bluewave

Recent cooler temps and stronger polar vortex let 2017 fall a little behind 2007 over the last few days.

Early dip near freezing with the strong polar vortex similar to 2014 and 2013.

It could also be related to why the Siberian October snow signal hasn't worked in recent winters with the stronger PV and more +AO/+NAO.

We missed our chance to beat 2012 when the strong dipole pattern of 2007-2012 failed to emerge in June. So the 2012 extent record will remain safe another year. The HadGem model did a great job back in 2012 showing a slower rate of loss vs the extreme 2005-2012 loss rate. I am wondering if the dramatic dipole reversal following the historic 2007-2012 rapid melt seasons is a result of the weaker AMOC? http://nsidc.org/arcticseaicenews/ In the far northern Atlantic, warm water flowing northward from the tropics is cooled by the atmosphere, becomes denser, and eventually sinks to great depths. The descending water is key in driving a sub-surface and surface ocean circulation system called the Atlantic Meridional Overturning Circulation (AMOC), which is part of the global ocean conveyor belt of heat and salinity. Where the Atlantic water sinks has a very important effect on the climate of Northern Europe; the heat that the ocean loses to the atmosphere is what keeps Northern Europe quite warm relative to its latitude. For example, Amsterdam is at the same latitude as Winnipeg, Canada, but experiences much warmer winters. Based on a recent modeling study, Florian Sévellec and colleagues propose that the ongoing loss of Arctic sea ice may disrupt the AMOC. The sea ice loss leads to a freshening of the northern North Atlantic and stronger heat absorption at the surface. This means that waters in the northern North Atlantic are less dense than they used to be, which has the effect of providing a cap, or lid, that may inhibit the northward flow of warm waters at the surface and the eventual sinking of these waters. The authors suggest that the Arctic sea ice decline may help to explain observations suggesting that the AMOC may be slowing down, and why there is a regional minimum in warming (sometimes called the Warming Hole) over the subpolar North Atlantic.

The median of the 36 September mean extent forecasts is slightly below last September.

It will be interesting to see if the September 2012 low extent record can remain in place into the early 2020's. Or if the dipole pattern makes a return in 18-19 finally allowing a new record minimum to be set. Not sure many in September 2012 though it would take so long to break the record.

The rate of losses did slow post 2012 relative to the rapid 2005-2012 decline rate. But the long term downward trend will continue. https://theconversation.com/why-arctic-melting-will-be-erratic-in-the-short-term-35969 A new study I co-authored with a team of Canadian and American scientists, published in Nature Climate Change, highlights that the recent slower melt is a temporary, but not unexpected, deceleration. The complex climate models used to make projections of future climate also exhibit similar periods of little change and more rapid change in Arctic sea ice. The recent trends are well within the range of these expectations. We might even see a decade or more with little apparent change in sea ice. The causes of these fluctuations in melt rate are still being explored. Onesuggestion is that slow variations in Atlantic sea surface temperatures are involved. More observations of the Arctic ocean, atmosphere and sea ice would help answer this question. An ice-free future? When will the Arctic be ice-free – or equivalently, when will the ball reach the bottom of the hill? The IPCC concluded it was likely that the Arctic would be reliably ice-free in September by 2050, assuming high future greenhouse gas emissions (where “reliably ice-free” means five consecutive years with less than 1 million km2 of sea ice). We expect the long-term decline in Arctic sea ice to continue as global temperatures rise. There will also be further bounces, both up and down. Individual years will be ice-free sometime in the 2020s, 2030s or 2040s, depending on both future greenhouse gas emissions and these natural fluctuations.

Yeah, the HadGEM1 did a great job. https://www.the-cryosphere.net/7/555/2013/ Mechanisms causing reduced Arctic sea ice loss in a coupled climate model A. E. West, A. B. Keen, and H. T. HewittMet Office Hadley Centre, Exeter, UK Received: 09 May 2012 – Discussion started: 18 Jul 2012 Revised: 04 Feb 2013 – Accepted: 18 Feb 2013 – Published: 26 Mar 2013 Abstract. The fully coupled climate model HadGEM1 produces one of the most accurate simulations of the historical record of Arctic sea ice seen in the IPCC AR4 multi-model ensemble. In this study, we examine projections of sea ice decline out to 2030, produced by two ensembles of HadGEM1 with natural and anthropogenic forcings included. These ensembles project a significant slowing of the rate of ice loss to occur after 2010, with some integrations even simulating a small increase in ice area. We use an energy budget of the Arctic to examine the causes of this slowdown. A negative feedback effect by which rapid reductions in ice thickness north of Greenland reduce ice export is found to play a major role. A slight reduction in ocean-to-ice heat flux in the relevant period, caused by changes in the meridional overturning circulation (MOC) and subpolar gyre in some integrations, as well as freshening of the mixed layer driven by causes other than ice melt, is also found to play a part. Finally, we assess the likelihood of a slowdown occurring in the real world due to these causes.

I think some people are coming into each season thinking that it will be a continuation of the 2007-2012 mega dipole pattern. But outside July 2015, the summer Arctic pattern did a complete reversal following that 2012 record breaking summer. It was like the 2012 extremes of low sea ice extent and Greenland melt flipped a switch over to a new regime. Maybe some type of mini summer Arctic D-O event?

I agree. The coming cooldown across the CAB should keep 2017 behind the 2012 extent over the next the next 10 days. 2012 will probably run away from 2017 in early August when the steep 2012 drop occurred. With the exception of July 2015, a cooler polar vortex has dominated the Arctic summers from 2013-2017.

Yeah, and how much colder this summer is in Greenland compared to 2012. http://polarportal.dk/en/nyheder/arkiv/nyheder/bringing-harmonie-to-the-greenland-ice-sheet/ Martin Stendel, Polar Portal leader, agrees. “This year has been extremely unusual, with a snowy winter and then a cool period at the start of this month. It’s extremely important we get the surface mass balance right.” The period from the 27th June to the 5th July saw days with close to zero or even slightly positive SMB (a net gain in mass) as well as a record low temperature recorded at the DMI weather station at Summit -33.0 °C. This weather along with the snowfall in early June, and following from the heavy snow in the Autumn, has led to a relatively high surface mass balance for the time of year and an unusually bright and reflective ice sheet, as shown in the albedo anomaly map on the Polar Portal (and below). Professor Jason Box of GEUS explains “when we see cold snowy conditions like this in the summer time it brings melt to a halt. The fresh snow is bright and reflects sunlight whereas in normal years dark bare glacier ice is usually exposed at this time of year and so melt rates are strong. This is why we track the albedo through the year to see how much melt we can expect”. So far this summer there has been less melt than usual. As DMI weather forecaster Jesper Rosberg explains, “we have seen a persistent positive North Atlantic Oscillation this summer and the jet stream has been very far south of Greenland with very cold air over the ice sheet, so the precipitation falling this summer has mostly been snow, rather rain. ” The cold and snowy conditions have been hindering scientific fieldwork this summer. But there are still several weeks of the ablation season left and the weather for the rest of July and August will determine the surface mass balance of Greenland this year. As far as DMI scientists know this is the first time that the SMB of the Greenland ice sheet has been calculated with such a sophisticated model in near real-time and it’s all the more interesting since we have snowfall interfering with melt.

On JAXA and NSIDC extent we probably missed to our chance to beat 2012 with the stronger PV pattern from June into early July. It even fell a little behind last year in recent days.

Either natural variability or the early emergence of the CCSM4 summer pattern in response to climate change. The NH summer circulation since 2013 bears a strong similarity to the presentation below. https://ams.confex.com/ams/94Annual/webprogram/Paper235210.html

Interesting increase in NH snow cover for June compared to recent years. The highest in over a decade.

After record breaking -AO and KB block last fall, the PV has mostly been in charge. While we had some transient Arctic blocking episodes, but the PV quickly makes a return.

It's funny how the pattern reversed right after the paper was published. http://onlinelibrary.wiley.com/store/10.1029/2012GL053268/asset/grl29604.pdf;jsessionid=F7950891CB18B3DB5580C02EC912A4A1.f01t03?v=1&t=j4ppf2qo&s=29436c163ab48e25e8f4989445de41091a8d6ccd&systemMessage=Wiley+Online+Library+'Journal+Subscribe+%2F+Renew'+page+will+be+down+on+Wednesday+05th+July+starting+at+08.00+EDT+%2F+13.00+BST+%2F+17.30+IST+for+up+to+75+minutes+due+to+essential+maintenance. Thus we can say that a six year run of near one standard deviation negative excursions (2007–2012) is unique in the 63 year record. To further test the significance of the 2007–2012 AD patterns we randomly generated 10,000 time series, each with 63 points to match the observed time series and with a normal distribution without autocorrelation. For this simple calculation, the chance for having five consecutive values with a negative AD of magnitude greater than 1.0 standard deviation units in a sample size of 63 is rare, less than 1 in a 1000.

While the overall annual temperature trend is an unmistakable up, it would be interesting to know what changed after the 2012 summer. To get a 6 year historic stretch of dipole patterns during the summer and then a reversal is pretty extreme 500 mb behavior.

June officially continues the post 2012 pattern of a more active polar vortex and cooler temps.You can see the long range ensembles continuing this general pattern right into July.

You are right. That was probably the better example of Volume vs extent divergence. 2007 was the year of the mega dipole. Remarkable how a version of the summer pattern repeated much of the time until 2012 and then abruptly reversed.

It's interesting how big a difference the extents can vary with similar volume depending on weather conditions. We saw the divergence between 11 and 12 extents on similar volume due to the much more hostile weather pattern in 12.

JAXA looks like it's on target to finish very close to last year if there is an average 2007-2016 melt rate for the rest of the summer.

IMHO the 2005-2007 period pretty much reset the whole Arctic background state. Arctic amplification really took off at that time when the September avg extents started regularly falling below 6 million sq km on NSIDC. We didn't even need a 2012 record minimum the last few years to set the extreme Arctic warmth records.

We would need a solid dipole pattern to lock in to have a chance of challenging 2012. Otherwise, it's going to be another year that the 2012 record holds. Seems like the really extreme Arctic conditions for the most part since 2012 have been during the winters instead of the summers from 2007-2012.

If this cooler pattern continues, then it might not really matter if we know the exact volume for sure. 2012 and 2011 weren't all that different on volume in August and September. But the 2012 record warmth with the weather pattern made all the difference between the two extent finishes in September. This June is continuing the post 2012 stronger polar vortex pattern vs the 2007-2012 raging dipole regime. We would need a July 2015 rapid reversal to really accelerate the melt. But that kind of reversal isn't showing up in the longer range guidance as of yet. Even Greenland is enjoying a below average melt compared to recent years.

PIOMAS actually pulled back closer to the pack the last few weeks.