Melt extent in Greenland was well above average in 2014, tying for the 7th highest extent in the 35-year satellite record.The figure below showss the surface melt day anomaly for the last four years, the number of melt days compared to the average number of melt days. You can see the pattern hasn't been good. The number of melt days is increasing for the low-altitudes regions.
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| Source: NSIDC |
We'll say 2012 was an abnormality and discount that one. Let's hope we don't see any more years like that one. That still leaves a clear pattern of an increased number of melt days these last few years compared to the long-term average number of melt days.Comparing the seasonal progression of the four most recent years, the recent tendency for greater-than-average melt extent is apparent, as are the rapid variations in melt extent mid-year.
In case you are plan on objecting on the basis the interior is experiencing a normal melt routine, consider these facts:
- As the ice melts the higher altitudes get lower every year, increasing the number of melt days;
- As the coastal ice melts, the interior ice will push out and spread, again bringing the higher altitude ice down;
- As the melt season increases it results in dark pools of water sitting on the surface for longer periods of time where they absorb more sunlight than the reflective ice, increasing the amount of melting.
In the paper, The pattern of anthropogenic signal emergence in Greenland Ice Sheet surface mass balance, published in Geophysical Research Letters last August, researchers concluded human-driven climate change is increasingly responsible for current trends in Greenland Ice Sheet melt and accumulation. They also concluded human activity will dominate further melt and accumulation pattern throughout the 21st century.
In case you still think the Greenland Ice Sheet is recovering, take a look at this graph:
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| Source: Polar Portal |
By the way, the NSIDC report also said the top eight melt extent years have all occurred since
2002.
Here is one showing snow pack changes for the western U.S. Some places increased while about 75% of the places experienced a decrease. There was an over 14% decline since 1950.
ReplyDeletehttp://www.epa.gov/climatechange/science/indicators/snow-ice/snowpack.html
Here is a reference on Himalaya snow pact that reports the decline between 2000 and 2010 was about -1.25% per year and was similar to the trend from the 1990s.
http://www.the-cryosphere-discuss.net/5/755/2011/tcd-5-755-2011.pdf
Himalaya? The glacier up there has been subliming for decades; (not melting, because the temperature never gets above freezing, I'm sure you know that, but, just restating that for the casual reader who happens by... ) So, you're right on that one, but the cause isn't global, nor from greenhouse gases, but (probably) land-use changes (deforestation, locally)...
ReplyDeleteClaims made with no evidence are useless. You are incorrect about the subliming too.
ReplyDeleteJust for the casual reader who happens by.... Sublimation is when water goes from the solid state straight to the vapor state without going through the liquid state. If that were the case, then explain why there is so much liquid runoff from the Himalayas?
ReplyDeleteIt is true that it never gets above freezing - IF you get high enough. What is being observed is the "high enough" point is getting higher and higher. If the average temp is -15 C and it warms to -10 C, there has been warming but it is still below freezing. But, if it warms from -3 C to +2 C there has been warming and that region is now above freezing and will experience melting.
It is very easy to see this is what is happening. The snowline keeps getting higher, glaciers are retreating and the wintertime runoff is increasing.
There has been sublimation all along and it is continuing. But, what has changed to account for all of those changes we are observing?
Snowpack in Gothic, Colorado, as reported by
ReplyDeleteInouye, David W., et al. "Climate change is affecting altitudinal migrants and hibernating species.” Proceedings of the National Academy of Sciences 97.4 (2000): 1630-1633.
http://www.pnas.org/content/97/4/1630.full
”… At our study site, the beginning of the growing season is controlled by melting of the previous winter's snowpack. Despite a trend for warmer spring temperatures the average date of snowmelt has not changed, ... significantly over the past 25 years.”
”Calendar date of the beginning of the growing season at high altitude in the Colorado Rocky Mountains is variable but has not changed significantly over the past 25 years.”
”The trends we report for earlier formation of permanent snowpack and for a longer period of snow cover...”
Disagrees with your:
http://www.epa.gov/climatechange/science/indicators/snow-ice/snowpack.html
which is really a digestion of Mote, Philip W., et al. "Declining mountain snowpack in western North America." (2005). American Meteorological Society (BAMS)
http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/28018/MotePhilipW.CEOAS.DecliningMountainSnowpack.pdf?sequence=1
...in that "the trend line is steadily decreasing" just isn't so, according to Inouye. The distribution is more random, so it depends on when the start and end time periods of the study.
Yeah, blew that one... was thinking of Kilimanjaro.
ReplyDeleteThis graphic seems to have disappeared...
ReplyDeleteMote, Philip W., et al. 2005 shows observations of a 20+ year track record of California's incredibly stable snowpack... 1980-2000
ReplyDeleteMote, Philip W., et al. "Declining mountain snowpack in western North America." (2005). (BAMS)
ReplyDeletehttp://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/28018/MotePhilipW.CEOAS.DecliningMountainSnowpack.pdf?sequence=1
"trend line is steadily decreasing" does not apply.
Mote, Philip W., et al. 2005 shows observations of a thin line, with not even a one-centimeter deviation, 1950-2000. I suppose that one year, it is here, and the next year, over there... aggregate all of California, and there is no steady decline.
ReplyDeleteI blew this one, thinking of Kilimanjaro.
ReplyDeleteI am not sure what point you are trying to make with these comments. You are not very clear. It actually seems at times you are trying to make the case snowpack is decreasing and other times that it isn't. I think the best you have done is to demonstrate you can pick an isolated area for a specific time period and get the answer you want. That is a double edge sword and I could look at a specific mountain and a limited time period and get any result I want (for instance, see: http://news.nationalgeographic.com/news/2015/01/150130-snowpack-snow-drought-california-environment-united-states/). But, that isn't science. We want to know what is happening across the whole planet. The topic is "global" warming, not "this particular mountain" warming.
ReplyDeleteWhen the study is done scientifically the answer is: snowpack worldwide is decreasing and it is doing it an alarming rate. Take a look at these references. These are just a few. There are, literally thousands of references showing snowpack around the world is declining.:
http://www.nrmsc.usgs.gov/northamersnowpack
In western North America snowpack has declined in recent decades, and further losses are projected
through the 21st century. Here we evaluate the uniqueness of recent declines using snowpack reconstructions from 66 tree-ring chronologies in key runoff generating areas of the Colorado, Columbia and Missouri River drainages. Over the past millennium, late-20th century snowpack reductions are almost unprecedented in magnitude across the northern Rocky mountains, and in their north-south synchrony across the cordillera. Both the snowpack declines and their synchrony result from unparalleled springtime warming due to positive reinforcement of the anthropogenic warming by decadal variability.
The increasing role of warming on large-scale snowpack variability and trends foreshadows fundamental impacts on streamflow and water supplies across the western USA.
https://fortress.wa.gov/ecy/publications/publications/0711016.pdf
The average mountain snow pack in the North Cascades (critical to summer stream-flows) has declined at 73 percent of mountain sites studied.
Spring runoff is occurring earlier each year.
Stream flows are peaking earlier in the year in watersheds throughout the state, including the Columbia Basin.
Mountain glaciers in the North Cascades have lost 18 to 32 percent of their total volume since 1983.
Here are some more:
http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-86-1-39
http://www.scientificamerican.com/article/rapid-decline-mountain-snowpack-bad-new-western-us-rivers/
http://www.doi.gov/news/pressreleases/USGS-Study-Finds-Recent-Snowpack-Declines-in-the-Rocky-Mountains-Unusual-Compared-to-Past-Few-Centuries.cfm
http://onlinelibrary.wiley.com/doi/10.1002/grl.50424/abstract
http://www.realclimate.org/index.php/archives/2007/03/pnw-snowpack/
http://www.worldclimatereport.com/index.php/2010/10/08/tibetan-snowpack-decreasing/
http://picturethis.pnl.gov/picturet.nsf/by+id/AMER-6PWV.V