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
Neven, In agreement with the many comments above: Thank you very much for having managed this great blog with an even-keeled approach to understanding and communicating changes for the Arctic sea ice. Wishing you well and good luck with the continued house project! Kind regards, John
Toggle Commented 2 days ago on Sabbatical (I hope) at Arctic Sea Ice
OK viddaloo, so then you also agree that for the majority of the time since the Sept minimum and currently, we have slightly more sea ice volume than in 2012?
Toggle Commented Nov 16, 2016 on PIOMAS November 2016 at Arctic Sea Ice
"Yes, I remember! And I'm very happy they went through the trouble of improving their model so that it would become more reliable. If only PIOMAS would do the same, and listen to well–founded criticism!" That is just great, viddaloo, and then since DMI apparently listened to well-founded criticism (Did they?) do we now agree that 2016 has had more sea ice than 2012 for the vast majority of the time since minimum in September? - because we now like the DMI volume model more than the PIOMAS volume model..
Toggle Commented Nov 16, 2016 on PIOMAS November 2016 at Arctic Sea Ice
"2016 minimum Arctic sea ice volume was lowest ever according to DMI" viddaloo, Remember that we were in agreement earlier that the DMI volume model is not reliable, so would it make a difference if it is lower or higher than 2012?
Toggle Commented Nov 15, 2016 on PIOMAS November 2016 at Arctic Sea Ice
Politics is becoming more polarized with both sides screaming at each other - until one or both sides take up more tangible means to defeat the other. This is the scary part.
Toggle Commented Nov 10, 2016 on PIOMAS November 2016 at Arctic Sea Ice
Couldn't agree with you more NeilT - except that Trump should be successful in just ignoring climate change on his watch as he is supported by the type of voters, who wants cheap and plenty gas at any cost. These guys removed the Indians and the buffalo, so no reason why they would feel any different about ice bears or flooding of coastal areas.
Toggle Commented Nov 10, 2016 on PIOMAS November 2016 at Arctic Sea Ice
Thank you for another great update Neven - and best wishes for your other endeavors! Otherwise, what a sad day for moderates: What happened in the US last night is just a continuation of what we have seen in Europe, Turkey, the Middle East and the Philippines over the past few years. The consequences will not be positive for the climate/energy problems or for humans.
Toggle Commented Nov 9, 2016 on PIOMAS November 2016 at Arctic Sea Ice
But yes; most of North America and the central Arctic very warm indeed:
The 'Siberian' cold actually stretches from Morocco to the West Siberian Plain and then again across much of eastern Siberia to Kamchatka. And now the sea ice is causing this weather, not the AO. Great!
wayne, you think PIOMAS is for the uncritical fixated minds, while the erratic noise of Jaxa volume is for the insightful? May peace reach your mind.
Jaxa 2014 volume increased from about 4.000km3 to 11.000km3 during the month of August. With such erratic movement, it is not useful for metrics.
Hi viddaloo, Jaxa does not produce reliable volume numbers, as you can see from the very high up and down ticks. PIOMAS is normally recognized as the most reliable option, so you should use that volume.
viddaloo and D, Sea ice thickness can be calculated in different ways, such as: 1. PIJAMAS (Neven's invention I believe): PIOMAS volume divided by Jaxa extent. (See the monthly PIOMAS updates on this blog). This metric should provide a low average thickness, as it divides by extent, which means some of the ice cover is non-existing, and therefore the actual average thickness should be higher. 2. PIOMAS thickness ( ): PIOMAS divide the volume by the domain, where the sea ice is at least 15 cm thick, but I have not verified if this is area or extent. Due to the minimum thickness required, the PIOMAS average thickness should be a bit higher than PIJAMAS. Both metrics have in common that they reach minimum average thickness by end of October. I cannot find definitions on Wipneus' thickness metric for comparison.
I see where you are coming from viddaloo, when you are looking at these average thickness numbers. However, you need to step back and test against the natural/physical boundaries. Minimum average thickness is typically reached during the last week of October, ie. with current conditions. 0.5 meters average thickness with about 6.000km3 ice volume requires an extent of about 12M km2, but in fact the extent is below 7M km2. 1980s average extent (JAXA) for this day is 9.6M km2.. Therefore, since we have record low extent it is physically impossible also to have a very low average thickness, as it is the growth of new sea ice that causes the low thickness number during the fall season. In fact with warming Arctic waters we should expect the average thickness to drop less in the fall season, simply because ice extent will increase at a slower pace in the warmer waters - as we are currently observing. Neven's PIJAMAS graph shows how 2007 and 2008 saw much larger drops in avg. thickness than in recent years for this reason.
Reaching an average ice thickness of a ½ meter (or less) this year would require a simultaneous volume low record combined with a sea ice extent higher than the average extent of the 1980s, so we probably need to wait a few years for that to happen.
Yes, as pointed out by Sarat also viddaloo, you cannot speak of "loss of thickness" during the freeze period, where ice thickness is increasing. It's just the average thickness metric going down, which necessarily happens every single year - because a lot of thin new ice is created at the boundary of the pack.
"would take us all the way down to less than half a meter in 2016".. Yes, clearly - and imagine what wind would do with all of that ice being less than half a meter thick ;-)
"the loss of thickness over the following month was 30.5 cm".. brilliant idea!
Hi Robert, DMI has about -10C at the Pole - where do you see -2C? -10C still being quite warm compared to surrounding continents, a very interesting setup!
Another comment on current NH temps ( ): I do not recall having seen a situation quite as extreme as this year with very warm Arctic waters and cold surrounding continents, especially on the Eurasian side, where it is quite cold. It will be very interesting to see, how this could impact the CAB and other central seas: Continued cyclonic pattern due to high temporal difference, keeping the water relatively warm, or sudden quick freeze up, as we to some degree has seen in Laptev?
Toggle Commented Oct 26, 2016 on The 2016 melting season in images at Arctic Sea Ice
wayne said: "It is better to analyze with the comprehensive holistic overview, than being bland and generalize meaningless platitudes meant to confuse rather than explain reality." Yes, indeed, which is why the AO should be part of your comprehensive holistic overview. Based on the elements included in your analysis, you expected back in June that a high would develop and move near the Pole. But the high did not develop and the cyclones churned above the sea ice, not the open water. Including the AO in your analysis of the summer-time sea ice development, would appear to have improved your holistic analysis. The AO is one factor among many; timing and distribution of snow cover, movement of highs and lows, changes in current, etc. all play their part, which is why no-one is able to predict weather or sea ice conditions much beyond the next few weeks, and with the current temperature, extent, concentration, volume stats providing the best basis for predicting what the situation will be like a couple of months from now. Currently, the AO- with increased dominance of clear skies, appear to have caused much of the land areas north of the jet stream to have surface temperatures below normal: Whether these below normal temperatures will translate into increased sea ice development will depend on more local weather conditions, but the probability should have increased - although it also seems that under very negative AO, the Arctic temperatures and sea ice development becomes more volatile, probably as a consequence of the more wobbly jet stream associated with blocking highs, which will cause any local weather condition to have a more extreme impact. Looking at past seasons seem to indicated such an increased probability, but evidently many more factors need to be involved to fully explain the sea ice development of each season.
Toggle Commented Oct 26, 2016 on The 2016 melting season in images at Arctic Sea Ice
Hi viddaloo, On the current plunge you said: "Not so much. If you look closer at the data, 2007 & 2012 AAE plunges are all you can compare this amazing October Plunge to." My point is that a 'summer-time plunge' does not compare to a 'fall-plunge': The extent of the Arctic sea ice is much more volatile in summer months, and you therefore see much larger anomalies in summer compared to an average year extent, which is exactly what caused the plunges in 2007 and 2012. The 2012 summer SIE negative anomaly was more than 2M km2 for a period (JAXA, compared to 2000's average), while the current 2016 SIE has a 1.8M km2 negative anomaly. I am not trying to diminish the assessment of the current state though, which is very bad, as the 2016 SIE again is charting into new lows not seen before together with the SIA numbers. Especially the heat in Kara and Chuckchi makes further ice advancement and volume growth very slow, and I expect the next PIOMAS update to confirm the slow growth, with 2016 volume getting near or at record low volume.
Toggle Commented Oct 26, 2016 on The 2016 melting season in images at Arctic Sea Ice
AnotherJourney, Your comments are quite interesting, but this blog is on Arctic sea ice and we aim to stay on topic, so that the blog stays relevant to readers of Arctic sea ice.
viddaloo, I think Jeff is merely pointing out that your plunge only is partly caused by freeze of these next few weeks. Since the refreeze in 2015 was relatively strong for this period, then the plunge for the annual average would deepen further if 2016 freeze would be at the average level. For the same reason we can also assume that the annual average extent will stop dropping or have very limited decrease from around Nov. 15, where the 2015 SIE increase went into a slow increase period.