It looks very like the 2017/18 Arctic sea ice maximum will beat the record low set only last year. At the moment (14th Feb) the anomaly stands at just 90.4% of the average for this day of the year, that’s 2.3% lower than it was this time last year, and equates to a massive 352,000 square kilometre less of sea ice (fig 1).
The fact that we are now in the grips of a SSW event doesn’t bode well for a late surge in sea ice as we approach the time of maximum in the Arctic. The mean date for the maximum is the 8th of March, and although unlikely, the maximum may have already occurred! The maximum so far this season occurred over a week ago now on the 5th (13.979 million square kilometres) which would make it extremely early, because the earliest maxima on record in the last 40 years occurred on the 21st of February in the years 1987, 1994 and 1996 (fig 2).
The Arctic Sea Ice extent is currently the lowest on record for any January 2nd since the satellite series started forty years ago. To be fair this season has been playing nip and tuck with last season (fig 2), but at the moment the 12.542 million square kilometers, which is 90.6% of the average for this day, is slightly lower than the 12.614 at the same time last year (fig 1). This news caught me out a little, because the last time I looked sea ice extent in the Arctic was holding up quite well. The reason behind this is probably down to the fact that the Arctic has been even milder than usual and had a bad Christmas, a bit like the sales figures at Debenhams.
There are a number of ship plumes visible in the 10 UTC visible satellite image of the southwest coast of Ireland. There’s an extensive layer of low stratus in that area, and some of the ships are streaming plumes of cloud back eastward in the W’SW breeze as they cross the Atlantic. I did read somewhere that the exhaust fumes of the diesel engines of container ships are the cause of some of the worst pollution excesses anywhere in the world.
There are a number of scientific reports concerning ship plumes that a quick Google search has just turned up.
Here are maps of SST anomalies just east of Newfoundland for the last three Decembers 2015 to 2017 (figs 1-3).
I know that it has some kind of bearing on the type of weather we get on our side of the Atlantic due to its influence on the jet stream and type of circulation patterns that we’re likely to see for the remainder of the winter. As far as I know negative SST anomalies in this region would favour blocking and more anticyclonic easterly weather, whilst positive anomalies, like they are at the moment, would mean increased mobility and storminess. So on the strength of the latest anomalies as high as +5°C (fig 3), our run of seven years without any snow lying in this part of Devon looks quite likely to be extended to eight.
I don’t have any papers I can include or quote from which explain this relationship in more detail, but I do have this recent comment in a newsgroup by Graham Davis who is more knowledgeable than most on the subject (I hope he doesn’t mind me quoting him).
“The reason for the recent lack of easterlies is the sea temperature anomalies in the North Atlantic haven’t been conducive. The important area in this regard is that immediately to the south of the Grand Banks. If this is colder than normal, the atmospheric pressure over Iceland tends to be higher than normal and lower than usual around the Azores. Conversely, a warm anomaly leads to below normal pressure in the southern Norwegian Sea and above average pressure in mid-Atlantic. These pressure patterns vary depending on time of year – due to changes in average jet-stream wavelength – and on the shape and position of the anomalies.
The last winter I can find with a cold pool in more or less the correct area during winter, although it was rather weak, was 2012-13 when Jan-Mar were anomalously easterly.
The predominance of the cold blob south of Greenland in recent years was suggested to be associated with a change in N Atlantic ocean currents. I pooh-poohed this idea at first but I’ve been coming round to it in the past couple of years. I’ve wondered whether this might be a sign that some of the Labrador Current is remaining on the surface and drifting eastwards instead of sinking below the Gulf Stream. This could be caused by a reduction in salinity of the current due to increased meltwater from the Greenland icecap entering the flow. If this is the case, it could be a sign that due to the bi-stable nature of the currents in the area we might be due for one of its flips and consequent sudden climate changes. The features of this change would be an intensification of the cold blob and a persistence of the warm anomaly south of 40N. This would mean we’d be stuck in almost permanent westerlies.“
The wake from Caroline is producing 35 foot waves at K5 at 08 UTC this morning (59.1° north 11.6° west) (fig 1). The cold front dropped the temperature almost 9°C in three hours on top of Cairngorm in the early hours (fig 2).
No boy scout worth his salt would have been as foolish to camp out on the Cairngorms last night, and if he had been, he certainly would never have got his tent up in a hurricane force 12 and gusts to 116 mph (fig 3).
A slight shift to the east overnight of the showers running down the Irish sea, also noticeable to the east are the band bands of very heavy wintry shower that are running down the east coast (fig 1). If you remember yesterday there were dual bands of showers running south down the Irish Sea, starting just west of the Isle of Man to western Cornwall, here are the estimated precipitation totals from 06 UTC on Thursday showing their track and extent (fig 2). You can still make out the dual bands that seem to split over Pembrokeshire.
This is no kind of scientific report about what goes into the formation and continuation of these bands, but someone did kindly point me to an article from the Quarterly Journal of the Royal Meteorological Society that does go into it some detail about them. Just for completeness, here are the latest SST anomalies from around the British Isles (fig 3), and you’ll notice that the SST down much of the central Irish Sea is running 1°C above the long-term average at the moment.
You can tell just by looking at these sea surface temperature charts since 2015 (figs 1-3) that there’s been considerable warming going on in the last two years. The cold anomaly that was a feature for so long in the central Atlantic is now less intense and much smaller a feature than it once was. It’s shifted and has been squeezed further northeast towards the southeast coast of Greenland and the opening of the Labrador Sea. The other notable difference that’s appeared in recent months is the area of warmer SST anomalies ~1500 km to the west of Portugal (42N 17W), a warm blob if you like.
The warm blob and this coming winter
To be honest I don’t have a clue if this warm blob will have the slightest effect on the weather in the British Isles this coming Winter. It would be nice to think that the area of warmer SST might weaken the Azores high in some way, and that might increase cyclonic development in the southeast Atlantic which will run northeastward towards Biscay – who knows. Looking at the actual MSLP anomalies (fig 3) for so far this month, it’s true that the Azores high is displaced further to the northeast, but all this has done has been to increase the strength of the zonal flow across the Atlantic. In fact everything seems to be enhanced in some way, if you look at the underlying anomalies (red dashed line) both highs and lows have been more intense in the first three weeks of November 2017 than usual.