May is the month when melt ponds first start to form on the floes of the Arctic sea ice pack. Melt ponds are important because they soak up more sunlight than the ice would, speeding up the melting process and thus preconditioning the sea ice. When there is lots of melt ponding, something I call melting momentum is built up, sustaining a stable melting rate throughout the rest of the melting season, as we saw in 2011 and 2012. Of course, the reverse is also true, as we saw in rebound years 2013 and 2014.
Because this preconditioning through melt ponds seems to be correlated to the September minimum, scientists are trying to determine the so-called melt pond cover fraction (the percentage of total ice pack area covered by melt ponds) in different ways. Some look at satellite observations, like Anja Rösel from the University of Hamburg did back in 2011, using MODIS satellite data (see here). Others use models, like David Schröder from the University of Reading (see here, and more on that below). Yet others, like Christopher Cox from CIRES, look at radiation data around the Arctic to estimate how much sunlight is reaching the ice pack (I attended Dr. Cox' presentation on this subject at the EGU general assembly this year).
Even though it's very difficult to determine the exact amount and distribution of melt ponds, we can at least compare weather conditions from year to year, as melt ponds come into being due to above freezing temperatures and solar radiation (ie open skies due to high pressure), or a combination of the two. Chris Reynolds has a detailed blog post on atmospheric conditions during all of May on his Dosbat blog, but below I'll be looking at those conditions compared to those of other years during May.
I've divided May up into two halves, and here's the first map showing average temperature anomaly and sea level pressure from May 1st to 15th:
As can be seen, May started out extremely cold in the Central Arctic Basin, with anomalously warm temps along the coasts of the Beaufort and Kara Seas. Except for 2011, no other year in this comparison was as cold in the heart of the ice pack. In that sense 2015 started out even worse (for melting) than the two rebound years 2013 and 2014, where a very low melt pond fraction cover during May (and June) made it virtually impossible for those melting seasons to reach the top 5 lowest September minimums.
These extremely low temperatures are also reflected on the DMI graph that shows (modelled) temperatures above 80° latitude:
The graph also shows that the extreme dip was followed by a steep climb, even traversing the green average temperature trend line. This suggests weather conditions flipped during the second half of May, so here's the comparison map for May 16th-31st:
The cold has disappeared from the Central Arctic, with the heat expanding in the Beaufort and Kara Seas, the effects of which were discussed in ASI 2015 update 2. Only 2011 seems to have been warmer, with 2010 and 2012 showing anomalously high temperatures spread all over the Arctic. If you didn't notice, go back and check how 2010 looked on the first map an second map as well: extremely warm (relatively speaking) and extremely high sea level pressure, meaning clear skies. It's no wonder PIOMAS shows a huge volume drop in this period in 2010. I guess it's the perfect preconditioning for a high melt year.
So, with 2015 starting out extremely cold during the first half of May, and then almost the reverse in the second half of May, what can be said about the melt pond cover fraction? Luckily I received some info on that from Dr. David Schröder, who I've met at the EGU General Assembly two months ago. In an e-mail he sent me three distribution maps, produced by his melt pond model, showing melt pond anomalies for the years 2012, 2014 and 2015 compared to the average for the last 10 years (click for a larger version):
Dr. Schröder added this caveat: "Be aware that we do not know how accurate the locations of our pond maps are and that the relative and absolute numbers for May pond fraction are very small."
2015 can't compare to 2012 really, but it does show a slightly less negative melt pond anomaly than 2014. Just like last year Dr. Schröder and his team use this result as a prediction for the SIPN 2015 Sea Ice Outlook (the first summary of which will be released soon), and Dr. Schröder has given me permission to reproduce the text accompanying the three maps above:
Based on our simulated May melt pond fraction we predict a September 2015 mean ice extent for the Arctic of 5.1 +/- 0.5 Mill. km2. Our value is slightly lower than in 2013 (5.4 Mill. km2) and 2014 (5.3 Mill. km2), but considerably larger than in 2012 (3.6 Mill. km2). The attached 3 figures show the anomaly of May melt pond fraction in May 2015, May 2014 and May 2012 with respect to the mean over the period May 2006 to May 2015. Locations which show no correlation with the September ice extent are masked.
In May 2012 there are positive anomalies of pond fraction with values between 0.5 and 2% above the last 10-year average, whereas in May 2014 negative anomalies between -0.2 and -1% occurred. In May 2015, the anomalies are mainly negative, but weaker than in 2014. The pond fraction does mainly depend on the atmospheric conditions in May and the pre-conditioning of sea ice (sea ice thickness, area fraction of thin ice).
While the atmospheric conditions were quite "normal" in May in average, the ice is thicker in April 2015 in our model simulation compared to previous years. The increase in ice thickness and volume is also confirmed by the PIOMAS simulation: maximum ice volume in 2015: 24388 km3, in 2014: 23104 km3 and in 2011: 22677 km3. The given uncertainty of our prediction of 0.5 Mill. km2 is mainly caused by ice drift during summer and the atmospheric conditions during June. Given the current situation we do not expect a new record minimum for Arctic summer sea ice in 2015.
That certainly makes sense, because our last indicator of melt pond cover fraction shows that very few melt ponds have formed since the start of the melting season:
CAPIE, or compactness, is calculated by dividing Cryosphere Today sea ice area data with IJIS sea ice extent data, which gives us a percentage. Short explanation: the Arctic is divided into grid cells. When 15% or more of a grid cell is covered with sea ice it will be counted as 100% covered with ice for extent (meaning the total km2 of the grid cell will be counted for total sea ice extent), whereas the exact amount of km2 that is covered with sea ice will be counted for area. This means that area will always be lower than extent, because of leads or open water within the grid cell.
Here's the thing: melt ponds fool the satellite sensors into thinking that there is open water where there is none. This will get counted for area, but not for extent (unless a melt pond is so big that the 15% threshold is passed). So, if there are a lot of melt ponds, area will go down faster than extent, and the percentage will drop.
In this case the reverse is true: extent has been very low for weeks now, but area remains average, and so the percentage is high. Because CT SIA and IJIS SIE numbers aren't perfectly compatible (grid cells for CT SIA are much bigger, for instance), I also show this compactness graph, made and updated by commenter Wipneus, that uses SIE and SIA data with higher resolution (smaller grid cells) from the same data providers, which basically shows the same:
There aren't many melt ponds right now, relatively speaking, just like in 2013 and 2014, which means that not much melting momentum is being built up, which means that sea ice decline will slow down as soon as the Arctic is cloudy, which means that chances that 2015 will make the top 3, let alone get close to record territory, look rather slim right now. Which is good for the sea ice and the Arctic in general, of course.
At the same time nothing is certain as of yet, as there are still two weeks left in June for melting momentum to be built up, and going by this thickness map based on SMOS data for February and March - that I found in this presentation - there is a lot of relatively thin ice around the Arctic, similar to 2012:
Warm and sunny weather can still do a lot of damage, especially in the Beaufort and Chukchi Seas where a lot of multi-year ice has been transported to over winter. I'll report on current conditions in the ASI updates (next one coming out at the end of this week) and cover the melt pond situation during June next month.
Those maps are difficult to understand. Melt pond fraction is reported only for very specific locations, including a strange place in the middle of the Atlantic
Posted by: navegante | June 15, 2015 at 01:18
Thank you Neven, for a well thought out, balanced overview of the situation in the Arctic at this point.
I appreciate David Schröder's team melting pond assessment this year
http://neven1.typepad.com/.a/6a0133f03a1e37970b01bb08427a8c970d-pi
There is no doubt that melting ponds greatly affect the melting season locally, and thus his data is important and very well appreciated.
Did you obtain any information on how David Schröder's team determines this info ?
Posted by: Rob Dekker | June 15, 2015 at 10:22
NSIDC sea ice concentration has dropped substantially today. That will not be reflected in Cryosphere Today Area numbers until Wednesday when it will drop by a massive 340k.
The first sign of this was an explosion of melt area in today's ADS-NIPR Jaxa thickness/melting maps (https://ads.nipr.ac.jp/vishop/vishop-monitor.html). A sequence was posted at the forum (http://forum.arctic-sea-ice.net/index.php/topic,1112.msg54089.html#msg54089). This is also the place to look at tomorrows and the day after tomorrows CT numbers.
Since extent did "only" drop by about 75k, the compactness calculated from NSIDC concentration has taken a plunge as well and is now at similar levels as 2013 and 2014.
To stay there (at 2103/14 levels), let alone get into record territory area will have to keep falling in the next few days. Today has shown it is possible.
Posted by: Wipneus | June 15, 2015 at 17:07
340K? Wow, that's massive. A quick look at my CT SIA spreadsheet shows a drop that big hasn't happened since 2008.
Posted by: Neven | June 15, 2015 at 17:43
Thanks again for a nice summary, Neven.
Another 'interesting' moment, I'd say--hard to predict what turn will happen next, especially with that prospective 340k Wipneus is talking about.
Posted by: Kevin McKinney | June 15, 2015 at 18:45
Dumb question time for me. I had noticed that the spectacular early start for extent and area was returning to earlier (still lower) norms, so how does the above-mentioned concentration figure into that (not too technical, please, if possible).
Meanwhile, Wipneus's earlier link needs to be edited to remove ")." or use this, stolen/done:
https://ads.nipr.ac.jp/vishop/vishop-monitor.html
Posted by: Susan Anderson | June 15, 2015 at 19:22
Rob,
It's a melt pond model augmentation to CICE which is driven by NCEP/NCAR atmospheric forcing.
Navegante,
Those are anomaly plots, or difference from the long term mean. Where they are white the difference from the long term mean is too small to display.
Posted by: Chris Reynolds | June 15, 2015 at 20:45
Thanks, Susan. Links fixed.
Are you referring to the low (and early) maximums? Compactness is usually high for most of the year, around 95%. It doesn't tell us much then. It's when the melting season gets going, and melt ponds start to form and/or the ice pack gets dispersed (open water between floes), that area will go down faster than extent, and the compactness percentage follows (see explanation in the post).
Is that what you mean?
Posted by: Neven | June 15, 2015 at 21:20
Susan,
The arctic region is covered by a grid, you can see the NSIDC 25km grid by going to cryosphere today, the regions map there is a grid, each pixcel represents one grid box.
Satellite microwave brightness is used to work out the concentration of ice in each grid box. And concentration is given in a table of numbers, one for each box.
Wipneus uses this gridded data to work out area and extent. You know what they are I presume?
Basically, if concentration drops away from the ice edge within the pack area will drop. But unless concentration goes below 15% extent won't drop. In that case Neven's CAPIE index will fall, and we'd say that the pack becomes more dispersed. Where most of the loss of concentration is from the region around the ice edge both area and extent fall at the same rate. In such a situation Neven' CAPIE index would remain roughly level.
I use compactness, area divided by extent, that has been fairly average all June so far. this suggests that through June so far the loss of ice concentration within the pack has bee normal.
In years like 2007 & 2012, there was a lot of loss of concentration from within the pack, so by this time in June CAPIE (and compactness) were falling faster than normal.
Hope this helps, if not just ask.
Posted by: Chris Reynolds | June 15, 2015 at 21:31
I think as Wipneus' post indicates - a triple century on Wednesday - we do not possess information about all of the forces currently at work.
We are dealing with a moving target, and I'm not sure that assumptions based on a previous years events will translate accurately into what will transpire in 2015.
I suspect that Dr. Schröder's estimate is far, far to conservative. Based on the 2015 Maxima, it would require that the net melt would be less by nearly 1 million KM2 than has happened in the last 5 years.
Since 2007 every year has had more than 10 Million KM2 of melt; considering 2015's maximum was slightly over 14 million KM2, a 5 Million KM2 minimum demands less melt than has happened since 2006.
IF current weather conditions were on a par with 2013, I *might* think that possible; however, in the face of conditions which are highly unfavorable for retention of ice, I find that highly unlikely.
I'm not yet certain that we will reach a new minimum, but I am confident in spite of good Dr. Schröder's prediction, that we will pass 5 Million KM2 by a wide margin.
Posted by: jdallen_wa | June 16, 2015 at 07:47
Modest re-statement;
SIA losses have been consistently 10M KM2 since 2006.
Looking at IJIS data, there have been sub 10M KM2 years, but none less than 9.5 M KM2 (2014); the average annual extent loss from 2007 forward is approximately 10M KM2.
Even considering this oversight on my part, the upshot of this is, Dr. Schröder is low by at least 500K KM2; and that is only if the melt season is on a par with 2014. So far, it shows no sign of cooperating with our desire to preserve the ice.
Posted by: jdallen_wa | June 16, 2015 at 08:01
According to Wipneus' concentration maps :
https://sites.google.com/site/arctischepinguin/home/amsr2/grf/amsr2-compact-compare.png
the 'course' (25 km^2) NSIDC concentration dropped very quickly to normal levels, but the high resolution (3.125 km^2) concentration is still anomalously high.
What I make of that (Wipneus please correct me if I'm wrong) is that there is a lot of thin ice at the edges turning to slush rather quickly, but the interior of the pack is still quite "white" and resilient.
I think the jury is still out there on where 2015's minimum will end up.
Posted by: Rob Dekker | June 16, 2015 at 11:52
Andrew Slater projection have just collapsed in the last few days.
http://cires1.colorado.edu/~aslater/SEAICE/
Posted by: Yvan Dutil | June 16, 2015 at 13:49
Thanks Neven and Chris Reynolds, that is kind and helpful as well. (Yes, I meant the very early maximums and subsequent deviation from previous years.) There are so many different weird things going on everywhere, it's hard to tolerate the general embrace of blindness, but getting ahead of ourselves doesn't help either.
And since I'm always boring on about these, here's a better link for the polar view of the water vapor animation (because you can slow it down):
http://mp1.met.psu.edu/~fxg1/SAT_NHEM/animwjap.html
I continue to be fascinated by earth's venting systems, in particular the way all that cyclonic activity in the Pacific is sending heat north, while at least some of Alaska continues ridiculously hot.
Posted by: Susan Anderson | June 16, 2015 at 14:13
Yes and it is a bit of a puzzle. Compactness is depending on resolution, but melt ponds are small (I think) compared even with the 3km resolution. So in this case resolution should not matter. At the very least some response should be seen.
The SIC product differ in more aspects than resolution, the microwave bands and calculations (known as "algorithms") are all different. The NSIDC uses the NT (NASA Team) algorithm, that is known to underestimate concentration especially during melting conditions. More than other algorithms.
Melt ponds that deserve the name "pond" should affect all algorithms equally, the microwave bands used cannot distinguish ponds from open water.
Therefore I think that the melt effect we are seeing is not melt ponding yet but rather the change from dry ice to wet ice, dry snow to wet snow, ice covered with snow to bare ice.
So will this melting effect continue? Will ponds form and affect the other ice algorithm as well?
FYI, I posted this on the forum today:
Posted by: Wipneus | June 16, 2015 at 19:20
Acidification takes toll on Beaufort Sea; threats loom in Chukchi and Bering
With their low temperatures that hold onto the carbon dioxide absorbed from the atmosphere, their shallow depths, their rich supply of marine life and carbon dioxide carried in by currents from elsewhere in the world, and their increasing supply of runoff from melting glaciers and glacier-fed rivers, Alaska’s ocean waters are known to be highly vulnerable to acidification.
Now comes a finding that the Beaufort Sea has already crossed an ominous ocean acidification threshold, and the Chukchi Sea and Bering Sea will follow in the foreseeable future, with water conditions that would be corrosive enough to cause many marine species to struggle. ..................................
The Beaufort Sea has already reached a state where its surface waters, on average throughout the year, hold too little calcium to fully support shell-building organisms, according to the new findings.
Based on measurements made during research cruises in 2011 and 2012 aboard the U.S. Coast Guard icebreaker Healy, that threshold was crossed in 2001, the scientists found.
Alaska Dispatch News
Posted by: Colorado Bob | June 17, 2015 at 00:03
Lots of new melt ponds over the last few days
Esp for buoys 10,11 and 12
http://obuoy.datatransport.org/monitor#buoy12/camera
And like Susan I've been watching the huge swirls in the Pacific sending warm air north and cold air out seemingly pushed out the other side ( so to speak :)
I think melting will be pretty significant this year, maybe not a record but worryingly close.
Posted by: Kate | June 17, 2015 at 11:08
Kate wrote:
Me thinks it could be handy to have them all into one and the same page. Feel free to download the file by right clicking onto the bold ecc... ecc...
- Obuoys 3 and 13 are still “grounded”, but still, its good to have them pronti.
- As a bonus both the cams 1 & 2 from Washington.edu
Posted by: Kris | June 18, 2015 at 03:15
Question -- sanity check on this?
https://robertscribbler.wordpress.com/2015/06/18/arctic-sea-ice-area-drops-320000-square-kilometers-in-just-one-day/
The story is, vaguely, attributed to Neven's Sea Ice site, but I haven't found the source here yet.
Posted by: Hank Roberts | June 19, 2015 at 19:41
See comment on this same post,(Wipneus)
http://neven1.typepad.com/blog/2015/06/melt-pond-may-2015.html?cid=6a0133f03a1e37970b01b8d12831d9970c#comment-6a0133f03a1e37970b01b8d12831d9970c
Sources are there.
However the story is written in a pretty sensationalist way. He forgets to mention that such drop is not only ice gone but also ponds fooling the satellite sensor and making believe it is open water and ice is gone.
No, a piece of ice cap of the size of New Mexico did not disappear overnight.
Plus, there have been a few days of slow area decline as well, before and after that monster drop
Posted by: navegante | June 19, 2015 at 19:58
I was talking about Robert Scribbler's story, not Wipneus' :)
Posted by: navegante | June 19, 2015 at 20:06
Navigante wrote:
To put it mildly. I rather would say it's misleading as the published Cryosphere (not Cyrosphere!) chart shows SIE, not Sea Ice Concentration what the 340.000 Square kilometer are about - so it has nothing to do with Neven's ''centuries''.
And that it solely is about concentration can easely be monitered at the UNI-Bremen maps
from yesterday and the days before.
Bottom line, we can miss that kind of input as much as Cincinattus' contributions.
Incidentally, yesterday ADS-NIPR showed a drop of only 20 square km in extent.
Posted by: Kris | June 20, 2015 at 03:42
Confirmation,today, for the 19th of Juin ADS-NIPR states only a minus of 14 square km in extent, in respect to the 18th.
Whereas UNI-Bremen shows a massive drop in concentration.
Me thinks it's a phenomena we haven't seen hitherto ...
Posted by: Kris | June 20, 2015 at 09:12
Right now there is massive melt ponding and significant open water over quite an area. Checking the Barrow website shows temperatures at 10C and checking the landfast monitoring station
http://amaru.gina.alaska.edu/data/graph/mbs_barrow/BRW_MBS.jpg?graph=ProfileGraph
shows the same plus the fact that the shallow land fast water is now at around 0C.
So it's not going to be long as ice.
As ever, it will depend on the weather and the insolation it provides....
That; is yet to be seen.
Posted by: NeilT | June 20, 2015 at 18:36