Arguments
Has Arctic sea ice returned to normal?
What the science says...
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Thick arctic sea ice is in rapid retreat. |
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Climate Myth...
Arctic sea ice has recovered
"Those who have been following NSIDC and JAXA sea ice plots have noted that this has been an extraordinary year so far, with Arctic sea ice hitting the “normal” line on some datasets. ...
As of today, JAXA shows that we have more ice than any time on this date for the past 8 years of Aqua satellite measurement for this AMSRE dataset." (Anthony Watts, 22 April 2010)
Discussions about the amount of sea ice in the Arctic often confuse two very different measures of how much ice there is. One measure is sea-ice extent which, as the name implies, is a measure of coverage of the ocean where ice covers 15% or more of the surface. It is a two-dimensional measurement; extent does not tell us how thick the ice is. The other measure of Arctic ice, using all three dimensions, is volume, the measure of how much ice there really is.
Sea-ice consists of first-year ice, which is thin, and older ice which has accumulated volume, called multi-year ice. Multi-year ice is very important because it makes up most of the volume of ice at the North Pole. Volume is also the important measure when it comes to climate change, because it is the volume of the ice – the sheer amount of the stuff – that science is concerned about, rather than how much of the sea is covered in a thin layer of ice*.
Over time, sea ice reflects the fast-changing circumstances of weather. It is driven principally by changes in surface temperature, forming and melting according to the seasons, the winds, cloud cover and ocean currents. In 2010, for example, sea ice extent recovered dramatically in March, only to melt again by May.
Sea-ice is subject to powerful short-term effects so while we can't conclude anything about the health of the ice from just a few years' data, an obvious trend emerges over the space of a decade or more, showing a decrease of about 5% of average sea-ice cover per decade.
Source: Rayner et al. (2004), updated
Where has the thick ice gone?
When we consider the multi-year ice and look at the various measurements of it, we see a steep decline in this thick ice. As you might imagine, thick ice takes a lot more heat to melt, so the fact that it is disappearing so fast is of great concern.
Source: Polar Science Centre, University of Washington
It is clear from the various data sets, terrestrial and satellite, that both the sea ice extent and multi-year ice volume are reducing. Sea ice extent recovered slightly during the Arctic winters of 2008-09, but the full extent of annual ice reduction or gain is seen in September of each year, at the end of the Arctic summer. The volume of multi-year ice has not recovered at all, and is showing a steeply negative trend.
* Footnote: Although a thin layer of ice doesn’t tell us much about the overall state of ice loss at the Arctic, it does tell us a great deal about Albedo, the property of ice to reflect heat back into space. When the sea ice diminishes, more heat passes into the oceans. That heat melts the thick ice and speeds up the melting of thinner sea ice, which in turns allows more heat to accumulate in the oceans. This is an example of a positive feedback.
Basic rebuttal written by GPWayne
Update July 2015:
Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial
This rebuttal was updated by Judith Matz on September 13, 2021 to replace broken links. The updates are a result of our call for help published in May 2021.
Last updated on 14 July 2015 by MichaelK. View Archives
No, No, everything's OK with Arctic ice (kidding). Steven Goddard has a plot on his site showing that recently, there was the "Most Ice Gain Ever Recorded". What the plot seems to show is sea ice area change from the summer minimum to the cold season maximum. If the summer minimum extent is in a general, pronounced, downward direction, but spring max ice extent is holding steady or decreasing much less slowly it seems maybe the plot could reflect reality. But of course he's misusing that reality to imply something that is not true: i.e there's no "problem", by only highlighting a fraction of the story and then counting on his readers lack of curiosity and predjudices to make the incorrect assumption that arctic is is just fine - instead of for example seeing that the graph would represent the replacement of multiyear-age ice with one year old ice, among other things. "Skeptics", sheesh.
The most recent PIOMAS current ice volume anomaly graphic (31 January 2013) suggests to me that the Arctic Ocean is beginning to behave much more like a seasonally frozen lake or pond than a permanently frozen large expanse of ocean that melts around the edges. Note in particular the annual pattern in the graphed data from the 2010 maximum to the end of January, 2013:
http://psc.apl.washington.edu/wordpress/wp-content/uploads/schweiger/ice_volume/BPIOMASIceVolumeAnomalyCurrentV2.png?%3C?php%20echo%20time%28%29%20?
Yes, quite striking. Far be it from my place to criticize (because I'm way too ignorant) but the pattern of the last handful of years makes me wonder if we're overestimating the volume of ice left in the Arctic ocean. Those excursions just leap out at the eye.
doug,
I'm no expert either, but I trust that the recent volume calculations are fine. But I do wonder if the visible bouncing might be due to the shift to satellite observations which might possibly be better at recording the last stages of the summer melt season. That said, I think the explanation for the plunges is that there is now too little year-round ice both in terms of volume and area to keep the Arctic basin functioning as a year-round freezer. In other words, when most of the Arctic Ocean remained ice-covered throughout the melt season, the summer lows in ice area were reached by a fairly steady and slow process of melt around the edges and from below and this helped keep the volume loss low because the ice lid was still mostly in place. The last few melt cycles seem to simply reveal that the thin ice that does manage to form each winter is almost completely melting away with relative ease each summer--and then some of the old ice is also lost, hence the overall decline.
We need to remember that in previous years a fairly signficant portion of each winter's new ice survived to live another year, but that is no longer happening. I'd say that the magnitude of the annual range in volume is going to become even more dramatic--with much lower lows and gradually lower highs going forward until the summer ice volume bottoms out, whereupon the seasonally frozen pond/lake comparison will be very clear.
I'm curious about the relative temperatures of the ice in the pre-1980 days and more recently. I suspect that the current season's ice of the new Arctic is on average warmer, thanks to the influence of the ocean water beneath it and the relatively warmer air above it, at the start of the melt season than the old season's ice cover, which included more multiyear ice and had a colder atmosphere above it and potentially colder water below it, would have been.
It will be intersting to see if the climate models can explain thr 60% growth in artic ice this summer:
Link
[DB] Debunked here.
I doubt if climate models can explain the 2013 regression toward the mean, dadown. Why? Because big CMIP5 regime climate models aren't really designed for short-term projections. Modeling hasn't done well with Arctic sea ice in general. Note that we're a good 60 years ahead of the CMIP3 ensemble model mean for extent. In other words, Arctic sea ice could stabilize for half a century and the ice would still be ahead of its projected loss.
I'm curious, though: what does the 2013 melt season mean to you? I mean, what conclusions do you draw from it?
What I would like to know is why the ESA is not publishing a constantly updated graph of ice volume from cryosat as NSIDC does on ice extent. The weather patterns we have had in the summer of 2013 have a tendency to spread ice out (coriolis) and anything over 15% ice cover is recorded by NSIDC as full coverage. The increase in ice extent may be an reading glitch, at least to some extent. The ice volume results should clear up by how much the ice has actually increased between the middle of Sept 2012 and 2013 but the ESA seems oddly reluctant to tell us what their results are.
William, ice volume is not measured directly but calculated via the PIOMAS model. This is done monthly. You can get details here
...and US government shutdown is making data they need unavailable delaying the run.
Just wondering how the dismissives will fit this news into their "60% recovery" meme. Nah, they won't, they'll just quit talking about it.
Arctic Sea Ice Sits at Record Low for Mid-February - Climate Central