Northern Hemisphere Snowcover

[donsutherland1]

The week 31 figure for Northern Hemisphere snowcover was 2.071 million square kilometers. That was the lowest on record for that point in time. It is also the 2nd lowest figure on record. Only the 1968 minimum of 2.034 million square kilometers was lower.

The 2012 minimum could threaten the record, as typically there is one to perhaps two additional weeks of declining snowcover. However, even as snowcover minima have been declining, the point of the minima has also grown shorter by about a week. During the 1980-1999 period, the minimum was typically reached at 33.3 weeks (median: 33 weeks). Since 2000, the minimum has been reached at a mean point of 31.9 weeks (median: 32 weeks).

Overall, the annual minima have been running generally below the 10-year and 30-year moving averages and the 30-year moving average for minimum snowcover has fallen 11% in the past 10 years:

As a result, there has been an acceleration at the rate at which the minima have been declining. Below is a chart showing the annual minima and the 10-year and 30-year trend lines. A 10-year period is not statistically robust, but the disparity between the two trend lines hints at an accelerating rate of decline in recent years.

Given the ongoing trends coupled with the continuing rise in Arctic temperatures, it is probably more likely than not that the 2011-2020 decade will see a Northern Hemisphere snowcover minimum below 2 million square kilometers for the first time on record. Even if 2012 breaks through the 2 million square kilometer figure, it would probably be more likely than not that the second half of the decade could see at least another minimum below 2 million square kilometers given the ongoing trends.

[tacoman25]

Is there a correlating trend with max snowcover?

[donsutherland1]

Is there a correlating trend with max snowcover?

As it gets cold enough to snow across much of the Northern Hemisphere, I suspect that there's probably very little trend one way or another. I will be looking at the maximum snowcover data soon, so I'll have a better idea.

[BNAwx]

With a continued decrease in Arctic sea ice, would it be possible to have more moisture laden storms due to more open water that would aid in higher than normal snowfall amounts as we get into the colder season? Some type of negative feedback maybe?

[donsutherland1]

As it gets cold enough to snow across much of the Northern Hemisphere, I suspect that there's probably very little trend one way or another. I will be looking at the maximum snowcover data soon, so I'll have a better idea.

I ran the numbers, there's a positive 30-year trend. Maximum figures are increasing modestly. During the 1980s and 1990s, very low snowfall maxima were recorded. The 2000s saw a rebound. I'll post in more detail once I've completed my look.

[The_Global_Warmer]

I ran the numbers, there's a positive 30-year trend. Maximum figures are increasing modestly. During the 1980s and 1990s, very low snowfall maxima were recorded. The 2000s saw a rebound. I'll post in more detail once I've completed my look.

I think he is refering to a negative feedback in late Sept/Oct

[donsutherland1]

With a continued decrease in Arctic sea ice, would it be possible to have more moisture laden storms due to more open water that would aid in higher than normal snowfall amounts as we get into the colder season? Some type of negative feedback maybe?

Possibly. But the contrast between a possible trend in increased snowfall maxima and acceleration in reduced minima speaks for itself about the falling capacity for preservation of snowcover.

[Alpha5]

I would think that minimum snow cover is entirely dependent on minimum sea ice extent. In early september, all the snow up north is going to be on the sea ice, or in greenland. So, if sea ice is low, so is snowcover.

[donsutherland1]

Since 1999 when the 10-year moving average bottomed out, Northern Hemisphere snowfall maxima have been increasing, with the 10-year trend line hinting at an acceleration. Three of the past 5 years have seen maxima reach or exceed 50 million square kilometers. In contrast, the 1986-1999 period saw no 50 million square kilometer maxima.

On account of the recent rebound in snowcover maxima, the 10-year moving average has reached 49.432 million square kilometers. That's the highest figure since the 10-year period ended in 1987 (49.525 million square kilometers). Although the 30-year moving average has risen a modest +0.4% over the past 10 years, the drag is prior low snowcover maxima during the late 1980s and 1990s. The 10-year trend line, though not statistically robust, shows a sharper increase than the 30-year trend line.

If one didn't look at the minima data, one might reasonably think that the rising maxima suggest that some of the extra snowcover would last through the summer, leading to a gradual increase in the minimum figures. In other words, one might think this trend suggests a recovery of sorts is underway in the Arctic region, namely Greenland, which accounts for almost all of the summer snowcover.

The opposite is true. Even as snowcover maxima have increased at an accelerating rate, snowcover minima have declined at an accelerating rate. The snowcover minima for the 2002-2011 period and trend lines are shown below.

With 2012 currently having the second lowest snowcover figure on record and perhaps 1-2 weeks of additional declines in store, the acceleration in declining minima will be maintained on the chart that shows 2012 data.

What all this means is that conditions in the Arctic have continued to grow more hostile for preservation of snowcover. As a result, all of the buildup in winter snowcover and more is lost during the summers. A combination of factors including rising Arctic temperatures (the last two years had the warmest Arctic annual temperatures on record since at least 1880), declining Arctic sea ice, falling albedo, and increased warming of expanding open Arctic waters are likely driving this increasingly hostile environment for snowcover preservation.

[stellarfun]

Increased snow cover on the Russian side, followed by increasing areal melt of that snowcover ought to increase melt flow of Russian rivers into the Arctic, exacerbating the sea ice melt.

[tacoman25]

I would think that minimum snow cover is entirely dependent on minimum sea ice extent. In early september, all the snow up north is going to be on the sea ice, or in greenland. So, if sea ice is low, so is snowcover.

Pretty much. It's a very small percentage of the NH that has ever maintained snowcover all year around.

[tacoman25]

I ran the numbers, there's a positive 30-year trend. Maximum figures are increasing modestly. During the 1980s and 1990s, very low snowfall maxima were recorded. The 2000s saw a rebound. I'll post in more detail once I've completed my look.

Interesting. Different possible reasons for that, and different albedo/feedback effects.

The max has always been exponentially bigger than the min for snowcover, much different than sea ice extent.

[WxMidwest]

Is there an mpemba effect component to the snow or ice field as far as acceleration of area is concerned going into fall/early winter?

[donsutherland1]

In terms of North American snowcover (excluding Greenland), the following are the 5 lowest weekly figures on record:

1. 36,259 square kilometers, 2012 (week 31)

2. 41,069 square kilometers, 1984 (week 30)

3. 76,827 square kilometers, 2012 (week 30)

4. 81,568 square kilometers, 2011 (week 32)

5. 81,851 square kilometers, 1989 (weeks 31 and 32)

[The_Global_Warmer]

Spring and Summer snow cover overall like over the April-July parts has plummeted.

[bluewave]

Great thread, Don. There is a recent paper which discusses some of the points that you have brought up.

Only the abstract seems to be available ,but maybe there is a full free copy available on some science site.

http://www.agu.org/pubs/crossref/2010/2010JD014007.shtml

[Msalgado]

You would actually expect snow cover to rise in the winter in a warming world. That is how the current theory behind the building of ice sheets being tied to summer insolation in the northern hemisphere works. As the winters warm, you get an increase of water vapor in the atmosphere and more snow. At the same time, you are experiencing cooler Summers so there is less melt and you get a net accumulation.

Of course that is not the case here, but we are seeing that a warmer winter might be increasing the amount of snow cover as would be expected.

[donsutherland1]

You would actually expect snow cover to rise in the winter in a warming world. That is how the current theory behind the building of ice sheets being tied to summer insolation in the northern hemisphere works. As the winters warm, you get an increase of water vapor in the atmosphere and more snow. At the same time, you are experiencing cooler Summers so there is less melt and you get a net accumulation.

Of course that is not the case here, but we are seeing that a warmer winter might be increasing the amount of snow cover as would be expected.

It is interesting how this is playing out. The warming winters are witnessing more expansive snowcover, but the magnitude of the overall warming is sufficiently large that all of that extra snowcover and more is melting during the summers.

[donsutherland1]

FWIW, a newly published paper discusses an increase in poleward atmospheric moisture transport.

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1631.html

Perhaps this increased moisture helps explain expanding winter snowcover maxima in the Northern Hemisphere.

[tacoman25]

You would actually expect snow cover to rise in the winter in a warming world. That is how the current theory behind the building of ice sheets being tied to summer insolation in the northern hemisphere works. As the winters warm, you get an increase of water vapor in the atmosphere and more snow. At the same time, you are experiencing cooler Summers so there is less melt and you get a net accumulation.

Of course that is not the case here, but we are seeing that a warmer winter might be increasing the amount of snow cover as would be expected.

Wouldn't greater snowcover in winter/early spring tend to result in cooler late winters/early springs due to albedo effects?

[The_Global_Warmer]

Wouldn't greater snow-cover in winter/early spring tend to result in cooler late winters/early springs due to albedo effects?

Yeah it will depend on other things. The snow for instance doesn't really fall apart until April/May. Which means it falls apart when the solar insolation comes like a train.

So the main place snow is not holding on is 60-82N. This is also the place solar radiation sky rockets during April/May. It fit's the bill by basic physic's and by correlation, there is nearly no doubt on this part of it IMO. I think natural factors will play a large role in snow cover in Spring/Summer as well as GHG forcing.

But albedo in this sense isn't as strong as others. The Winter going into Spring snow-pack is very dependent historically on natural varition. We can see this just by glancing at this map. Probably a lot of AMO in there and maybe some background warming. But in March before the Solar Dance the snow cover is still mostly pattern based and natural variance.

Then April comes and every year in the recent times is far lower than March, except for a few. We can still the 1980s being lower snow my guess is +AMO from I believe late 87 to 91 or so, then it was interrupted and now it's come back stronger again obviously, the PDO would have been positive or neutral back then. And we go to May.

Now the GHG signal and amplification is showing up. May snowcover is now in the high latitudes where not only long 12, 15, 18 hour days of decent solar altitude but very consistent is now pumping out more solar radiation than in warmer lower latitudes by May. That means the down-welling Greenhouse effect will be amplified.

Co2 is steadily rising more and more. While it may not have a direct effect on the global temperature regime that is lets say as pronounced as somethings. But we know now at 400PPM in the arctic that with historical data like ice cores we will be seeing a stronger and stronger direct forcing. And imagine 60-82N gets all of it's solar insolation in far shorter period that South of there, so this effect is amplified and get's stronger as the GHG concentrations go up.

On top of Co2, Methane is not only going up again(yes it's slow attm, which is good.) but it's also at quite a bit higher concentrations in the 60-90N region. Which again is not only another Green House Effect, it's amplified in the arctic region because higher concentrations are in this region.

Then we get to June and all hell breaks loose. Ok, it is definitely not like that, haha. But most years start to level off and reach more of a median with what there patterns and circumstances left. Recent years show a wild signal though that looks like a GHG + AMO signal. Probably a bit more GHG induced at first but this will also effect the AMO. But even if the AMO isn't big factor in this, the PDO could be, but that would tend to bring more snow to the Eastern Asian side(Eastern SIberia, I would think, and maybe Alaska side.) EIther way this brings us full circle about albedo feedback.

If we take out GHG forcing and make it go back to 300PPM tomorrow. By next Spring when snow falls, this GHG feedback or amplification would be gone and while maybe we see a negative snow cover year it won't be like the recent ones and it will be pattern driven because in that situation albedo feedback from snow probably has enough of a cooling effect or self preservation effect to slow down the speed of the annual snow melt.

with GHG forcing now becoming strong enough it can directly play a role in these things. So it has a large role in melting ice and snow, RELATIVELY LARGE, but it doesn't have the same direct effect on temps.

I am sure someone can do some math on energy to raise temps and energy to melt snow or ice. So eventually with the GHG forcings behind it the snow albedo effect ends up being a positive feedback for warming instead of cooling.

[PhillipS]

Great post, Friv. One question I had that you may have some insight on. I read recently that the low shrubby plants in the arctic tundra are growing taller with the increased warming (here's a Huffington Post article on this). My question is - do you think the taller vegetation will affect the snowcover trends? I would think that taller vegetation would reinforce the trend because early snowfalls would settle through the leaves and give less of an albedo change. And the taller plants would catch light from low sun angles instead of reflecting it. Of course, the limiting factor is that once the sun is down albedo is less of a factor.

[Vergent]

Great post Friv, good research.

Its worst than PIOMAS trends. The wattage is enormous. around 2.1 tera watts.

[WeatherRusty]

When speaking to a strengthening greenhouse effect in the arctic, this is in itself a feedback to a generalized global warming. A feature of global warming is arctic amplification, where the arctic warms at a rate surpassing the average for the globe as a whole.

This is partly the result of albedo feedback as longer lasting, greater areal exposed open water absorbs solar energy at an increasing rate over that of an ice surface during summer.

The stronger impact results from increasing atmospheric water vapor which grows exponentially with increasing temperature. This promotes cloudiness which in the arctic produces a net warming effect of the surface due to the long arctic night. Clouds in the arctic thus enhance the greenhouse effect of downwelling longwave radiation. The water vapor increase over the open water increases the greenhouse effect as it does anywhere else on the planet.

This paper claims that a quadrupling of CO2 from pre-industrial levels of 280ppm would trigger an ice free arctic year round. This fits well with the Cretaceous Period condition with CO2 levels over 1000ppm and no permanent arctic sea ice.

Processes and impacts of Arctic amplification

Would this be better made a new thread? Any interest?

[bluewave]

New paper just out on this topic is getting some attention in the news.

http://www.agu.org/pubs/crossref/pip/2012GL053387.shtml

http://www.npr.org/2012/09/24/161701420/as-arctic-ice-melts-so-does-the-snow-and-quickly?sc=tw

Spring snow cover extent reductions in the 2008-2012 period exceeding climate model projections

Key Points

• N. Hemisphere spring snow cover extent reductions since 1967 are significant
  
• Rate of June snow loss exceeds the rate of September sea ice loss (1979-2011)
  
• Snow reductions since 2005 exceed an ensemble of CMIP5 simulations
  

Authors:

Chris Derksen

Ross Brown

Analysis of Northern Hemisphere spring terrestrial snow cover extent (SCE) from the NOAA snow chart Climate Data Record (CDR) for the April to June period (when snow cover is mainly located over the Arctic) has revealed statistically significant reductions in May and June SCE. Successive records for the lowest June SCE have been set each year for Eurasia since 2008, and in 4 of the past 5 years for North America. The rate of loss of June snow cover extent since 1979 (-21.5% decade-1) is greater than the loss of September sea ice extent (-10.8% decade-1) over the same period. Analysis of Coupled Model Intercomparison Project Phase 5 (CMIP5) model output shows the marked reductions in June SCE observed since 2005 fall below the zone of model consensus defined by +/-1 standard deviation from the multi-model ensemble mean.

Received 30 July 2012; accepted 9 September 2012.

Citation: Derksen, C. and R. Brown (2012), Spring snow cover extent reductions in the 2008-2012 period exceeding climate model projections, Geophys. Res. Lett., doi:10.1029/2012GL053387, in press.

[Midlo Snow Maker]

it's been awhile but we are back above normal snowcover now

[tacoman25]

it's been awhile but we are back above normal snowcover now

How does this compare with recent years?

[CoastalWx]

Southern Canada and NW Russia about to get their snowpack on.

[tacoman25]

How does this compare with recent years?

No one knows this? I am curious if other recent years have seen the snow cover recover this quickly to above normal.

[ORH_wxman]

No one knows this? I am curious if other recent years have seen the snow cover recover this quickly to above normal.

This year is doing very well right now...the last year that seemed to be this robust at this point was 2006 (didn't turn out so well for winter though) followed by 2002.

2009 absolutely exploded though between now and the end of the month. At this point though, 2009 wasn't at the levels of this year...but the next week or so it went gangbusters. Really after 10/22/09.

This year looks like it could go ganbusters too over the next 10 days, but we'll just have to wait and see. 2009 was pretty special in that regard...this year's pattern looks favorable, but it doesn't guarantee it will go nuts.