In full the report about 2019 - not found on the DMI website, but here..
https://skepticalscience.com/how-greenland-ice-sheet-fared-2019.htmlneed 2 months more GRACE-FO data and the story will be complete- early December with luck. It will test their estimates of mass loss from calving & ocean seawater contact melting_________________________________________________________
How the Greenland ice sheet fared in 2019
Posted on 7 October 2019 by Guest Author
This is a re-post from Carbon BriefDr Ruth Mottram, Dr Martin Stendel and Dr Peter Langen are climate scientists at the Danish Meteorological Institute (DMI) in Copenhagen, which is part of the Polar Portal. Dr Andreas Ahlstrøm and Dr Kenneth D. Mankoff are chief research consultant and senior scientist at the Geological Survey of Denmark and Greenland, respectively.As the end of August sees summer shift into autumn for the northern hemisphere, it also marks the end of the melt season for the Greenland ice sheet.
The advent of a new season is the traditional time for our annual look back at the year gone by and what it tells us about the state ice sheet.
Our estimates show that the surface of the ice sheet gained 169bn tonnes of ice over 2018-19 – this is the seventh smallest gain on record.
And using new satellite data, we show that – once all ice sheet processes are factored in for the past year – the Greenland ice sheet saw a net decline of 329bn tonnes in ice.
Surface processes
While western calendars show another four months before a new year, scientists generally consider the beginning of September as the start of a new annual cycle for the Greenland ice sheet.
This yearly pattern sees the ice sheet largely gain snow from September, accumulating ice through autumn, winter and into spring. Then, as the year warms up into late spring, the ice sheet begins to lose more ice through surface melt than it gains from fresh snowfall. This melt season generally continues until the end of August.
The contrast between snow gains and ice losses at the surface over the whole year is known as the “surface mass balance” (SMB). The chart below shows the SMB for 2018-19 on individual days (top) and cumulatively across the year (bottom). The blue lines show 2018-19 data and the grey line shows the long-term average. The lower chart also shows the record low year in 2011-12 (red line) for comparison.
click to seehttps://www.carbonbrief.org/wp-content/uploads/2019/09/SMB_curves_LA_EN_20190831.pngDaily (upper chart) and cumulative (lower) surface mass budget of the Greenland ice sheet, in billion tonnes per day, and billion tonnes, respectively. Blue lines show 2018-19 SMB year; the grey lines show the 1981-2010 average; and the red line in lower chart shows the record low SMB year of 2011-12. Credit: DMI Polar Portal.
This year has been an unusual one. It has been consistently drier than normal, which is reflected in the below-average gains in snow throughout the year. And the summer has been warm with some periods of very high melt.
Overall, while the 2016-17 and 2017-18 seasons saw above-average gains in ice at the surface, the SMB in 2018-19 ends as the seventh lowest on record. The total accumulated SMB was only 169bn tonnes at the end of the year. This means that nine of the Top 10 lowest SMB years have occurred in the last 13 years in our record that goes back to 1981.
Total losses
It is important to remember that SMB is always positive at the end of the year – more snow falls on the ice sheet than melts at the surface. But the ice sheet also loses ice by the breaking off, or “calving”, of icebergs and from ocean melting at its edge. Therefore, the extra snowfall is needed in order to compensate for these processes.
Observations collected by the European Space Agency’s Sentinel-2 satellite measure ice velocity of outlet glaciers around the edges of the ice sheet. By measuring how quickly the ice moves into the ocean we can work out how much ice is being lost by calving and ocean melting.
On average between 1986 and 2018, the ice sheet discharges about 462bn tonnes per year. This year our analysis suggests Greenland discharged around 498bn tonnes of ice.
Factoring in these additional processes, we can calculate the total mass budget for the ice sheet for the year. For 2018-19, we estimate the ice sheet has seen a total net ice loss of around 329bn tonnes.
Data from the GRACE satellites indicate that Greenland lost an average of approximately 260bn tonnes of ice per year between 2002 and 2016, with a peak of 458bn in 2012. Clearly, the loss of 329bn tonnes we estimate this year is significantly above the 260bn tonne long-term average, but we have not broken the highest record for ice loss in a year.
Long, dry summer
The high losses this year were from a combination of factors. The SMB year started in September 2018 with a long dry period – a much drier than usual winter over most of Greenland (only the south-east had more snow than usual). This left the ice sheet with only a thin protective cover that melted quickly in the lower areas when the melt season got going on the 30 April.
In fact, 2019 saw the second earliest start to the melt season on record – after 2016 – when an unusual spike in melting occurred in early April. The summer that followed was very long, dry and warm, with substantial melting all over the ice sheet and especially in the west and north.
The map below shows how the SMB at the end of the 2018-19 season compared with the long-term average. The shading indicates higher (blue) and lower (red) gains in ice than usual over the year. You can see that the majority of the ice sheet gained less ice than average.
click to seehttps://www.carbonbrief.org/wp-content/uploads/2019/09/SMB_map_LA_acc_EN_20190831.png