This is John Christensen's Typepad Profile.
Join Typepad and start following John Christensen's activity
Join Now!
Already a member? Sign In
John Christensen
Recent Activity
@wayne, Having following the entire process closely the past 4-5 years, I do not see in comparision between this year and last year at this date that an imminent crash is likely. Look at CT for 7/24 for '14 and '13: You see that the Beaufort was equally disintegrated last year, while Chuckchi, ESS, and the triangle between Laptev, the Pole and Franz Josef Lands all was more disintegrated a year ago. Yes, it was saved by the bell last year, which a significant low spreading the remaining ice, and low temps preventing that huge crash, which otherwise seemed likely. A reason why the crash did not happen, was that SST was quite low, relatively. Right now we have about 400K km^2 more ice area than 12 months ago, and with similar temps (dmi 80N), I would suspect most of the difference to be due to an increase in compactness of the ice, although the disintegrated ice pack last year probably also supported relatively few melt ponds - as direct consequence of the disintegration. The forecast has a larger and stronger cyclone moving to near the Pole this week, which will keep temps down, but should cause additional disintegration of ice at border areas, so agree that it will be interesting to watch to what degree the near-coast warm waters will mix with ice and cause rapid melting. The higher compactness of ice centrally in the CAB this year, however, should cause less mixing with top-water, so reduced melting in the CAB. Let's see..
Based on weather in the past couple of weeks, low temps/cloud cover plus outlook for AO and NAO, I would no longer be surprised, if 2014 Sept extent and area will be in tight competition with 2013. I find it unlikely that Sept extent should be less than 5.0M KM^2 at this point.
You are right Chuck - thanks for the correction. I normally look at the standardized 3-month mean value, which is not the same: I should have double-checked as it is also clear on the DMI 60N weather view that we have had a few broad highs in the past 4-5 weeks. Even on the AO site, there seems to be disagreement, whether it will stay near neutral (e.g. on the 14 day forecast) or will turn considerably more negative as indicated in the top chart. Of the AO and NAO, I would think the NAO often has stronger impact on ice conditions, but will be interest to see, how the summer unfolds.
Toggle Commented Jul 7, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
@Chris, Agreed, that 'ice state' has changed, and more specifically that this would be the age of the ice: The turnover of the ice pack has increased post 2007, so that a higher percentage of the ice is created and will melt again in each season - FYI with higher salinity. The higher volume losses post 2007 are therefore to some degree (while of course not fully) mirrored by higher volume gains in October, November and December for these last six years compared to the 80's and the 90's.
Toggle Commented Jul 6, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Just to moderate the comment above: It is probably impossible to determine any ultimate 'cause' of weather events in the 1-3 months range, as also the AO and NAO indices are influenced by the placement of ridges, blocking highs, SST in both the Pacific and Atlantic, etc., but at least indicators like the 80N temp, existence of melt ponds, cloud cover, etc. will have a strong correlation from the phase of AO and NAO..
Toggle Commented Jul 6, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Causes and Effects.. From obervations this season, it seems to me that many commenters are looking at the effects of underlying causes rather than the causes in order to explain current ice volume, cover and to predict Sept. minimum. It would seem reasonable to consider 'Sea Current' and 'Movement of Airmasses' as main causes in determining what happens during a specific melt season - i.e. irrespective of longterm downward trend: Sea Current: We know that currents such as the Irminger Current show some pattern in periodic changes both in strength and temperature of the current - and that there is a link between this current and the AMO, which was negative from early 1960's until the mid-90's, and has been positive since: I would argue that the AMO in the positive phase in general delays autumn freeze and increases bottom melt, allthough I have not found many articles studying the AMO. Movement of Air Masses: Movement of air masses; Arctic air decending into mid-latitude regions, warm/humid air entering the Arctic, etc. is to a very considerable degree governed by the AO and the NAO. If you look at the NAO for main summer months since 2000 you have: Negative NAO (Atlantic air moving north into the Arctic): 2000, 2001, 2005, 2007, 2008, 2009, 2010, 2011 and 2012 Neutral NAO: 2003, 2004, 2006, (and 2014) Positive NAO (Atlantic air moving primarily east into Northwestern Europe): 2002, 2013 It is no wonder that the type of summer caused by negative NAO has become our expectation.. Combining this with the AO, you will see that e.g. 2007, 2008, and 2009 also had AO in the negative phase, which combined Arctic high pressure with inflow of warm Atlantic air masses - not good for sea ice. Then take 2013 and 2014 in contrast: 2013: Positive AO and positive NAO 2014: Positive AO (leaning towards neutral) and neutral NAO Given these oscillation indices you can derive the rest for 2013: Massive cloud cover, low temps and few melt ponds. For 2014: Mixed/good cloud cover, low temps, few melt ponds. Especially, it is noticable how the temps are low between Svalbard, Franz Josef Land and Novaya Zemlya, due to reduced inflow of warmer Atlantic air masses, even keeping the CT Arctic Bassin SIA above normal. We are nearly halfway through the main summer months, and with both the AO and NAO trending for near neutral conditions, I would expect temps to stay near or just below average, no major high to develop and therefore that the ice will do fairly well in the coming weeks, especially as the central pack is in a better shape than a year ago from the northern coast of Franz Josef Land to the northern edge of the Beaufort Sea. And 'fairly well' IMHO would be around 2009 lines and therefore below 2013.
Toggle Commented Jul 6, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Thank you for the great update - and for the comment Neven! And yes, this is an interesting year. It seems of course that every year is actually interesting, just each time for different reasons. Of the main factors contributing to heavy Arctic ice loss (geographic distribution and strength of highs and lows, melt ponds, and SST), 2013 had the ideal combination for low melt: - Central Arctic lows keeping temps down/reduce melt ponds and ice transport reduced, as well as positive NAO for summer months, reducing heat transport from the Atlantic Ocean. It is interesting to note that the last summer with even sligthly positive NAO during summer months was back in 2006: 2010 and 2012 had very strong negative NAO during summer, evidently causing massive heat being transported to both the Arctic region as well as much of Greenland. 2007 in contrast had only sligthly negative NAO during summer, but then had this combined with massive Arctic highs and strong ice transport. This year seems to be a mixed bag of lows and highs, but with little transport. NAO is nearly neutral, evidently reducing northbound heat transfer, which to me seems to be the factor, which so far makes 2014 fare a bit better than anticipated (i.e. keeping temps down and limiting melt ponds). With the strengthened central pack in the CAB compared to a year ago, and with peripheral seas nearly wiped out by now, I would not be surprised if PIOMAS numbers would show June 2014 volume loss to be less than for June 2013, but let's see..
Toggle Commented Jun 30, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Just noting that SH positive anomaly SIA on CT has passed 2M km^2 for the first time since record keeping began in 1979, and Global SIA right now is the highest since 1996 as a consequence of this.
Rob, Great analysis and very interesting that late spring NH snow cover can explain Sept minimum to that degree! Looking at the data for 2010, my take is that this year saw a significant deconsolidation of the Arctic ice pack in the sense that a lot of MYI was lost and significant fracturing took place, allowing the remaining, broken ice to spread better, bumping up the ice area and more significantly the ice extent. 2010 also had significant positive NAO during summer months, bringing warm moisture to the Arctic, assisting in fracturing the ice. 2007 was the opposite situation, where the MYI held the central pack well together and consolidated, but with significant melting taking place from open waters at the edge of the pack. For 2013, your analysis predicted a very high Sept minimum, but even assisted by a consistent negative NAO during the summer months and ice-preserving weather conditions overall, the Sept minimum fell below the prediction, probably simply due to the very thin, fragile ice cover.
Toggle Commented Jun 11, 2014 on PIOMAS June 2014 at Arctic Sea Ice
Area (CT) and extent (ROOS) predictions from my perspective are based on current ice conditions (thickness, concentration), which are average OK, weather forecast, which is positive for ice conservation due to weak, broad Arctic lows in the coming week, 80N DMI temp, which is low also due to weather, and the NAO forecast, which is negative and could lead to more Atlantic moisture moving North in the coming two weeks: - Area minimum: 3.4 +/- 0.5 M KM^2 - Extent minimum: 5.2 +/- 0.7 M KM^2
Toggle Commented Jun 11, 2014 on PIOMAS June 2014 at Arctic Sea Ice
Shanks for sharing Neven - great analysis by NSIDC! @George, Agreed, it will be very interesting to follow NAO, as I had never considered the correlation between negative NAO and Greenland (and Arctic?) ice melt to be this strong. Current outlook is undecided - as it often is..:
Toggle Commented May 25, 2014 on Greenland 2013 in review at Arctic Sea Ice
Agreed Neven, and I guess only time can tell. Regarding Arctic weather/wind and temp anomalies, DMI just launched a new page which is updated daily: For Greenland, DMI has also posted an interested view of 'albedo-anomaly' compared to 2000-2009 average:
Toggle Commented May 20, 2014 on ASI 2014 update 1: melt pond May at Arctic Sea Ice
Thank you for the first great ASI 2014 melt update Neven - what a show we have ahead of us! I agree with your assessment of melt ponds as a prime villain, but would add also early melt season ice compaction as a key factor, since it exposes sea water to the atmosphere (and sun radiation) early in the season and near the max level of inbound sun radiation. The cyclone of late May last year prevented both: Low temps kept melt ponds at a minimum and the spreading of cracked sea ice kept ice concentration at relatively high percentages until late June. And to the melt ponds: You have SIA this year faring slightly better than SIE, which could be an indication of low amount of melt ponds, as SIA models tend to show melt ponds as open water underestimating the ice area. This is positive for the ice, but the low concentrations near shore in Laptev, ESS, Chuckchi, and Beaufort do not bode well for the season, unless a solid cyclone gets in place to disperse the remaining ice IMO.
Toggle Commented May 19, 2014 on ASI 2014 update 1: melt pond May at Arctic Sea Ice
Regarding the 'second bump' in volume by end of April, there could possibly have been new ice build-up in the western part of Hudson Bay, as winds had compacted ice near the eastern coast and temps remained low. Also in Laptev, temps have come down again after ice being moved north, so some new ice should have formed. Just not sure this would justify the bump..
Toggle Commented May 9, 2014 on PIOMAS May 2014 at Arctic Sea Ice
Sorry for deviating from topic, but with the impressive development in Antarctic SIA, it would be very interesting to see sea ice volume numbers from down under, but I assume this data is not being tracked?
Toggle Commented May 8, 2014 on 2013/2014 Winter Analysis at Arctic Sea Ice
Yes, thanks for a quick update on PIOMAS Neven! PIOMAS average thickness: The average thickness is calculated for the PIOMAS domain by only including locations where ice is thicker than .15 m (i.e. by extent) Since ice area has declined less than ice extent in April, the average thickness has increased more with the PIOMAS calculation rather than with your calculation using the area numbers.
Toggle Commented May 8, 2014 on PIOMAS May 2014 at Arctic Sea Ice
@R. Gates, You should check Neven's entry from last year on summer cyclone behavior: This cyclone does not have similar behavior to a tropic cyclone (other than the anti-clockwise rotation), since compared to surrounding air masses it does not contain warm humid rising air at the center. As it simply circulates with fairly stable vertical air masses at the center, it will break the ice where the ice is weak enough to be broken and the breaking of the ice would assist in dispersing the ice. At the center of the cyclone, the ice will break down faster with stronger winds/lower pressure, as the mixing with top water layers increase. Overall, however, as we saw last year the cyclonic pattern tends to conserve the ice, apparently due a mix of factors: - Blocking of sun radiation/cloud cover - Sligthly lower temperatures (cyclone isolates Arctic air mass from surrounding warmer air masses) - Increased albedo, as consequence of ice being dispersed (this is probably more speculative, but it seemed from last year that even the thin ice cover had a significant impact in preventing top water layers from warming. And as has been shown elsewhere, heated top water is excellent for melting nearby ice) Forecasts have the cyclone staying more or less in place for the next week, so will be interesting to follow.
Toggle Commented May 7, 2014 on 2013/2014 Winter Analysis at Arctic Sea Ice
Thank you for a great analysis of development during the winter months, Neven. I agree with your conclusions, and that we should expect minimum area and extent to be in the range between 2012 and 2013, i.e. be close to 2010 or 2011. DMI has an extent graph (based on OSISAF), which is interesting, as it seems to show the importance of the direction of the extent in early-mid May: Extent by late April apparently having little impact on summer extent (see 2012), while it does become increasingly important to retain extent by mid-May, as it impedes sun radiation in reaching waters of the Arctic seas (since by mid-May edges of the Arctic Basin are starting to open up). From the DMI graph we are a bit low on extent this year, and with warm air being pulled in across the Beaufort, in addition to ice being pushed offshore in Laptev), it seems weather will need to be even more favorable this year to have a repeat of last years reduced melting, allthough ice quality has improved somewhat. For PIOMAS, I would expect we have caught up with 2013 again since we last year had more ice in Okhotsk and Bering, which has dropped fast in prior weeks, and also the 80N temperature in the past month has been quite similar to 2013. The forecast shows a cyclone entering the basin from Bering/Beaufort in the next couple of days, pulling air north from the CAA and Greenland, and it seems a solid high is also getting in place on the Central Siberian Plateau (CSP), pushing the jet stream north across Laptev and ESS - just weather or early indicator of repeated pattern from last year?
Toggle Commented May 5, 2014 on 2013/2014 Winter Analysis at Arctic Sea Ice
Hi George, Yes, the bridge is still in place. You can check this on the DMI ice temp chart: Or one a DMI satellite image (ASAR has a nice view):
Toggle Commented Apr 15, 2014 on PIOMAS April 2014 at Arctic Sea Ice
Great to see that the writer is looking for advice from an 'expert community' for the upcoming fiction piece. One time this clearly did not happen, was when the significant Hollywood production G.I. Joe - Rice of the Cobra missed the point that ice floats.. What makes this scary, is that someone asked if it could be true that ice would sink when the pack is blown to pieces, and the highest rated answer is that ice floats on salt water, but sinks in fresh water.. ;-) You cannot make this up..
Toggle Commented Apr 14, 2014 on Research for a novel at Arctic Sea Ice
Link to the DMI ice drift map, which clearly shows the continued northernly flow in Laptev: This would be a significant difference from the setup a year ago, where the ice was stable here, while quite similar to the situation two years ago leading to unprecedented ice melt during summer months. The early opening of the waters in Laptev should have a negative impact on the ice both due to early access of sun radiation to the water surface as well as reducing chances of creating the cyclonic environment we witnessed last year.
Toggle Commented Apr 10, 2014 on PIOMAS April 2014 at Arctic Sea Ice
Sorry Neven, for deviating from the topic here - I will make this just one comment. Hi Chris, You stated " I've said before I don't get why some follow a system in a death spiral and keep rooting for ice survival." My counter-argument is that it's not about the Arctic Sea Ice, but about the global eco-system that we have adapted to. Consciousness about global warming and sea ice is not global; people in Syria, Haiti, Central Africa, Africa's Horn, and many other places have accute challenges of poverty, disease, and threats to their lives, which makes global warming a remote intangible concept of low priority. I don't believe any population will remain in their huts, houses or caves made of dirt or straw at the risk of malnutrition, disease and exploitation from stronger powers in their area. They will eventually be educated and will want basic levels of social and economic freedom and stability. It took the Western world about 200 years to reach a point where we start seeing energy consumption levels go down in some countries, as well as increase in transition to renewable energy sources. See example of Denmark: It will take another 100-150 years to get the rest of the world to this point (probably quite optimistic), and this would even require many of the remaining countries to leap frog from subsistence farming to a modern society based on economic exchanges. So yes, I am rooting for the ice, not to be naive about what is happening in front of us, but because I do not see how the entire world can transition to a different mode of energy consumption within years or a few decades given the social and economic situation of nearly a billion people: From Worldhunger: The United Nations Food and Agriculture Organization estimates that nearly 870 million people of the 7.1 billion people in the world, or one in eight, were suffering from chronic undernourishment in 2010-2012. Almost all the hungry people, 852 million, live in developing countries, representing 15 percent of the population of developing counties. There are 16 million people undernourished in developed countries (FAO 2012). The number of undernourished people decreased nearly 30 percent in Asia and the Pacific, from 739 million to 563 million, largely due to socio-economic progress in many countries in the region. The prevalence of undernourishment in the region decreased from 23.7 percent to 13.9 percent. Latin America and the Caribbean also made progress, falling from 65 million hungry in 1990-1992 to 49 million in 2010-2012, while the prevalence of undernourishment dipped from 14.6 percent to 8.3 percent. But the rate of progress has slowed recently. The number of hungry grew in Africa over the period, from 175 million to 239 million, with nearly 20 million added in the last few years. Nearly one in four are hungry. And in sub-Saharan Africa, the modest progress achieved in recent years up to 2007 was reversed, with hunger rising 2 percent per year since then.
Toggle Commented Apr 10, 2014 on PIOMAS April 2014 at Arctic Sea Ice
Thank you for sharing Jim, and I agree that this view does seem to be overstating the MYI, while being in better agreement with HYCOM on structure.
Toggle Commented Apr 9, 2014 on PIOMAS April 2014 at Arctic Sea Ice
Thanks to Chris for a great regional PIOMAS update! One item I noticed in particular is the considerable difference between your gridded view of ice thickness compared to HYCOM: 'Your' view has a lot more ice in the Central AO, while HYCOM is showing a significant branch of thicker ice in the Beaufort and Chuckchi Seas. I hope you have it more accurately placed than HYCOM, as the lower latitudes showing on HYCOM does not bode well for summer melting rates (depending on your view point). And your statement: "I don't expect 2014 to beat 2012, but I do expect a more exciting year than 2013". What is this? ;-) I found 2013 extremely exciting like the thriller where the hero is up against impossible odds, but starts out amazingly well, then almost succombs, and finally makes it through with few casualties. I always favored the underdog..
Toggle Commented Apr 9, 2014 on PIOMAS April 2014 at Arctic Sea Ice
I am refering to this excellent blog entry by Neven last year: And a key abstract from that entry: The Summer Cyclone Maximum over the Central Arctic Ocean Mark C. Serreze and Andrew P. Barrett, 2008, Journal of Climate From the abstract: A fascinating feature of the northern high-latitude circulation is a prominent summer maximum in cyclone activity over the Arctic Ocean, centered near the North Pole in the long-term mean. This pattern is associated with the influx of lows generated over the Eurasian continent and cyclogenesis over the Arctic Ocean itself. Its seasonal onset is linked to the following: an eastward shift in the Urals trough, migration of the 500-hPa vortex core to near the pole, and development of a separate region of high-latitude baroclinicity. The latter two features are consistent with differential atmospheric heating between the Arctic Ocean and snow-free land.
Toggle Commented Apr 8, 2014 on PIOMAS April 2014 at Arctic Sea Ice