I have returned from my holidays and the children are back at school. So I guess summer is over and it’s time for my annual check on how the Arctic sea ice is doing. … What?
The summer minimum of Arctic sea-ice extent will probably be reached in the next couple of weeks but already the previous minimum sea-ice extent has been undercut by more than a half-a-million square kilometres. Currently there are only around 3.5 million square kilometres of sea ice. The previous minimum value in 2007 was 4.2 million square kilometres. In the 1980′s – when I was twenty-something and unconcerned about Climate Change – a more typical figure would have been 7 million square kilometres of sea ice.
The graph at the head of the page shows the data which is collated from spreadsheets available here, here (old data) and here (new data). A multitude of graphics are available at the US Snow and Ice Data Center.
- First we need to remind ourselves that nobody – and I mean nobody – knows what is going to happen next. However it looks like the people modelling the volume of arctic sea ice have their models just about right. Even while the sea-ice area was relatively stable, the ice thickness was probably declining. Once a minimum thickness is reached, the coherent ice sheet is broken apart by weather. The reflectivity of the surface then changes and much more solar radiation is absorbed. It is interesting to note that in contrast with the recent changes in summer sea-ice, the sea-ice winter maximum appears be only declining rather slowly.
- If the volumetric modelling is correct, then as I mentioned previously, over the next few years – and I mean years and not decades – summer ice in the Arctic will reduce in extent dramatically. It is quite plausible that even by 2020 we could have a few days each year in which there is no coherent ice sheet in the Arctic.
- Once the sea-ice melts in summer then each year the number of days that the ice melts will increase and summer ocean surface temperatures will begin to rise above zero. It is not clear that we will ever reach a situation in which sea ice will not form in winter – but it is possible. Remember that summer in the Arctic is more intense than anywhere else on Earth. It is a shocking fact that during each day of the Arctic summer, more solar energy falls on each square metre of sea or ground in the Arctic than ever falls on a square metre of ground in the tropics or deserts.
In my opinion this data speaks more eloquently than either myself, or reams of scientific papers discussing global temperature. This data speaks eloquently and it is saying very clearly – “something dramatic is happening in the Arctic: be concerned.”
Tags: Arctic Sea Ice