Environment

Claimed darkening of ice sheet could actually be down to aging satellite sensors

Greenland's ice sheet may not be getting dirtier after all
Greenland's ice sheet may not be getting dirtier after all
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Greenland's ice sheet may not be getting dirtier after all
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Greenland's ice sheet may not be getting dirtier after all

In recent years, satellite photos of Greenland's ice sheet have shown what appears to be a darkening of the ice's surface. A number of scientists have suggested that this could be due to settled soot particles from fossil fuel production and/or forest fires, and that their presence could result in accelerated melting of the ice. Now, however, researchers from Dartmouth College believe that the ice may still still be relatively clean, and that its darkness in the photos could just be due to faulty sensors on the satellites.

Ordinarily, untainted ice sheets reflect much of the sunlight that hits them back up into the sky, limiting how much solar heat is absorbed by the ice. With the Greenland ice sheet, the concern has been that dark carbon particles in the ice are allowing it to absorb more heat, speeding up the process at which the ice will ultimately melt away for good.

Led by Prof. Chris Polashenski, Dartmouth scientists analyzed dozens of snow samples taken from the ice sheet between 2012 and 2014, and compared them to samples taken over the prior 60 years. They reportedly found no significant difference in the amount of black carbon particles or mineral dust in the samples. Additionally, they ruled out algae as the culprit.

Instead, the researchers are suggesting that uncorrected degradation of sensors in NASA's MODIS (Moderate Resolution Imaging Spectroradiometer) satellites could be making the ice in the photos look darker than it actually is. Furthermore, they believe that the anomaly will likely disappear when the satellite data is reprocessed to compensate for the degradation.

They add, however, that their findings only apply to ice in the sheet's higher elevations. It still is possible that pollution or algae growth in the lower elevations could be diminishing the reflectivity of the ice.

A paper on the research was recently published in the journal Geophysical Research Letters.

Source: Dartmouth College

14 comments
Daishi
The climate change deniers are going to have a field day with this one.
Bill Bennett
@ Daishi, gawd, no kidding.
pmshah
What a load of c**p. Who is paying these jokers. Didn't anyone watch the Vice documentary on it? They did not use any kind of satellite or aerial imagery. They actually went on site and examined it closely like from a foot away. They have also recorded by time lapse photography what happens when the ice under these dark patches melt resulting in gigantic ice sheets separating from the rocks underneath and simply sliding down into the sea.
Bruce H. Anderson
If the darkening ice sheet has been part of the climate change proponents' narrative, then it is tit for tat. Bad data is bad data.
jerryd
sorry but anyone that looks at melting ice can plainly see the dirt in it is left on the surface as it melts. It can be from dust, pollution, etc blowing it or from water dirt frozen. But it'll be darker unless the ice is pure which almost never happens or stays that way. Nor will there be much in a sample from below the surface but that accumulates, concentrates as it melts. This sounds much more like a faulty scientist, not sensors.
robo
Al Gore said the science is settled, so that's the final word (for gullible easliy mislead people). We are not allowed to question anything or look deeper when it comes to global warming. Never mind that NASA is saying the ice caps are thicker and bigger than ever. NASA is a bunch of deniers.
MikeW
@Daishi: If you have any problem with others not blindly following the global cooling, errrr, global warming, errrr, climate change [from what to what?] then you only have your side to blame as they were the ones who were caught fudging the numbers and hiding the decline, not once, not just twice, not just three times, but numerous times. The shame is it is now impossible to have a rational, civil, fact based discussion as one side has shown it will do anything, even threatening using RICO laws to shut up other views. Such a discussion needs to take place but again when one side plays fast and lose with facts, multiple times, how does this discussion take place?
Don Duncan
It's not getting warmer. But if it was, that would be a net benefit, population wise, because stats show a colder climate increases deaths. Crops grow better in a warmer climate, increasing food production, but that doesn't help because governments control distribution and they distribute based on politics, i.e., special interests, regardless of the carnage. See North Korean or USSR famines for results how governments "protect".
Wolf0579
Sure, The darkening "could" be due to aging sensors. It also "could" be due to oil industry fairy dust on the objective lens of the camera. My money's on accumulated dust and soot due to accelerated melting... the original interpretation.
rpark
...seriously, is there no way to calibrate this $2 billion dollar satellite- is it still as 'dark' when they aim it at the Arctic, Alaska or a full moon, or something else with a known luminosity?
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