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Dear Readers The impact of increasing global temperatures over the last forty years on Arctic sea-ice cover is clear: There has been a consistent decline in sea-ice extent compared to the long-term normal (see here for an illustration: http://nsidc.org/soac/sea-ice.html#seaice). The possibility of the Arctic Ocean becoming ice-free in summer, then remaining so into the winter is one that is of increasing concern for remote communities on the Arctic coastline and for wildlife. Less appreciated, perhaps is how an Arctic Ocean free of pack-ice year round would impact upon the prevailing (and possible extreme) weather- conditions further afield. It is certain that the loss of Arctic sea-ice would occur in the context of global temperatures just 2.5 to 3C above those of today. As the Arctic warms and the edge of the pack-ice recedes north of Spitzbergen the ice-free water absorbs heat from the Sun rather than reflecting it back to space and this helps warm the local ocean surfaces further. If Greenland remains very cold and ice-covered the baroclinic zones of sharp atmospheric temperature and pressure- gradients would extend north-eastwards and northwards from the tip of southern Greenland, this would encourage more North Atlantic depressions to push deep into the Arctic. That process would, in addition bring warm southerly winds from the North Atlantic right up into the Arctic- further exacerbating regional warming. It is clear to see that if this feedback between more ice-free waters absorbing the Sun's heat in the summer, then attracting depressions into the area in winter bringing more warmth- really took off then the entire Arctic could become free of ice one summer, then remain free of ice as autumn and winter storms moved in over the ice-free areas with warm air from lower latitudes. Once the Arctic is ice-free and the surface waters stay above the freezing-point of ocean water year-round (-1.8C) the ice-free ocean would release a large amount of warmth into the low atmosphere. This would lower surface pressures but would also have a smaller warming influence on the high atmosphere over the Arctic. The main influence of the lowest 3,000 metres of the atmosphere being some 10C warmer in Autumn and 15 to 20C warmer in Winter would be a drop in average surface-pressures over the central Arctic by 15 millibars in Autumn and 20 to 25 millibars in Winter- that fact alone combined with the stronger atmospheric temperature gradient between much warmer conditions in the low troposphere and still very-cold air in the upper-atmosphere would be strongly conducive to storm activity in Autumn and Winter. The article referred to here lends support to this thesis (https://journals.ametsoc.org/view/journals/clim/31/19/jcli-d-18-0109.1.xml). In Summer, an ice-free Arctic would be little warmer than the part-thawed pack-ice there today, unless sea-surface temperatures could get well above freezing-point: It is thus likely that the Central Arctic would not experience more summer storms in a warmer world, but hotter conditions on the continents surrounding the Arctic in a warmer would still increase the crucial baroclinic atmospheric temperature contrasts to increase cyclogenesis at the margins of the Arctic- with worrying implications for coastal erosion along the Arctic coast-lines of Canada, Alaska and Russia. This still implies, for the purposes of discussing the wider implications for mid-latitude weather-conditions, a general northwards shift in storm- tracks. We now look at what the implications of increased temperatures and storminess in the ice-free Arctic Ocean mean for regions well to the south of the Arctic Circle. There is a school of thought that believes an ice-free Arctic ushers in wetter conditions with stronger winds in temperate latitudes, with severe winter cold spells becoming a thing of the past (not least because the World would be 3C warmer and middle-latitudes are not far from the unfrozen Arctic Ocean region that will be 20C or more warmer in winter). Certainly this means that any northerly winds coming from the Arctic interior will not bring severe cold to Britain during the winter months, but this does not rule out cold air coming from the east even if sea-surface temperatures around Britain are 4C warmer at the start of the winter. And there is no guarantee that that will be so because if the North Atlantic Drift weakens in response to weaker Westerlies sea surface temperatures around the UK may not be much warmer than today. The main influence of an ice-free Arctic Ocean, at least in Autumn and Winter will, from the above, be to steer the deep depressions (that normally push north-east from Iceland to north of Norway in Autumn and Winter nowadays) much more northwards along the East Greenland Coast and into the Arctic interior. Furthermore a much warmer Arctic in Winter would even ensure that the upper-atmosphere warmed a little (as cyclonic cloudy convection transfers heat into the upper-air)- increasing the 500 mb heights by 200 metres or more. That process alone would help decrease the strength of the Circumpolar Vortex by 10% or more, not least over the North Atlantic west of the UK. On the other side of the ledger, if the North Atlantic is 4C warmer in early winter that almost doubles the latent heat available to fuel deep depressions and could help tighten and strengthen the Circumpolar Vortex twice as much as the reduced Circumpolar Vortex might weaken it. That is particularly possible if Greenland is still ice-covered and Greenland/ north-east Canada still get very cold in winter, the sharp baroclinic temperature gradients in the atmosphere between Greenland/ NE Canada and a warmer North Atlantic would be a very potent source of cyclogenesis- but the question then becomes where do the depressions go, i.e. eastwards or northwards up the East Greenland Coast into the ice-free Arctic Ocean. If the depressions that normally headed just north of Norway in the past travel up the East Greenland Coast towards the North Pole in a warmer world that has very profound implications for the climate of western Europe (including the UK). Continued below.

With the Arctic sea ice extent by some measures reaching close to or event setting record lows today and area doing the same, it feels like it's about time the melt season thread got underway for 2019. There's been a phenomenal crash in the past week with the extent moving from 9th to 1st lowest position. In the GEFS mean 850 hPa and 500 hPA GPH anomaly plots for the next 5 days averaged, we can still see a large and strong footprint from the events that brought this crash about: There's essentially a 'warm Arctic, cold continents' (WACC) event going on. The impact on ice from this has been mostly via the unusual wind patterns moving unusually thin, fragile ice around, as opposed to melting it directly. It's still too cold near and at the surface for the most part even with such large anomalies aloft. The pattern shows strong persistence during the next 10 days or so. Ice declines may continue at above normal rates during this time, which could take 2019 well below any previously observed years, depending on the surface wind patterns and how much more ice is still in a position from which it may be driven into a melting environment. The pattern also served to decelerate the mid-latitude westerlies faster than usual. Once the displaced from Arctic cold air disperses or warms out, it's possible that this will facilitate an unusually rapid warm-up in regions without snow cover. Meanwhile, late snow gains across the likes of Scandinavia and E. Canada may manage to restrain the rate of advance of heat onto the Arctic, depending on how much the weather patterns de-amplify as the WAAC event subsides. I'm concerned that they may not do so very much given the El Nino event currently underway. That aside, this big loss of sea ice cover opens the door to the open water feedbacks that, before this event came into view, I had been wondering if would be negated for this melting season. Will anomalous atmospheric moisture content yet again (as was particularly evident each season 2016-2018) bring about more cloud and LP formation than usual to diminish the solar-driven melt April through July? Science really is built on questions! p.s. If for whatever reason this new topic is to be deleted, may I please request that this leading post is placed into the topic being used instead, TIA.

Poll number 4 of the summer. The average guess from the last poll was 3.54 million, up from 3.03 million in May, but with a lot less votes. After a slow melt in June, most extent and area measures are mixed, with 2016 somewhere between lowest and 3rd lowest on record. With volume, 2012 now has a clear lead, while 2016 now sits in 3rd, quite close to 2010, 2011 and 2013. With the weather looking highly favourable for melt over the next 10 days, lowest on record is still very much a possibility. Here are the daily minima since 2000, and the 80s and 90s averages. 80s 6.963 90s 6.423 2000 5.943 2001 6.567 2002 5.625 2003 5.969 2004 5.770 2005 5.314 2006 5.746 2007 4.147 2008 4.548 2009 5.047 2010 4.590 2011 4.333 2012 3.340 2013 5.040 2014 4.988 2015 4.341 As always, voting is set to private.

This is the 3rd sea ice minimum poll of the summer. The previous poll, posted on May 5th, had an average of 3.03 million km2 after 21 votes, while the April poll average 3.48 million from 16 votes. At the moment, we are still lowest on record by about half a million km2 going by most area and extent calculations, and lowest or 2nd lowest by volume. The sensor calibration is underway at the NSIDC and we should hopefully have the full official extent data back again soon. For now, we are going by the uncalibrated data provided by Wipneus. Here are the daily minima since 2000, and the 80s and 90s averages. 80s 6.963 90s 6.423 2000 5.943 2001 6.567 2002 5.625 2003 5.969 2004 5.770 2005 5.314 2006 5.746 2007 4.147 2008 4.548 2009 5.047 2010 4.590 2011 4.333 2012 3.340 2013 5.040 2014 4.988 2015 4.341 As always, voting is set to private.

This is the 2nd sea ice minimum poll of the summer. The previous poll, posted on April 5th, had an average of 3.48 million km2 after 16 votes. At the moment, we appear to still be lowest on record going by most area and extent calculations, and lowest or 2nd lowest by volume. Unfortunately, there was an issue with on the sensors used for calculating the NSIDC extent values used here, so we may not have NSIDC extent data for a few months. Here are the daily minima since 2000, and the 80s and 90s averages. 80s 6.963 90s 6.423 2000 5.943 2001 6.567 2002 5.625 2003 5.969 2004 5.770 2005 5.314 2006 5.746 2007 4.147 2008 4.548 2009 5.047 2010 4.590 2011 4.333 2012 3.340 2013 5.040 2014 4.988 2015 4.341 As always, voting is set to private.

We've just passed the maximum for the year, which, for the 2nd consecutive year, set a new record low. Current sea ice extent is the lowest on record, sea ice area is lowest on record and volume (according to PIOMAS) is the 2nd lowest on record after 2011. Here are the daily minima since 2000, and the 80s and 90s averages. 80s 6.963 90s 6.423 2000 5.943 2001 6.567 2002 5.625 2003 5.969 2004 5.770 2005 5.314 2006 5.746 2007 4.147 2008 4.548 2009 5.047 2010 4.590 2011 4.333 2012 3.340 2013 5.040 2014 4.988 2015 4.341 Votes are set to private and the we'll use the daily NSIDC data to determine the minimum. I'll update this a few times during the melt season.

I am enrolled at UNIS,Svalbard, studying Arctic glaciers till September. I am hoping to keep this blog updated with details of what I am up to and pictures. So far I am limited to Longyearbyen, having not received gun training, but next week will start with fieldwork. The weather has so far been sunny, and rather warm, reaching a high of 15c yesterday. The constant light is taking some getting use too! I'll be visiting a local glacier on Thursday, where I hope to update!

Seeing as nobody has started this topic... The melt season is here, generally lasting from March/April to September each year. After previous slight improvements in the minima in both 2013 and 2014 after the record low of 2012, many AGW "sceptics" see this as a sign of an Arctic sea ice recovery, while others see it as short term variation on a long term trend. Most extent and area measures have this years max as the lowest on record, while volume sits about 6th lowest and highest since 2010. So, how will this season pan out? A continued reversion to the mean or return to the long term downward trend?

Now that we're entering the full swing of the melt season, I thought it would be time for the first sea ice minimum poll of 2015. (Most ice info used here is based on the daily NSIDC daily sea ice extent data, unless otherwise stated). We've just come out of a very mild, though not exceptionally so, winter which saw the lowest sea ice maximum on record by most area and extent measures. 925hPa temps north of 70N ......... ............. .............. Maximum Sea Ice Extent The early part of the melt season has seen temperatures well above average across most of the Arctic, with sea ice extent generally in the bottom 3 on record, with the daily value of 12,531,000km2 being the 2nd lowest for May 16th (most recent). On the other hand, sea ice volume has continued to slowly grow from the minimum in 2012, with April 2015 the 7th smallest volume on record. There is a long way to go this melt season, but the forecast for the near term shows things warming up across much of the Arctic with temperatures climbing well above freezing, especially across the Pacific side, around the Beaufort/Chukchi regions, so a good chance of an accelerated melt period over the next 7 days. After that, who knows? (Votes are set to private, for anyone concerned about that)

The sea ice growth appears to be accelerating now, with NSIDC extent up over 300k on the minimum. including an increase of almost 60k yesterday, while the 5 day trailing average is up 165k on the minimum and 36k up on yesterday. Below is the extent increase (with the 5 day trailing average), between the minimum and September 30th for each year. The same, but for the minimum to October 31st each year is below it. Extent increases over the last week have been well above recent and long term averages, but temperatures look like warming up relative to average across much of the Arctic during the weekend and early next week, so closer to average sea ice coverage increases may occur next week.

It seems that we've likely passed the maximum this year going by most sea ice spatial coverage measures (area/extent). So with the refreeze over, it's time to start looking toward the melt season. The two polls above are based on the NSIDC data, with the first being the daily minimum, and the second being the September mean. Voting is set to private. I might create a new poll every month or so to see how opinions change during the inevitable ups and downs of the melt season. Going by the NSIDC extent data the daily maximum extent this year looks like it was 14,960,300km2 on the 20th, making it the 5th lowest maximum on record (since 1979), with the monthly average likely to be the 4th or 5th lowest. The volume according to PIOMAS was the 3rd lowest on record at the end of February. While this winter looks as though it was around the 2nd mildest on record (though changing the latitude bands may give slightly different values) Here are the daily minima from the past 10 years, with the monthly average in brackets. 2004: 5,776,080km2(5,989,560) 2005: 5,318,320km2(5,510,020) 2006: 5,748,770km2(5,868,890) 2007: 4,166,740km2(4,280,470) 2008: 4,554,690km2(4,695,040) 2009: 5,054,880km2(5,269,370) 2010: 4,599,180km2(4,872,050) 2011: 4,330,280km2(4,568,180) 2012: 3,369,730km2(3,580,150) 2013: 5,079,390km2(5,235,700)

Hi folks. It's time for the first ARCUS sea ice extent prediction poll of the summer. ARCUS basically gather the prediction for the mean September Arctic sea ice extent from different scientists, organisations and public contributions, and make short reports based on them. More information can be found here http://www.arcus.org/search/seaiceoutlook The poll is for the MEAN September sea ice extent, which is always slightly higher than the daily minimum. Below is a graph of the September mean since 1979 The values from the last 10 years are 2003: 6.15 millionkm2 2004: 6.05 millionkm2 2005: 5.57 millionkm2 2006: 5.92 millionkm2 2007: 4.3 millionkm2 2008: 4.73 millionkm2 2009: 5.39 millionkm2 2010: 4.93 millionkm2 2011: 4.63 millionkm2 2012: 3.61 millionkm2 Monthly data is here ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Sep/N_09_area.txt The current extent is at about 12.25 millionkm2. This is 11th lowest on record and almost the same as last year. The latest volume estimate from the PIOMAS model has us on lowest on record (end of April). The results of the prediction polls will be compared to the NSIDC data The results of this poll will be submitted on the evening of JUNE 7th, so any votes made after that time will not count.