CNN are not the only media outlets to report on this years’ record low sea ice around Antarctica in apocalyptic terms, other media extremists are available. For Sky News it’s the accelerating melt of polar regions. For the BBC “There is now less sea-ice surrounding the Antarctic continent than at any time since we began using satellites to measure it in the late 1970s.” All this is technically true, but misleading. When it’s put into context one sees a different picture.
So let’s have a look at the actual satellite data of Antarctic sea ice collected monthly since 1979. The NSIDCgives two data sets for what it calls i) sea ice extent, and ii) sea ice area. So let’s examine both of them.
The first graphs is sea ice area, the second sea ice extent.
From the empirical data it is evident that there is hardly any change of sea ice over the 44-year time span. Since 2016 there is a dip with possibly more variability (of which more later), and the lowest month (February) does show a record low, but by hardly anything (and also look at the data for 1992). Does this actual data look like the beginning of the end to you? Where is CNN’s 90% loss or Sky News acceleration?
The Danish Meteorological Institute (DMI) also performs daily simulations of how much ice or water the Ice Sheet loses or accumulates. Based on these simulations, an overall assessment of how the surface mass balance develops across the entire Ice Sheet is obtained (Fig. 4).
At the end of the 2018 season (31 August 2018), the net surface mass balance was 517 Gt, which means that 517 Gt more snow fell than the quantity of snow and ice that melted and ran out into the sea. This number only contains the balance at the surface, and thus not the total balance, which also includes melting of glaciers and calving of icebergs.
Although the total SMB (Surface Mass Budget) for the 2016-2017 and 2017-2018 seasons are similar, development during the two seasons has been very different. Last year, the season began by gaining a lot of mass during the winter, whilst the development in SMB from the summer onwards reflected the long-term average. During the 2017-2018 season, SMB remained in line with the average from 1981-2010 until the summer, after which the development in SMB was higher than average.
La géologie, une science plus que passionnante … et diverse