The 2015 melting season

[viddaloo]

Icelook mar30: Average extent 6^th lowest in 32 days, average volume will be 6^th in 5 days, and p1k (Piomas minus 1000) will be 5^th in 41 days. I promised last week that we'd cross the 10.28 million km² line for annual average extent by Mar 30, however it now looks like the slowdown of the past week or so means it will take about another week. Current weekly delta at 3802 km²/week would enable us to slip below 10.28 by Easter Monday, or Apr 6. The graph doesn't go below 10.28 at all, and points at May 1st for going as high as 2014 average extent. However, the background figures suggest this forecast is about to change quite dramatically, but as always with the Arctic: Only time will tell.


[chart faq]

PS: DavidR's 'plateau' of flat–ish extent within 200 k km² below max for 5–day averages is coming to an end really soon. The plateau for daily extent was left yesterday (meaning we're below 13.94 minus 0.2 = 13.74 million km²), and the 5–day averages are expected to fall. If statistics is anything to go by, and if the record–low and record–long plateau of 2015 is caused by increased ocean heat content, 2015 may well be the year that returns Arctic sea ice to the rapid downward trend of 2010–2011–2012, after some years of 'reaction' to shock (or what do I know). Will the new minimum come in 2015, or will we only prepare the ground for a truly shocking (though somewhat expected) new minimum in 2016?

[jdallen]

The models just lay the smack-down on the Western 1/2 of Eurasia the next two weeks

...

There is already a very very large region over the Western side of Eurasia that is about to  vanish off the Rutgers/nic maps where it's barely 50%.

I believe it is the same region with unusually low snow cover for the season as well.  Time to check the coverage maps...

[icefest]

I wish he/she would do the same through the winter.

Or even in the El Nino thread!,
Good to see you back friv!

[Neven]

Friv is back. The melting season has started. 

Speaking of forecasts: I'm replacing the SLP Patterns page on the ASIG (too much work, not enough interest) with this Forecasts page. It's not live yet, but it will be next week or so.

But I need your thoughts on something. I've got SLP, Surface wind speed and Temperature anomaly there. But I'm doubting whether I should replace Temp anom with just Temp. I like temp anom, because it shows where the anomalous stuff is taking place, and I always like to compare to previous years or averages. But it's also good to know whether them temp is still freezing or not.

I guess this is an eternal dilemma. A solution might be to do 4 columns instead of 3, but I prefer 3, because otherwise the images become too small IMO.

So, what do you think/prefer?

[crandles]

Could it work with 4 sections vertically?

i.e. 2 rows for 6 days of SLP
2 rows for 6 days wind speed
2 rows for 6 days temp anomaly
2 rows for 6 days temp

or do you need slp and wind speed next to next?

.

It might be a case of people being used to what they use. I tend to look at these

from http://www.wetterzentrale.de/topkarten/fsecmeur.html

[cesium62]

Showing forecasts of what is happening at 500hPa or 800hPa shows little of what is happening at ice level.

Ima newb: Where is 500hPa and 800hPa with respect to ice level?
thanks.

[cesium62]

Friv is back. The melting season has started. 

I'm holding out 'til 15 April.  I think we might get a tax refund this year.

[seaicesailor]

Friv is back. The melting season has started. 

Speaking of forecasts: I'm replacing the SLP Patterns page on the ASIG (too much work, not enough interest) with this Forecasts page. It's not live yet, but it will be next week or so.

But I need your thoughts on something. I've got SLP, Surface wind speed and Temperature anomaly there. But I'm doubting whether I should replace Temp anom with just Temp. I like temp anom, because it shows where the anomalous stuff is taking place, and I always like to compare to previous years or averages. But it's also good to know whether them temp is still freezing or not.

I guess this is an eternal dilemma. A solution might be to do 4 columns instead of 3, but I prefer 3, because otherwise the images become too small IMO.

So, what do you think/prefer?

...

It might be a case of people being used to what they use. I tend to look at these

from http://www.wetterzentrale.de/topkarten/fsecmeur.html

+1
IMHO the wetterzentrale pressure plot would give you the space you need. It gives info of SLP, 500 mb (which does have a lot of importance), and winds indirectly, by observing  the distance between isobars 
Then you have space for both anom and actual temps, three columns total

BTW for some reason I can only reach the third column half way. Thanks for considering these inputs

[viddaloo]

IJIS:

13,695,140 km²（March 30, 2015）down 29,112 km² from previous.

[Michael Hauber]

Showing forecasts of what is happening at 500hPa or 800hPa shows little of what is happening at ice level.

Ima newb: Where is 500hPa and 800hPa with respect to ice level?
thanks.

Full atmospheric pressure is roughly 1013 hPA.  So 500 and 800 are about 50% and 20% of the atmosphere above the ice level surface, or maybe very roughly 2km and 5km.

Temperature at ice level cannot rise above the melting point of the ice (0 for fresh water multi year ice, about -2 for salty first year ice) until the ice is melted, and 850hp is a reasonable representation of how much heat is available in the atmosphere above the ice to melt ice.

[anthropocene]

Showing forecasts of what is happening at 500hPa or 800hPa shows little of what is happening at ice level.

Ima newb: Where is 500hPa and 800hPa with respect to ice level?
thanks.

Full atmospheric pressure is roughly 1013 hPA.  So 500 and 800 are about 50% and 20% of the atmosphere above the ice level surface, or maybe very roughly 2km and 5km.

Temperature at ice level cannot rise above the melting point of the ice (0 for fresh water multi year ice, about -2 for salty first year ice) until the ice is melted,

If somebody comes on here with knowledge or data that shows otherwise I will be happy to be proved wrong -  but I don't think this is true. If the argument is that the heat energy must melt the ice before the temp. can go above the melting point then the same argument would apply to snow fields. There are many examples of temps well above zero but lying snow still being present ( the snow (slowly) melting admittedly). 

and 850hp is a reasonable representation of how much heat is available in the atmosphere above the ice to melt ice.

True - if the normal atmospheric conditions apply and the temp. gets less with altitude so the measured temp. is less than that closer to ground level. But what about the case of a temperature inversion?  Again I would appreciate it if somebody with more experience would provide their input - but due to its cold temperature, latent heat content and high albedo, a temperature inversion is something  that I would expect to be quite common above the sea-ice pack. Additionally, it is my proposal that if you have a temp. inversion, any warmer invading air will ride up above the denser colder air sitting on top of the ice.

[viddaloo]

Ahem, we have now definitely left the Plateau and are rushing down towards a very likely new minimum record, having A) the lowest extent of the 5 top low years in the Plateau plot, B) the lowest AND longest plateau, and C) the first crossing of the 13.7 million km2 line of these 5.

That is very exciting! Some enthusiasm might be in place after a record long and rather boring plateau existence for the last 1.5 months.

[slow wing]

Anthropocene, just wondering if snow fields might be qualitatively different to sea ice because snow is a much better insulator than ice and so a much less effective heat sink at zero degrees?

[LRC1962]

Showing forecasts of what is happening at 500hPa or 800hPa shows little of what is happening at ice level.

Ima newb: Where is 500hPa and 800hPa with respect to ice level?
thanks.

Full atmospheric pressure is roughly 1013 hPA.  So 500 and 800 are about 50% and 20% of the atmosphere above the ice level surface, or maybe very roughly 2km and 5km.

Temperature at ice level cannot rise above the melting point of the ice (0 for fresh water multi year ice, about -2 for salty first year ice) until the ice is melted,

If somebody comes on here with knowledge or data that shows otherwise I will be happy to be proved wrong -  but I don't think this is true. If the argument is that the heat energy must melt the ice before the temp. can go above the melting point then the same argument would apply to snow fields. There are many examples of temps well above zero but lying snow still being present ( the snow (slowly) melting admittedly). 

and 850hp is a reasonable representation of how much heat is available in the atmosphere above the ice to melt ice.

True - if the normal atmospheric conditions apply and the temp. gets less with altitude so the measured temp. is less than that closer to ground level. But what about the case of a temperature inversion?  Again I would appreciate it if somebody with more experience would provide their input - but due to its cold temperature, latent heat content and high albedo, a temperature inversion is something  that I would expect to be quite common above the sea-ice pack. Additionally, it is my proposal that if you have a temp. inversion, any warmer invading air will ride up above the denser colder air sitting on top of the ice.

Maybe the Arctic is different. but I have lived in the part of the world where a lot of snow falls. You can easily get 10C temps with 2m of snow on the ground. Snow does not stay around very long in those conditions although wind does play a major part at that point. Evaporation will keep the temps down from where the temp could have potentially gone to, but just because you have snow and/or ice around does not mean you can not have high temps. That is how you get major flooding events in the spring in snow country.

[Meirion]

The http://cci-reanalyzer.org/Forecasts/ for April 6 almost looks like a dagger of warm air pointing at the Pole. Wonder if we could end up with clear blue water to the Pole this September even without breaking 2012 record. Of course early days and summer weather is what really counts.

[Yuha]

Maybe the Arctic is different. but I have lived in the part of the world where a lot of snow falls. You can easily get 10C temps with 2m of snow on the ground.

On snow covered land there are trees and other objects that can catch the solar energy and warm up the air. On sea ice there is nothing. The surface air can get warm near the coast if the wind is coming from the land. But in the central arctic far away from coasts any warm surface air would have traveled a long distance over the ice and cooled down.

The recipe for melting ice in the central arctic seems to be:

1. Warm air at 850hPa and clouds, creating a lot of downwelling longwave radiation.
This seems to be the ideal weather for melting the snow on top of the ice.

2. Once the snow has melted and melt ponds have formed, remove the clouds and let the sun do its job. If new snow covers the ice, go back to step 1.

Note that my only "expertise" is following this forum and the ASIB for a few years, so please correct me if I'm wrong.

[BornFromTheVoid]

The ability of the ice to hold surface air temps at or around 0C can be clearly seen on the summer segment of the DMIs temperature graphs for north of 80N.

http://ocean.dmi.dk/arctic/meant80n.uk.php

[jbatteen]

Temperature at ice level cannot rise above the melting point of the ice (0 for fresh water multi year ice, about -2 for salty first year ice) until the ice is melted, and 850hp is a reasonable representation of how much heat is available in the atmosphere above the ice to melt ice.

Maybe the Arctic is different. but I have lived in the part of the world where a lot of snow falls. You can easily get 10C temps with 2m of snow on the ground.

On snow covered land there are trees and other objects that can catch the solar energy and warm up the air. On sea ice there is nothing. The surface air can get warm near the coast if the wind is coming from the land. But in the central arctic far away from coasts any warm surface air would have traveled a long distance over the ice and cooled down.

I have to agree with LRC here.  I've lived in Minnesota and South Dakota for all but a couple of years of my life here and there.  It's snowed every month of the year in Minnesota.  In about half of Minnesota and almost the entirety of the other great plains states, there really is nothing to catch or reflect the sun.  Where it's flat and all there is is grass, there's nothing but white as far as the eye can see.  In the spring time, when temperatures vary wildly, I've seen the top few inches of snow melt and turn into a sheet of ice thick and solid enough you can walk on it and not fall through.  In either condition, snow or ice on the surface, temperatures well into the 50s and 60s are possible with warm air advection on strong winds.  Temperatures up to 40 are possible in almost any condition, clouds, sun, calm wind, you name it.

Ice melt and temperature are correlated but it's by no means 1:1.  I've seen 40 degrees and cloudy where essentially zero snow melted for the day due to lack of insolation.  Just last week, we had about 10" of snow on the ground with a solid coating of ice on the surface due to melt and refreeze, and a 60 degree sunshiney 30+mph wind day removed almost the entire snowpack in a day.  With little to block the wind, creeping up on 24 hour sunshine, and where pretty much every source of air for advection is further south where it's warm, I see no reason the Arctic couldn't get above freezing before the ice melts.

[sedziobs]

I think advection of warm air can result in above zero air over smaller ice/snow covered areas.  But, as BFTV points out with 80+ latitude average summer temps, the entire Arctic acting as a heat sink is too much for the advecting heat to overcome.  It's a problem of scale.

[seaicesailor]

Just a small comment, in *completely* calm air with *only* snow or ice many miles around, temperature cannot go higher than 32F (a bit lower for sea ice), since air in contact with snow/ice acquires its melting temperature (thermodynamic principle)
If snow free urban or vegetation elements, or warm winds, temperatures will rise, but there will always be a small, even milimetric, layer of air right on top of snow/ice surface, at 32F, thermodynamic principle.

[Peter Ellis]

[...]I see no reason the Arctic couldn't get above freezing before the ice melts.

It depends at what height you're talking about.  If you put your thermometer at head height, knee height, ankle height or 1mm above the snow surface, you will get different answers.

Fundamentally, the surface itself will be forced to equal melting temperature (0 to -2 degrees depending on salinity), and if the overlying air is warmer, there will be a localised inversion.  It cannot physically be otherwise: the important factor is the length scale over which that inversion occurs.  On a windy day, the air above the surface will be well-mixed, and the inversion confined to the immediate boundary layer.  On a still day, the inversion may be deeper.

The effect of these effects in various models (and the much sparser experimental data) will vary depending on how many atmospheric layers the model uses, and what temperature it's reporting - e.g. the surface temperature or the temperature at 2m above the ground.

[seaicesailor]

That's beautifully explained. Talking about inversion, last year it was very foggy. What will happen this year?

[seaicesailor]

And talking about last year, anybody knows how much snow is out there over the ice compared to last year?

[jbatteen]

[...]I see no reason the Arctic couldn't get above freezing before the ice melts.

It depends at what height you're talking about.  If you put your thermometer at head height, knee height, ankle height or 1mm above the snow surface, you will get different answers.

Fundamentally, the surface itself will be forced to equal melting temperature (0 to -2 degrees depending on salinity), and if the overlying air is warmer, there will be a localised inversion.  It cannot physically be otherwise: the important factor is the length scale over which that inversion occurs.  On a windy day, the air above the surface will be well-mixed, and the inversion confined to the immediate boundary layer.  On a still day, the inversion may be deeper.

The effect of these effects in various models (and the much sparser experimental data) will vary depending on how many atmospheric layers the model uses, and what temperature it's reporting - e.g. the surface temperature or the temperature at 2m above the ground.

Yes that's certainly true.  I guess I got a little carried away in my previous post, my apologies.  The main point I was trying to make was that ice or snow on the surface doesn't 100% guarantee an air temperature at or below freezing, there are nuances.  But overall I think we're mostly on the same page.

[Michael Hauber]

I did mean strictly surface temperature, as in rest a thermometer directly on the ice.  I do realise that temperature can tend to change in the air as you move away from the surface, but was rather surprised that temperatures above 2 meters of snow can be measured at 10C, (presumably at a meter or two above the surface?)

From past observation to get warm air at 850HP in the Arctic you either need a significant southerly wind pulling air in from further south, or a big fat high pressure system.  With a strong southerly there will be significant mixing to the surface due to turbulence, so significant heat reaching the ice.

In the case of a big fat high pressure system there is likely to be an inversion.  However temperatures don't get all that high in such a situation - probably around +4 C is the highest I've seen above sea ice in such a situation, compared to maybe +16 in a strong southerly.  I'm not sure what happens in terms of heat mixing down to the ice in such a situation - the inversion should tend to keep it out, but a strong high should also mean sinking air which could push the heat down?  But one thing I do know in such a situation the sunshine will be relentless and presumably the dominant surface melt factor - at the height of summer significantly stronger than the solar heating at the equator.

[epiphyte]

Not to say that many of the points made in the surface temp discussion aren't valid - but I couldn't resist mentioning that my kids and I took a walk around Lake Harriet in southwest Minneapolis this afternoon... The lake is still frozen (other than for about 10' right at the edges, where it's only a couple of feet deep) - but we were all in shirtsleeves.

Even directly downwind of the ice the air temp was well above 60F. That went all the way down to the ground, too... We actually spent half an hour or so making a sandcastle on the beach!

[Michael Hauber]

Not to say that many of the points made in the surface temp discussion aren't valid - but I couldn't resist mentioning that my kids and I took a walk around Lake Harriet in southwest Minneapolis this afternoon... The lake is still frozen (other than for about 10' right at the edges, where it's only a couple of feet deep) - but we were all in shirtsleeves.

Even directly downwind of the ice the air temp was well above 60F. That went all the way down to the ground, too... We actually spent half an hour or so making a sandcastle on the beach!

That's crazy.  60F is far too cold for short sleeves. 

[LRC1962]

@ MH Sorry about missing the point of surface temps. Would have answered differently. As to shirt sleeves. All depends on what previous temps were. Knew about a guy visiting Toronto from Yukon I believe. Went from -60C to -10C and decided that shorts and t-shirt still were on the warm side. I remember in my teens when temps would fall to -20C and stay there. In the spring when it got to -5C I was in t-shirts.
@BFTV: No question. Unless you have a lot of heat coming into an area (am talking in the area of 10C+) then because of the size of region the microclimate of the area would prevail and contain the temps. On the other hand if there is instability of the region (such as rotten ice, warm waters) then an air system bring in a continuos new supply of heat can make rapid changes to the area.
Poor illustration, but trying a valid thought experiment. If you have 10 litres of ice and room is set at 0C and you added 1 litre of hot water. The hot water would likely freeze. On the other hand if what you added was not 1 litre of hot water, but poured hot water continuously then you could rapidly melt that ice and warm the air. As the examples you pointed to,the supply of heat entering the system was limited and therefore got cooled down but the lack of heat in the local environment.
The big question this year is how much heat will it take to melt what ice there is considering the obvious lack of ice making capacity in the system this winter, and how much heat will be coming into the system. On the Atlantic side you have the cold spot which could make changes to how much heat enters and where it will enter. On the Pacific side there appears to be at least a mild El Nino developing, which will affect the Arctic, but when and how much. questions, questions??

[viddaloo]

IJIS:

13,665,311 km²（March 31, 2015）down 29,829 km² from previous.

2015 with a likely 103% bigger melt this week than 2011:

[anotheramethyst]

slightly off topic (sorry).  im sure im not the only one here who's heard of the pan evaporation rate (a farmer's measure, how fast does a pan of water evaporate).  well recent studies of the pan evaporation rate determine that sunlight is a more powerful driver of evaporation than temperature (and aerosols have contributed to a slower rate of evaporation worldwide).  i mention this because so many people here always talk about how fast the sunlight melts the ice, moreso than higher temperatures.  these studies would support this.  naturally i would think energy inputs would affect both phase changes similarly, but i know the arctic is a very complex place full of intriguing maths that are far beyond me.  also this early in the year, who can say how much sunlight can do?  anyway my point is we can argue about what temperature it is all day long, but without also looking at the other contributing factors, what happens next is anybody's guess.

[LRC1962]

@anotheramethyst: Thank you for mentioning that. I was thinking along those lines as well, but as I am totally ignorant of that topic I held me piece on that idea. Closest I can get to it is this article in relation to land ice sheets . Not sure if that helps or not.

[1rover1]

That is how you get major flooding events in the spring in snow country.
[/quote]

In snowy mountain country it is rain, warm rain on snow and ice in the mountains will flood the valleys below.  I imagine rain on ice will melt it in the arctic as well.  And warm air is one thing, but warm moist air holds a lot more energy and melting power than warm dry air.  Wind will melt the snow fast, as well, because it mixes the air and keeps the warm air near the snow.  But warm wind does not usually cause flooding, because it also causes evaporation of whatever it melts.  Not that flooding is actually a problem in the arctic, but I wonder if it affects melt pond formation.

[Errorr]

But seriously - Any bets on the 5-10 day forecasts getting closer to reality than they managed last year?

It depends which forecasts you mean. The forecasts published by meteorological organisations - since I doubt a major step change in processing power or methodology has been made since last year then I would expect their forecasts to have the same quality as last year (As an aside, a reduction in the quality of the long-range forecasts may be a signal of a change in the climactic system).

If you mean Friv's forecasts on the ice getting "scorched" or "blasted" - we'll never be able to tell until Friv starts using scientific terms which means the statements can be tested. It may also take Friv to realise that for ice to melt any additional (heat) energy has to be transferred to the ice (i.e. since this is mainly by conduction the heat has to get in physical contact with the ice). Showing forecasts of what is happening at 500hPa or 800hPa shows little of what is happening at ice level. Also as Crandles quite rightly points out - large temp. anomalies but with the temp.  still well below zero won't melt much ice either.

Well GFS did have a big upgrade come online this January along with some general upgrades in the surface portion. I believe they tripled the processing power and halved the grid size out to 7 days which is why the CCI Reanalyzer can now show cloud cover in the precip and cloud view since it is directly modeled instead of added through a post process analysis of the model outputs.

I also believe they finished their initialization integration with the DOD (Navy, AF) and UK Met office. In reality I believe the DOD did the work to integrat the UK for NATO purposes as the MET office feeds the UK military's model.

There were a bunch of other refinements especially in the post processing of the model data.

This is just a temporary upgrade of GFS hardware until the big upgrade comes along. It got delayed due to Lenovo buying IBM server business which greatly displeased the government and the contract was shifted over to Cray. Big part of the delay will be leveraging gpgpu tech to enhance model speed by quite a lot so I think we'll see a step change in 2016. I also believe they are working on a hexagonal model instead of a square based grid system which may make for some interesting changes.

Also the sea ice model was changed but i don't remember how. It takes a lot of testing before they are willing to upgrade the core GFS which they do once or twice a year.

GFS is more complex compared to the Euro which is based on resolution. The problem with any dynamic system is that improving accuracy beyond 7 days is proving to take a massive amount of computing power.

[epiphyte]

Not to say that many of the points made in the surface temp discussion aren't valid - but I couldn't resist mentioning that my kids and I took a walk around Lake Harriet in southwest Minneapolis this afternoon... The lake is still frozen (other than for about 10' right at the edges, where it's only a couple of feet deep) - but we were all in shirtsleeves.

Even directly downwind of the ice the air temp was well above 60F. That went all the way down to the ground, too... We actually spent half an hour or so making a sandcastle on the beach!

That's crazy.  60F is far too cold for short sleeves. 

Don't know y'er born. Sheer Luxury.

[Phil.]

I have to agree with LRC here.  I've lived in Minnesota and South Dakota for all but a couple of years of my life here and there.  It's snowed every month of the year in Minnesota.  In about half of Minnesota and almost the entirety of the other great plains states, there really is nothing to catch or reflect the sun.  Where it's flat and all there is is grass, there's nothing but white as far as the eye can see.  In the spring time, when temperatures vary wildly, I've seen the top few inches of snow melt and turn into a sheet of ice thick and solid enough you can walk on it and not fall through.  In either condition, snow or ice on the surface, temperatures well into the 50s and 60s are possible with warm air advection on strong winds.  Temperatures up to 40 are possible in almost any condition, clouds, sun, calm wind, you name it

This happened in the Northeast this winter, melt on top of snow followed by refreeze led to very melt resistant snow cover which you could walk on.  Here the best melt days were the sunny days, 40ºF and sunny seemed better than 50ºF and cloudy.

[Nightvid Cole]

Even temperatures in excess of 20 C (68 F) can occur over snowpack - for example in much of the Upper Midwest and Northeast US during the March 2012 anomalous warmth event. Along the U.S. - Canada border, several places such as Marquette, MI and Caribou, ME did this at some point from March 18-21.

That said, a large enough ice-covered body of water does chill the air, as mentioned earlier, there is nothing like trees or buildings poking above to catch the sun and heat far above the freezing point. A small lake may not do it much, but try being on the immediate downwind coast of Lake Michigan or Lake Superior when it is covered with ice...

Hudson Bay is perhaps the most extreme example of this effect. On some early summer days, the high temperatures in the surrounding land areas can easily reach 25C/77F far from the bay. But 2m temps, looking at NCEP/NCAR, are held within a few degrees of freezing over the central portion of the bay, even when the surrounding land areas are far, far warmer. GFS and NCEP/NCAR both show some area with air temps below 2 C somewhere on Hudson Bay, as long as there is ice. I have not seen a single exception, even when portions of Ontario are suffering from sweltering heat of 30-35 C!

[jbatteen]

Hudson Bay is perhaps the most extreme example of this effect. On some early summer days, the high temperatures in the surrounding land areas can easily reach 25C/77F far from the bay. But 2m temps, looking at NCEP/NCAR, are held within a few degrees of freezing over the central portion of the bay, even when the surrounding land areas are far, far warmer. GFS and NCEP/NCAR both show some area with air temps below 2 C somewhere on Hudson Bay, as long as there is ice. I have not seen a single exception, even when portions of Ontario are suffering from sweltering heat of 30-35 C!

That's pretty interesting.  Thinking back on it, I suppose my experience of snow and ice covered land may not be completely transferable to snow and ice covered water.  In my experience on the land, the snow traps air and insulates, working to limit heat transfer from top of the pack to the bottom by conduction, and leaving sublimation/evaporation and insolation at the surface interface as the primary sources of heat transfer.  Whereas a sheet of ice several thick feet has hardly any air bubbles to insulate leaving it free to conduct heat from the air on down through the ice pack and absorb a lot more heat before the surface begins to melt.  Just speculating there.

[Nightvid Cole]

Hudson Bay is perhaps the most extreme example of this effect. On some early summer days, the high temperatures in the surrounding land areas can easily reach 25C/77F far from the bay. But 2m temps, looking at NCEP/NCAR, are held within a few degrees of freezing over the central portion of the bay, even when the surrounding land areas are far, far warmer. GFS and NCEP/NCAR both show some area with air temps below 2 C somewhere on Hudson Bay, as long as there is ice. I have not seen a single exception, even when portions of Ontario are suffering from sweltering heat of 30-35 C!

That's pretty interesting.  Thinking back on it, I suppose my experience of snow and ice covered land may not be completely transferable to snow and ice covered water.  In my experience on the land, the snow traps air and insulates, working to limit heat transfer from top of the pack to the bottom by conduction, and leaving sublimation/evaporation and insolation at the surface interface as the primary sources of heat transfer.  Whereas a sheet of ice several thick feet has hardly any air bubbles to insulate leaving it free to conduct heat from the air on down through the ice pack and absorb a lot more heat before the surface begins to melt.  Just speculating there.

Yeah, though the surface of ice or snow cannot rise above freezing until it melts.

Another interesting case is Flag Island, Minnesota. The ice on Lake of the Woods typically sticks around until around April 30th or so. Over a few miles (or tens of miles, depending on wind direction) of ice-covered water, the air cools down very quickly. For example, right now it is 41 F (5 C) on Flag Island, and 52 F (11 C) in Williams, MN a few miles away from the lake. The only difference between the two is that Flag Island is surrounded by ice-covered water while Williams, MN is not!

The effect is even bigger on warmer spring days, especially when it gets over 20 C on land away from the lake. Typically as long as the lake ice is there, you can have a difference of around 10 C (18 F) between Flag Island and any city near the lake...

[Yuha]

But one thing I do know in such a situation the sunshine will be relentless and presumably the dominant surface melt factor - at the height of summer significantly stronger than the solar heating at the equator.

The effect of sunshine on melting arctic sea ice can be deceptive for a number of reasons:

1. The sun is indeed relentless in the sense that it can shine 24 hours a day and the total energy per day is higher than anywhere else, but at any given moment it is still weaker than midday sun at lower latitudes.

2. As long as the ice is covered by snow, most of the sunlight is reflected away. How much of the ice is still covered by snow in June when the sunshine is strongest can make a big difference for the whole melting season.

3. When there is no snow cover, a lot of the sunlight penetrates the ice warming the ice from the inside and even warming the water below the ice. There may not be that much immediate melt but the heat stored in the ice and the water can cause a lot of bottom melt later in the melt season.

[Neven]

...

It might be a case of people being used to what they use. I tend to look at these

from http://www.wetterzentrale.de/topkarten/fsecmeur.html

+1
IMHO the wetterzentrale pressure plot would give you the space you need. It gives info of SLP, 500 mb (which does have a lot of importance), and winds indirectly, by observing  the distance between isobars 
Then you have space for both anom and actual temps, three columns total

BTW for some reason I can only reach the third column half way. Thanks for considering these inputs

Thanks, crandles and seaicesolar, for the suggestions.

The ECMWF forecast map has always been my favourite SLP forecast map (I always use it for ASI updates), and I initially had it on this new Forecasts page as well, but there were a couple of problems:

- The ECMWF map became too small because of all the text around the map proper, making the isobar numbers unreadable.
- There are some minor differences between GFS and ECMWF, growing bigger as the forecast extends further, so the ECMWF SLP forecast map could deviate from the GFS surface wind speed map.
- Somehow the ECMWF maps didn't load properly every time (for me).
- It looks better if all the maps are from ClimateReanalyzer.

So I'm sticking with this and I'll decide whether to go for temp or temp anomaly.

[viddaloo]

2015 with a likely 128 24% bigger melt this week than 2011.

Edit: Weekly melt estimate algorithm modified to expect the average 2011 melt of the week for remaining days instead of daily 2011 melt.

[viddaloo]

The Plateau of 2015 is obviously longer and lower than that of 2012, and left earlier, meaning we're now approximately 3–4 weeks ahead of 2012 on the way down in daily extent. Albedo and other feedbacks kick in, day gets longer, 24–hours sun melts more, heats more dark open ocean.

[Rubikscube]

Attached below is the average sea ice concentration of the 11 previous SIA maximums (2012 not included because it is only available in SSMIS) together with a comparison to this years early maximum.

One can see that the pacific side stands out as way below average, while there is lots of positive anomaly on the Atlantic side of the Arctic, Labrador/St Lawrence in particular. Notice that in Okhotsk there was at maximum more ice than usual close to the northern coast, which should give a clear indication that the record low SIA in this region is at least partly due to a lack of offshore winds.

Caveat; false ice along the coast has not been removed from any of the pictures.

Click on the picture for full resolution

[slow wing]

Thanks Rubikscube, great plots!


Much of the reason for a low maximum area this season is the relative depletion of ice in the Sea of Okhotsk.

Clearly this anomaly is going to have little or no effect on the ice area minimum in the Central Arctic at the end of the melt season.

So the low maximum area  doesn't in itself suggest a low minimum.

Am I correct though that there are suggestions of widespread positive temperature anomalies in the Arctic water? Can anyone confirm or put me right? If so, would this be expected, or not, to result in more melting on the timescale of the length of the melt season? Big effect? Small effect? Thanks.

[Frivolousz21]

The reason the great plains can get that warm with snow pack obviously with a Southerly or downslope.

Is because the sun angle.

In summer arctic that daily 500w/m2 is over 24 hours.

In Spring in the great plains that 350-400w/m2 is over like 8 to 10 hours with a much higher sun angle. 

Having that Insolation come in a short period surely allows much more energy to be near surface. 

[viddaloo]

Before the weekend, 2015 looks likely to have a 42% bigger melt this week than 2011:



2006's 23–day consecutive period of being lowest in late–March and early–April has come to an abrupt end, with 2015 being lower than it yesterday, on April 2nd, splitting the lead into two separate periods of 11 days. This also means 2015's 23–day period in February and March is now the longest consecutive period of lowest sea ice extent during the coldest 5 months between late November and late April.

Depending on what happens in April and May, 2015 could very well become #2 and the Challenger here, for the title of *the* lowest for longest. A title that is of course held by 2012, a fact that also illustrates a further point, namely that 2012 was lowest on record for 83 days in a row, and not just on one day — the minimum — on September 16th.

[P-maker]

Thanks Viddaloo

Your diagrams have become much clearer now!

Looking forward to attack the 83 day long streak from back in 2012.

Cheers P

[viddaloo]

It'll be tough, but I think this year we've got all the right players onboard.

The first challenge, of course, will be to beat 2011 and 2010 in June & July.

[Nightvid Cole]

It'll be tough, but I think this year we've got all the right players onboard.

The first challenge, of course, will be to beat 2011 and 2010 in June & July.

Not really. Two-dimensional measures of the arctic sea ice have little predictive capacity for September until August.

If you are interested in September minimum (either volume or 2-d measures), you should be looking at surface melt onset and volume in June, not area or extent!

[viddaloo]

Well, opinions differ, of course, but facts say otherwise. Feel free to read up on the long–plateau hypothesis and the correlation with extreme melt seasons. In any case, I think this year we've got all the right players onboard. We'll see in June whether I'm right or not.