The melt extent algorithm used by Greenland Ice Sheet Today has been overestimating the melt extent, and as a result, daily images posted on this site in February and March may have indicated melt where none occurred.
This makes you wonder what other kinds of issues remain undetected in the satellite data. NSIDC has had to issue corrections in the past, when it was pointed out that their data and reality didn’t match. – Anthony
The algorithm for the Greenland Ice Sheet Today daily melt extent has been revised to account for unusually warm winter snow layers and residual meltwater deep in the snow. Meltwater from last summer’s intense melt season did not completely re-freeze through at least mid December. The adjusted algorithm shows greatly reduced melt extent for early 2013. This much lower extent is more consistent with available weather and climate records.
Melt extent and distribution
Figure 1. These images show cumulative melt extent before the algorithm correction (left) and after the correction (right). A few areas indicating one to two days of melting in southeast Greenland remain in the revised map. The red dot shows the location of the Danish AWS. Credit: National Snow and Ice Data Center – Click for hires imageAs shown in Figure 1, the adjustment to the algorithm resulted in fewer melt days than previously indicated. The revised image at right shows new surface melting in 2013 in a few small areas along the central southeastern Greenland coast, within the region of earlier spurious melt signals but greatly reduced.
Conditions in context
Figure 2. This image shows air temperature anomaly for Greenland for the period December 2012 to February 2013. Reds and oranges indicate higher than average air temperatures. The temperatures shown are at approximately 1,500 meters (5,000 feet) in altitude, appropriate for coastal Greenland regions. However, central Greenland is above this altitude, and values shown there do not represent the true surface conditions well. Credit: National Snow and Ice Data Center courtesy NOAA ESRL Physical Sciences DivisionTemperatures in Greenland have been higher than average this winter, with air temperatures near the coast averaging 2.0 to 3.5 degrees Celsius (4 to 6 degrees Fahrenheit) warmer than the 1981 to 2010 average. This has in part been a result of the persistent circulation pattern for the Arctic this winter, characterized by a negative Arctic Oscillation (AO). The AO is a measure of the intensity of the general pattern of low pressure over the northern high latitudes. A negative AO indicates higher-than-average pressures near the North Pole, allowing more frequent southward cold air outbreaks, and more intrusions of warm air masses from higher temperature areas. Despite these anomalously high temperatures along the Greenland coast, temperatures were not high enough to result in melting.
Adjusted algorithm and melt images
Figure 3. This plot shows surface air temperature at a PROMICE on-ice Automated Weather Station (AWS) near the southeastern Greenland ice sheet edge for early 2013. Temperatures did not exceed freezing at this site. Data from PROMICE were provided by the Geological Survey of Denmark and Greenland (GEUS) and are freely available. Credit: National Snow and Ice Data Center and J. Box, Geological Survey of Denmark and GreenlandThe melt extent algorithm used by Greenland Ice Sheet Today has been overestimating the melt extent, and as a result, daily images posted on this site in February and March may have indicated melt where none occurred. While the algorithm was indicating some coastal melt in February and early March, a comparison with weather data for Nuuk (the Greenland capital city, located along the southwest of the island) and data from the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) suggested these might be spurious melt readings. The local Automated Weather Station (AWS) data from a glacier along the southeastern coast (the Mittivakkat glacier AWS, shown by a red dot in Figure 1; data in Figure 3) indicate that the air temperature did not rise to the melting point (0 degrees Celsius, or 32 degrees Fahrenheit) in February or early March.
Figure 4. A model of the snowpack conditions indicates residual liquid water in the deep snowpack in southeastern Greenland. Credit: National Snow and Ice Data Center and X. Fettweis, Université de Liège, BelgiumDuring this period, starting around mid-February in southeast Greenland, the brightness temperatures in the upper few meters of the snowpack were 2 to 10 degrees Celsius (4 to 18 degrees Fahrenheit) higher than those observed during any other year in the 34-year record (1979 to 2012). While surface melt is not unprecedented in Greenland near the coast in February and March, the totals posted prior to March 14 were a result of these unusual snow temperature conditions, and not ongoing surface melt. This winter has seen unusually warm snow at depth on the ice sheet, following the intense melting that occurred last summer.
The melt detection method, based on passive microwave emissions, is primarily sensitive to near-surface conditions, but has some input from the snowpack down several meters (10 to 20 feet). Heavy snow fell during the relatively warm winter, burying and insulating deeper snow. This contributed to anomalously high temperatures for the uppermost layers of snow this winter. Additionally, models based on snowpack properties suggested that some 2012 meltwater remained unfrozen at 5 meters depth (approximately 16 feet) in mid-December. The model results are consistent with observations from JAXA’s AMSR-2 sensor.
The algorithm was adjusted by combining the trend of observed brightness temperatures with a model of the expected microwave emission in the channels used for melt detection (the SSM/I sensor’s 37 GHz Horizontal polarization channel). This adjustment is generally performed every year in March to calibrate the melt detection thresholds. However, because of the unusual condition of the snowpack, the adjustment needed to be made much earlier than ever before.
Further information
Fettweis, X., M. Tedesco, M. van den Broeke, and J. Ettema, 2011. Melting trends over the Greenland ice sheet (1958-2009) from spaceborne microwave data and regional climate models. The Cryosphere 5, 359-375, doi: 10.5194/tc-5-359-2011.
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D.B. Stealey
March 23, 2013 4:12 am
Sure, barry. But they never seem to underestimate the ice melt, do they? Seems like they’re covering their butts here, before an inconvenient fact comes to light. Now that the P.R. damage is done, they come back and say, “Oops.”
Alarmists like barry are nothing if not credulous. *eyeroll*
Marcos
March 23, 2013 4:59 am
Anthony,
Didnt NSIDC say that they were going to change their sea ice anomaly period from 1979-2000 to something including more recent years? iirc, they said last year that the work was done and they were just waiting for the right time (whatever that means)
@Marcos, yes they did. I’ll look up that conversation.
jonny old boy
March 23, 2013 5:05 am
In late spring of 2012 the very same organisation was telling a man in North East Canada ( who was looking out to sea as far as he could see from his living room window, staring at solid sea-ice with no liquid water anywhere to be seen ) that there was indeed no sea ice at all and he could merrily hop in his boat and sail away somewhere nice…..I actually menioned this on Mann’s facebooks site, and was summarily banned from the site….
barry
March 23, 2013 5:09 am
Sure, barry. But they never seem to underestimate the ice melt, do they?
It doesn’t matter what they do, people will complain. If the Met Office say they had previously been underestimating temps, then the peanut gallery will call foul on the new, warmer record. (“Why are adjustments always up?!?”) If it had gone the other way, the peanut gallery would be saying what you’re saying about NSIDC. (“Why do they never seem to underestimate warming?!?”)
There’s no consistency to these complaints – they’re contradictory. And predictable and boring. Any adjustment, any change of any sort is an opportunity to for people to grind their axes. Any change is an opportunity to suggest a conspiracy, malfeasance or whatever. That’s the only consistent part of it. [Formatting fixed -w.]
jayhd
March 23, 2013 7:07 am
Numerobis, Barry and others – You seem to be missing the point of the criticism, at least my criticism. NSIDC and Greenland Ice Sheet Today are publishing, for public consumption mind you, maps and articles on the, for lack of a better way of putting it, the demise of the Greenland glaciers. These maps and articles are based on satellite images and computer models. Many of the maps and articles have a decidedly alarmist slant to them. These are then taken up by the CAGW/Climate Change advocates in the mainstream media and in academia. The big problem I have with all this is that all these maps and articles are based on data gathered by satellite and fed into computer models with little or no actual on the ground work to validate anything. For example, the correction highlighted in the article we are commenting on was for February and March of this year. But I ask the question, what about January? Or any of the earlier months? As Athony writes in his opening paragraph “This makes you wonder what other kinds of issues remain undetected in the satellite data”. Validating computer interpretations of satellite data is a very tricky affair, especially if the people doing the programming and validating have little or no real field experience. They tend to go on assumption, not observation. It is my opinion that too many of the people working in the “climate science” field overly rely on the accuracy of their computer models, to the detriment of real scientific field work.
By the way, besides the problems with GISS I noted in an earlier post, I have also had real world experience while in the military with regards to the limitations of satellite imagery and its interpretation by intelligence “experts”. These experiences were, for the most part, somewhat unpleasant.
barry
March 23, 2013 7:41 am
It is my opinion that too many of the people working in the “climate science” field overly rely on the accuracy of their computer models, to the detriment of real scientific field work.
How many field trips have been done over the last 3 years?
I got 895 hits in google scholar googling ‘Greenland mass balance fieldwork’, setting the parameters 2011 to 2013.
There will be a lot of double-ups, but on what information is your opinion based? Do you think there should be more funding for trips to the Greenland ice? What well-considered solutions do you have in mind?
barry
March 23, 2013 7:46 am
Aye, but you could imagine if there was a lot of money being spent on field trips to Greenland.
“They have perfectly good satellites paid for by our tax dollars that can see the whole area. Excursions to look at ice in a few locations are a waste of money.”
Peanuts, anyone?
john robertson
March 23, 2013 10:35 am
What climatologists engaging in exaggerations?
Never happens, must be unprecedented since yesterday.
The art of climatology is coming to resemble one of the oldest arts, more each day.
Talespinning however is a respected and lucrative art.
With the extended very cold winter into spring in both Eurasia (they had to scrape off a Northern Ireland soccer field for a FIFA match two days ago) and North America, temps still -25C over much of the Greenland Sheet in the first few days of spring and a rapidly rebounded arctic ice sheet – still presssing against the north shore of Hokkaido, Japan- water may be scarce on the Greenland ice this summer.
Also, having had a satellite-era record high Antarctic ice sheet extent in the SH winter followed by a rebound in one month to a positive anomaly of almost 1 million square km, look to cold weather this coming SH winter in South America, Australia, New Zealand and South Africa. I predicted last fall a particularly cold NH winter partly because of the record ice in Antarctica in SH winter (and partly because of subdued non-development of El Nino and the likely bending of the global flat trend to a decline). Commonly an especially cold winter in the SH presages one to follow in the NH (and vice versa until this zig-zag swing dampens down). Looking at the rapid ice growth in Antarctica at present, sets the stage for a new record Antarctic ice extent, a cold winter in SH, followed by another very cold NH winter. Any bets? Eww, it must be tough to be a burning-in-hell CO2 warming maven these days.
Good analysis, Gary. Add early albedo effects in northern (and later, all of) Asia resulting from open Arctic waters, and your picture, with record SCE, is relatively complete!
barry says:
March 23, 2013 at 5:09 am
One of the problems is that if you are an analyst who has a strong belief in the catastrophic degree of global warming, your analysis is going to go as far to the extreme as is decently possible – the data gives you a range to choose from. I pointed out about 4 or 5 years ago to theweathernetwork.com that I had made better forecasts than they for a period of 3 months by using their forecasts and trimming the heat off by about a degree. I emailed this to them.and got no reply. Today, I note thru late winter and this cold spring, their 2 week forecasts trend always starts below normal where it is at, but manages in the final week to climb up to above normal. Why? Because, gee, it must balance out, mustn’t it in these times of CAGW. I think a study of the meteorological data of HadCrut, GISS, etc. by totally independent specialists would have given cooler temperature forecasts these past 15 years or so. It would be a good exercise to give data without identifying the period it came from and have them make a forecast to compare with the real one – maybe someone should try this – Bastardi maybe? You may also have noticed barry that they have added things on to the sea level data to make for more sea level rise, etc.
Sure, barry. But they never seem to underestimate the ice melt, do they? Seems like they’re covering their butts here, before an inconvenient fact comes to light. Now that the P.R. damage is done, they come back and say, “Oops.”
Alarmists like barry are nothing if not credulous. *eyeroll*
Anthony,
Didnt NSIDC say that they were going to change their sea ice anomaly period from 1979-2000 to something including more recent years? iirc, they said last year that the work was done and they were just waiting for the right time (whatever that means)
@Marcos, yes they did. I’ll look up that conversation.
In late spring of 2012 the very same organisation was telling a man in North East Canada ( who was looking out to sea as far as he could see from his living room window, staring at solid sea-ice with no liquid water anywhere to be seen ) that there was indeed no sea ice at all and he could merrily hop in his boat and sail away somewhere nice…..I actually menioned this on Mann’s facebooks site, and was summarily banned from the site….
It doesn’t matter what they do, people will complain. If the Met Office say they had previously been underestimating temps, then the peanut gallery will call foul on the new, warmer record. (“Why are adjustments always up?!?”) If it had gone the other way, the peanut gallery would be saying what you’re saying about NSIDC. (“Why do they never seem to underestimate warming?!?”)
There’s no consistency to these complaints – they’re contradictory. And predictable and boring. Any adjustment, any change of any sort is an opportunity to for people to grind their axes. Any change is an opportunity to suggest a conspiracy, malfeasance or whatever. That’s the only consistent part of it.
[Formatting fixed -w.]
Numerobis, Barry and others – You seem to be missing the point of the criticism, at least my criticism. NSIDC and Greenland Ice Sheet Today are publishing, for public consumption mind you, maps and articles on the, for lack of a better way of putting it, the demise of the Greenland glaciers. These maps and articles are based on satellite images and computer models. Many of the maps and articles have a decidedly alarmist slant to them. These are then taken up by the CAGW/Climate Change advocates in the mainstream media and in academia. The big problem I have with all this is that all these maps and articles are based on data gathered by satellite and fed into computer models with little or no actual on the ground work to validate anything. For example, the correction highlighted in the article we are commenting on was for February and March of this year. But I ask the question, what about January? Or any of the earlier months? As Athony writes in his opening paragraph “This makes you wonder what other kinds of issues remain undetected in the satellite data”. Validating computer interpretations of satellite data is a very tricky affair, especially if the people doing the programming and validating have little or no real field experience. They tend to go on assumption, not observation. It is my opinion that too many of the people working in the “climate science” field overly rely on the accuracy of their computer models, to the detriment of real scientific field work.
By the way, besides the problems with GISS I noted in an earlier post, I have also had real world experience while in the military with regards to the limitations of satellite imagery and its interpretation by intelligence “experts”. These experiences were, for the most part, somewhat unpleasant.
How many field trips have been done over the last 3 years?
I got 895 hits in google scholar googling ‘Greenland mass balance fieldwork’, setting the parameters 2011 to 2013.
There will be a lot of double-ups, but on what information is your opinion based? Do you think there should be more funding for trips to the Greenland ice? What well-considered solutions do you have in mind?
Aye, but you could imagine if there was a lot of money being spent on field trips to Greenland.
“They have perfectly good satellites paid for by our tax dollars that can see the whole area. Excursions to look at ice in a few locations are a waste of money.”
Peanuts, anyone?
What climatologists engaging in exaggerations?
Never happens, must be unprecedented since yesterday.
The art of climatology is coming to resemble one of the oldest arts, more each day.
Talespinning however is a respected and lucrative art.
With the extended very cold winter into spring in both Eurasia (they had to scrape off a Northern Ireland soccer field for a FIFA match two days ago) and North America, temps still -25C over much of the Greenland Sheet in the first few days of spring and a rapidly rebounded arctic ice sheet – still presssing against the north shore of Hokkaido, Japan- water may be scarce on the Greenland ice this summer.
Also, having had a satellite-era record high Antarctic ice sheet extent in the SH winter followed by a rebound in one month to a positive anomaly of almost 1 million square km, look to cold weather this coming SH winter in South America, Australia, New Zealand and South Africa. I predicted last fall a particularly cold NH winter partly because of the record ice in Antarctica in SH winter (and partly because of subdued non-development of El Nino and the likely bending of the global flat trend to a decline). Commonly an especially cold winter in the SH presages one to follow in the NH (and vice versa until this zig-zag swing dampens down). Looking at the rapid ice growth in Antarctica at present, sets the stage for a new record Antarctic ice extent, a cold winter in SH, followed by another very cold NH winter. Any bets? Eww, it must be tough to be a burning-in-hell CO2 warming maven these days.
Good analysis, Gary. Add early albedo effects in northern (and later, all of) Asia resulting from open Arctic waters, and your picture, with record SCE, is relatively complete!
barry says:
March 23, 2013 at 5:09 am
One of the problems is that if you are an analyst who has a strong belief in the catastrophic degree of global warming, your analysis is going to go as far to the extreme as is decently possible – the data gives you a range to choose from. I pointed out about 4 or 5 years ago to theweathernetwork.com that I had made better forecasts than they for a period of 3 months by using their forecasts and trimming the heat off by about a degree. I emailed this to them.and got no reply. Today, I note thru late winter and this cold spring, their 2 week forecasts trend always starts below normal where it is at, but manages in the final week to climb up to above normal. Why? Because, gee, it must balance out, mustn’t it in these times of CAGW. I think a study of the meteorological data of HadCrut, GISS, etc. by totally independent specialists would have given cooler temperature forecasts these past 15 years or so. It would be a good exercise to give data without identifying the period it came from and have them make a forecast to compare with the real one – maybe someone should try this – Bastardi maybe? You may also have noticed barry that they have added things on to the sea level data to make for more sea level rise, etc.