....MUCH MORE
How kite skiing and weighing snow helps improve projections of sea level rise
