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John Christensen
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NAO and high pressure across Scandinavia: Fascinating: It seems from the forecast http://globalweatherlogistics.com/seaiceforecasting/gfs.850mb.height.vort.arctic.html that the high across Scandinavia does not make it to the Arctic in time to cut off the low north of Iceland, which means this low will enter the Arctic and become another cyclone. This is what the NAO forecast is showing as the NAO turns sharply negative for a short period: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/new.nao_index_ensm.html Also when you see the bulging jet stream, you see how we continue to be bordering a negative NAO situation, with a north-bound jet stream in the Norwegian Sea: http://www.wunderground.com/global/Region/EU/2xJetStream.html This bulging jet stream has been with us for a few months, and while we have just entered October, and the Siberian cold is not strong yet, the question will be if the high across the Central Siberian Plateau will arrive early and strongly enough to push west in which case the jet stream is likely to keep bulging and we could easily have a winter with primarily NAO- and reduced sea ice buildup. I have no idea, if the bulging of the jet stream caused by the Siberian blocking high is a "true" NAO-, or if the blocking high just creates a situation, which resembles NAO-. However, the consequences would probably be the same: North-bound jet stream in the Norwegian Sea, enhanced snow cover in the Arctic region, but reduced ice volume increase. NH Snow cover and NAO: If NAO- really transports extra moisture into the Arctic region, then there should be a positive correlation between NAO- and NH snow cover. While I did not perform any quantitative analysis, it is interesting that for the month of December, the three years with highest NH snow cover are: 1. 2012 2. 2010 3. 2009 http://www.ncdc.noaa.gov/snow-and-ice/extent/snow-cover/nhland/12 If I had done more analysis, I would have had challenges: In the 60's - 80's, it seems like strong negative NAO during fall months, did not result in extra snow cover. What does that mean? My uneducated guess is that the increase in ocean heat energy in the past 30 years has caused NAO- to transport much more moisture and energy into the Arctic than happened with a similar NAO- fourty years ago. Therefore, AGW may be enhancing the impact of a natural phenomena such as the NAO..
Hi mark, There is a lot of speculation around what impacts the NAO. From what I have seen, it seems most likely that events in the tropics are shifting the ridges across the Atlantic, thereby impacting the NAO. I am not arguing that the NAO would be the sole contributor for any event, and for extreme events such as e.g. the melts of 2007 and 2012, you need multiple factors to coincide, creating the perfect storm. However, when you look at monthly NAO values combined for June, July, August and rank the years, you get very prominent rankings for post-2007 years, even to some degree for 2014, while 2013 is near the bottom of the list: Year JJA 2012 -4.83 1958 -4.67 2011 -4.14 2008 -3.82 1993 -3.65 2009 -3.55 1998 -3.22 1980 -3.03 1954 -2.75 2014 -2.47 2010 -2.46 1957 -2.46 1962 -2.17 1987 -2.13 2007 -2.03 1956 -2.02 1963 -1.84 1974 -1.54 1950 -1.37 2000 -1.35 1977 -1.30 1960 -1.26 1968 -1.13 1952 -0.77 2001 -0.52 1951 -0.49 1966 -0.39 1969 -0.33 1997 -0.30 2004 -0.24 1982 -0.22 2005 -0.19 1991 -0.08 1985 -0.06 1981 -0.01 2003 -0.01 2006 0.01 1971 0.22 1986 0.25 1975 0.45 1988 0.57 1995 0.60 1999 0.61 1984 0.66 1989 0.71 1953 0.78 1978 0.88 1973 0.90 1965 1.06 1959 1.20 1992 1.21 1961 1.37 2002 1.38 1964 1.42 1990 1.48 1955 1.73 1970 1.75 2013 2.16 1996 2.25 1972 2.38 1976 2.40 1994 3.21 1967 3.25 1979 3.39 1983 3.79 Total NAO for JJA is: -20.73 with an average value of: -0.3189 Regarding the 2007 event: - From the monthly NAO values you see that Aug-Sep-Oct of 2006 had a combined NAO index of -5.59, the most extreme negative NAO index for any three consecutive months in the entire NAO record: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table - On CT Area data you notice that late fall/early winter of 2006 set a new negative area anomaly record of -1.5M KM^2, and that the CT area for the first week of February 2007 is still the lowest on the record: http://arctic.atmos.uiuc.edu/cryosphere/arctic.sea.ice.interactive.html So IMO 2007 happened because of extensive ice export via Fram during the summer of 2007 and unfavorable high pressure areas, but also because of the very low ice cover/late freeze during the winter of 2006/2007, where negative NAO was a factor in delaying/reducing the freeze.
Exactly jdallen.
Another trivia on negative NAO (NAO-): The longest period of NAO- since 1950 was Oct. 2009 - January 2011. I saw somewhere (failed to mark the page) that there was a negative correlation between NAO- and NH average temperature, which intuitively makes sense, since NAO- enhances the polar heat sink effect by increasing the transport of Atlantic moisture to the polar region. Interesting question: Could the predominance of NAO- since 2008 have assisted in the much discussed 'break' in global temperature increase? Just with the side-effect that Arctic sea ice is melting away under NAO- in the last few years, because it cannot withstand the increase in Atlantic moisture inflow as well as it could back in the 60's and 70's..
To put the anomaly of -2.53 into perspective, of 192 summer months (JJA) since 1950, we have had just six with a negative NAO anomaly above 2: July 1993: -3.18 June 1998: -2.72 June 2012: -2.53 July 1962: -2.47 Aug. 1980: -2.24 July 2009: -2.15 http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.current.ascii.table However, if you combine the NAO values for JJA, 2012 has the highest negative number..
See contrast in NAO index between 2012 and 2013 Month 2012 2013: J: 1.17 0.35 F: 0.42 -0.45 M: 1.27 -1.61 A: 0.47 0.69 M: -0.91 0.57 J: -2.53 0.52 J: -1.32 0.67 A: -0.98 0.97 S: -0.59 0.24 O: -2.06 -1.28 N: -0.58 0.90 D: 0.17 0.95
And then the Atlantic forecast for the next few days: http://globalweatherlogistics.com/seaiceforecasting/gfs.850mb.height.vort.arctic.html As you see, the high across central Europe will move up across Scandinavia and then merge into a high across the Arctic. You can see this also on the AO turning strongly negative (Same as high pressure across the Arctic): http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.shtml If the NAO had been negative right now, there should have been a ridge in the mid-Atlantic to assist pushing the low east of Greenland to the north, but it seems the lack of negative NAO will cause other factors to prevent this low from having any major impact on Arctic sea ice. And an interesting article on the melt of 2012 and NAO: http://thinkprogress.org/climate/2013/06/17/2169321/exceptional-2012-greenland-ice-melt-caused-by-jet-stream-changes-that-may-be-driven-by-global-warming/ From this article: "Professor Edward Hanna from the University of Sheffield’s Department of Geography explains: “The GrIS is a highly sensitive indicator of regional and global climate change, and has been undergoing rapid warming and mass loss during the last 5-20 years. Much attention has been given to the NASA announcement of record surface melting of the GrIS in mid-July 2012. This event was unprecedented in the satellite record of observations dating back to the 1970s and probably unlikely to have occurred previously for well over a century. “Our research found that a ‘heat dome’ of warm southerly winds over the ice sheet led to widespread surface melting. These jet stream changes over Greenland do not seem to be well captured in the latest Intergovernmental Panel on Climate Change (IPCC) computer model predictions of climate change, and this may indicate a deficiency in these models. According to our current understanding, the unusual atmospheric circulation and consequent warm conditions of summer 2012 do not appear to be climatically representative of future ‘average’ summers predicted later this century. “Taken together, our present results strongly suggest that the main forcing of the extreme GrIS surface melt in July 2012 was atmospheric, linked with changes in the summer North Atlantic Oscillation (NAO), Greenland Blocking Index (GBI, a high pressure system centred over Greenland) and polar jet stream which favoured southerly warm air advection along the western coast. “The next five-10 years will reveal whether or not 2012 was a rare event resulting from the natural variability of the NAO or part of an emerging pattern of new extreme high melt years. Because such atmospheric, and resulting GrIS surface climate, changes are not well projected by the current generation of global climate models, it is currently very hard to predict future changes in Greenland climate."
Hi mark, I think the point is that the atmospheric circulation is complex.. In my comments above, I have tried to simplify matters by focusing on the NAO, but as also explained, the NAO is just one typical blocking high in the NH out of few key ones: North-East Pacific/Rocky Mountains, Greenland, and the Central Siberian Plateau. Right now, the jet stream across the eastern North America is further to the North than usual, and moves south around Greenland: http://www.wunderground.com/global/Region/CN/2xJetStream.html? It then bulges towards the North and near Svalbard, after which it bulges to go south of the Siberian high: http://www.wunderground.com/global/Region/EU/2xJetStream.html Consequently, you have very cold air from this jet stream meeting warm waters south of Greenland: http://ocean.dmi.dk/satellite/index.uk.php Which in turn causes these strong lows to build up on the north side of the jet stream, where they are out of reach so to speak for the jet stream, and are free to move north, as you see happening right now: http://ocean.dmi.dk/arctic/weather/arcticweather.uk.php To interpret this situation, it seems that the high across the US Midwest is causing the jet stream to stay further north and therefore to create the jet stream bulge, which allows these strong lows to develop and move north in the Norwegian Sea rather than the typical setup, where the jet stream leaves Newfoundland and crosses the Atlantic more directly towards the British Islands and Northern Europe (which then carries the lows in a more East-bound direction).
Again on AO vs. NAO: One might ask; if the current cyclone is harmful to the ice, how could the high frequency of cyclones during the summer of 2013 be preserving the ice cover? Two reasons for this: 1) There are lows and then there are very destructive lows: Last summer we had the combination of positive AO (indicating prevalent Arctic low pressure), but also positive NAO, which means that stronger North Atlantic lows were steered east/north-east rather than moving straight north in the Atlantic. Consequently, the Arctic cyclones last summer did not contain a high amount of energy and further, as Neven included in the great entry on cyclones last year, the difference in temperature between warmed continents and cold Arctic Ocean in itself helped to sustain the cyclones, so that these were to a certain degree separated from strong inflow of ocean heat - at least from the Atlantic. 2) The timing: A cyclone in June or July will increase cloud cover, limitation sun radiation, which in that period happens 24 hours a day. Now by late September, the Arctic is cooling, so a cyclone would necessarily be driven by oceanic heat/moisture, which increases the temperature in the areas of the Arctic impacted by the central low pressure area.
Hi Ghoti Of Lod, Thank you for the interest! The 3 month running mean of the NAO has been used primarily to perform causal analysis of NAO impact during winter months, while there has been little focus on NAO during summer months. You see the impact of the current cyclone very clearly on the DMI graphs, such as in the latest image, where temperatures have increased significantly in the cyclone impacted area near the Pole: http://ocean.dmi.dk/arctic/weather/arcticweather.uk.php If strong westerlies (positive NAO) caused this North Atlantic low to travel further, before it reached the central Arctic Basin, then the low could have lost 15-20% of its energy, compared to a negative NAO situation, where the low could would have followed a more direct route to the Arctic Basin. I will check if DMI has done more analysis on this.
One more update on the Arctic low: DMI has a great graphic showing that as of yesterday the cyclone seems to have put the ice into significant motion with a current speed similar to what you see in ice-free waters (Select surface current and Arctic Sea): http://ocean.dmi.dk/anim/index.uk.php This seems to be possible, as the strongest winds of the cyclone follows the same area, where we saw what appeared to be an undercurrent of warm waters leaving the Laptev Sea in a counterclockwise movement towards the Pole and then south into Barents Sea between Svalbard and Franz Josef Lands from late July into September. No doubt that this movement of ice and mixing with top water layers will delay freeze in the area, helped by the temperature increase caused by the cyclone, as is clearly visible on the DMI 60N weather graphic. The next strong Atlantic fall cyclone is shaping up between Greenland and Iceland, and with NAO moving towards neutral state the cyclone may take a more direct path to the central Arctic Basin.
Sorry, let me retract my last comment: The jet stream apparently moved a bit south over the weekend, so that by Sunday it was crossing Norway rather than going around the Scandinavian peninsula on the north and then going south: http://www.wunderground.com/global/Region/EU/2xJetStream.html Due to the new position and probably the strong blocking high over Siberia, the jet stream had a less pronounced northern direction just east of the Scandinavian peninsula. The low therefore seemed to follow the road of least resistance moving straight North. This event has now played out with the center of the low placed between Franz Josef Lands and the Pole by Monday morning, European time: http://ocean.dmi.dk/arctic/weather/arcticweather.uk.php Regarding the question of the impact of NAO on Arctic sea ice, let me summarize from this event: - NAO index was medium strong and positive (1.5), increasing westerlies across Northern Atlantic - This caused the cyclone to move to Norway from its prior position just north of Iceland, which is an ENE direction - The cyclone then entered the Barents Sea, now in a NE direction - Finally, it got redirected going straight North, where it seems it will dump its final load of moisture across the central area of the ice pack - The positive NAO therefore did not prevent the low from entering the Arctic - but it significantly extended the distance for the low to reach the Arctic from Iceland, in which time the system is reduced from a heat/energy perspective
Last comment on the North Atlantic low, which has now become an Arctic low: What I did not spot a couple of days ago was the high developing over the CAA, which attracts the North Atlantic low, breaking it into two, where the majority of energy now moves straight North from the northern-most point of Norway and across Franz Josef Lands towards the Pole. A minor fraction will follow the jet stream moving south-east towards the Ural mountain range: http://ocean.dmi.dk/arctic/weather/arcticweather.uk.php You can see this play out on the CT forecast: http://globalweatherlogistics.com/seaiceforecasting/gfs.850mb.height.vort.arctic.html
For those who can read Norwegian, an update on this storm: http://www.yr.no/nyheter/1.11953411 As is stated there, they expect precipitation as rain and not snow, but in Northern parts of the country up to 140mm in two days, which is a lot.
On Atlantic moisture, NAO and the Arctic. As you see from DMI's 60N weather image there is currently a massive low covering nearly the entire Norwegian Sea, or about 5,000,000KM^2: http://ocean.dmi.dk/arctic/weather/arcticweather.uk.php Now, if the NAO had currently been strongly negative, this low would move straight North, bringing a tremendous amount of moisture into the center of the Arctic region, which would delay/slow down sea ice accumulation there. While the low is still at a distance, pressure gradients in the central Arctic are low, so the weather is relatively quiet, dominated by a much weaker low centered in the Laptev Sea (also not surprising given the open water there). The low pressure gradients have allowed surface temperatures on the DMI 60N image (above link) to move below -15C for the first time this season in a small area between the Pole and Beaufort. The NAO is right now positive, but not strongly: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao_index.html However, this should be sufficient in ensuring that the massive low moves North-East skirmishing the Norwegian mountain ranges, dumping loads of snow there/releasing heat, before the low probably enters the Barents Sea near the Russian North coast. The current jet stream then would push the low south due to a blocking high in Siberia, but IMO it might as well cut its own path towards Kara and then Laptev causing still massive precipitation, but with a considerably colder core temperature when reaching central Arctic areas than we would have seen under strongly negative NAO. It will be interesting to watch how this plays out the next two-three days, as it should be a classic example of how the NAO steers the North-Atlantic lows.
Hi mark, Being on the overall skeptical side of matters myself and recognizing the way scientific paradigms limit the perspectives even of scientists, as well as being ever hopeful/optimistic on behalf of the resilience of Arctic sea ice, I need to agree with others here that it is of little value to point to the state of the climate a thousand years ago, or otherwise at the high level to question what is happening. This blog is focused on Arctic Sea Ice, and being just this, it is extremely valuable from my perspective, to try and understand the nature and weight of the different factors impacting Arctic sea ice. This will increase our knowledge and improve estimations of what will happen in the next 5, 10 and 50 years, both to the ice and the World we live in. Being further along on the skeptical line, you should have a close look at PIOMAS data, look at the graphs, download the daily volume readings, check interyear changes, etc., and you will realize that it does not matter what weather we had a thousand years ago - or 6,000 years ago where we had an increased and significant warm spell. The Arctic sea ice is disappearing, rather rapidly..
Hi Colorado Bob, Thank you for your comment. And yes; I am sure he is very capable of measuring and do not doubt the numbers. We know volume is decreasing faster than area or extent, which affirms his measurements. It is the generalization and conclusion he makes, which does not appear to be scientifically based - unless he is just stating that the 0.8 meters of ice in his area of measurement could melt away in one to two years, which is certainly possible, agreed. If he did refer to the Arctic as a whole and state it is possible for the Arctic sea ice to melt away in less than two years, then he needs to substantiate the argument, as this is an extreme standpoint, to say the least.
Yes, I fully agree with you Neven.
Sorry, I should have simplified the metric: One gigaton equals 1KM^3 of water, ie. about 1.1KM^3 of ice in a compressed state. The 12 gigaton of precipitation therefore corresponds to about 13KM^3 added to the ice sheet, being 2% of the 530KM^3 mean growth for the entire freezing season (1990-2011 reference), and this low is likely to provide further accumulation as it moves North today and tomorrow.
On Atlantic lows: A significant Atlantic low moving towards the Arctic dumped a very significant amount of precipitation on Greenland yesterday, adding an impressive 12 Gigaton of snow (Corresponding to 12,000,000,000,000 liters of water in one day): http://polarportal.dk/en/groenlands-indlandsis/nbsp/isens-overflade/ As you see on the "Accumulated" tab, the Surface Mass Balance has been positive since September 1st due to the above-normal level of Atlantic lows moving North along the east coast of Greenland. The same lows, which have extended the Arctic sea ice melting for another week this year.
Colorado Bob, In all fairness, the statement from Professor Wadhams seems to be more political than scientific, leading up to the climate discussions taking place tomorrow. PIOMAS has average sea ice thickness at around 1.40M, so it was not really "the Arctic sea ice" on average that was 0.8M, but probably the average in the area surveyed this summer by the Oden (which was near Laptev and ESS and not on the CAA side of the Arctic). To note that Arctic sea ice in general could melt out in one to two warm summers, making this seem like a probable scenario, does not have scientific validity, as the chance of this happening must be very insignificant. Professor Mark Serreze was included in the same article: "Professor Mark Serreze, director of NSIDC – who will also speak at the Royal Society – agreed with Professor Wadhams that the ice cap was disappearing and added that it would eventually shrink below one million square kilometres (386,000 square miles), therefore reaching the definition of an "ice-free Arctic". He did, however, add that he believed that this would take longer that Professor Wadhams predicted."
Thanks Chris! I would be interested in knowing what the DMI ice team thinks of the possible impact of a strong NAO index, so may try to reach to them.
Toggle Commented Sep 16, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Thank you for another great update Neven! - and your perseverance in spite of all the distraction above. I just had one note to your comment on the DMI 80N: "And even though temps are now dropping on the DMI 80N temperature graph, we're not yet seeing the upward spikes that usually indicate that the Arctic Ocean is massively releasing its heat so that it can refreeze" You are correct, but that is a good thing (from the ice/polar bear perspective): We are not seeing the spikes yet because the ice condition near the Pole has slightly improved since last year this time, and improved a lot since two years ago at this time. The temperature could drop just a bit more, before the spikes start occurring - which they certainly will given the immense Laptev Bite this year.
Hi Chris, It is correct that the NAO is a subset of the AO - the NAO is simply the Atlantic component of the AO. I am interested in the NAO, since this oscillation shows in one mode (negative) an increase in Atlantic moisture moving north into the Arctic region, while in the opposite mode (positive) less moisture moving north from the Atlantic. It is interesting to analyze if this transport of Atlantic moisture impacts the Arctic sea ice and SST during summer months. Since I specifically am interested in analyzing a hypothesis on the transport of Atlantic moisture and the NAO is just a subcomponent of the overall AO, which includes the entire Northern Hemisphere, why on Earth would it have relevance to use AO numbers and not NAO numbers for the analysis of Atlantic moisture transport???
Toggle Commented Sep 13, 2014 on PIOMAS September 2014 at Arctic Sea Ice
Michigan March 2014 was fifth coldest on record and not far from record cold. You find the four most severe Arctic outbreaks during the month of March in Michigan in the period of 1899-1960, where severe Arctic outbreaks in general were much more frequent. The argument from Dr. Francis as has previously been discussed, seems still to be theoretical and not yet reflected in actual climate data, but if you believe so please show this.
Toggle Commented Sep 12, 2014 on PIOMAS September 2014 at Arctic Sea Ice