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Increasing southern sea ice: a basic rebuttal

Posted on 20 October 2010 by James Wight

Sea ice around Antarctica has been increasing over the last few decades that satellites have been measuring sea ice extent. Consequently, you often hear the refrain "Antarctica is gaining ice". First of all, it’s worth remembering that sea ice is not to be confused with land ice. This distinction might seem obvious, but the two are often confused in media reports. Sea ice is frozen seawater floating on the surface, whereas land ice is a layer of snow that has accumulated over time on a landmass. Antarctica is losing land ice at an accelerating rate.

However, it is clear that the extent of sea ice around the coast of the continent is growing. Why? The first explanation which comes to mind is that the Southern Ocean must be cooling. But on the contrary, the Southern Ocean has warmed by around 0.5°C in the three decades since satellites began measuring sea ice trends.

The true reasons for the increasing ice are a complex set of factors. One factor is an increase in precipitation over the Southern Ocean, which means more snowfall. However, this trend is expected to reverse in coming decades as the Antarctic continues to warm.

Finally, southern sea ice is not particularly important to the climate. Unlike land ice, sea ice doesn’t affect sea levels because it’s already displacing water. And unlike the situation in the Arctic, where disappearing sea ice is making the Arctic Ocean less reflective and amplifying Arctic warming, a decline in southern sea ice would not warm the Antarctic climate. For as long as climatologists have studied it, the Southern Ocean has been almost ice-free in summer, the time of year when it would receive enough heat from the Sun to have a large effect. The issue of southern sea ice is really just a distraction which diverts our attention from the more important issue of sea ice melt in the Arctic.

In conclusion, the increase of southern sea ice does not contradict global warming. The Southern Ocean is in fact warming, the increase of sea ice is due to a variety of factors, and sea ice is not as important to the Antarctic climate as it is to the Arctic.

This post is the Basic Version (written by James Wight) of the skeptic argument "Southern sea ice is increasing". If you'd like to study this topic in more detail, you can check out our Intermediate Version.

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Comments 1 to 21:

  1. Is the volume of Antarctic sea ice increasing, or just the extent. With the break off of a number of large pieces og sea ice in recent years, it seems to me that, like the Arctic, the thickness of Antarctic sea ice is probably diminishing.
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  2. If land ice was melting, I would expect it to cool the water into which it melts thus making it 'easier' for sea ice to form when the temmp drops in winter. Well that's my explanation for the increasing sea ice!
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  3. John, salinity and stratification are more likely to have major roles.
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  4. Ldavids - volume isn't an issue for sea ice in the Antarctic. There's little to no multi-year ice because it pretty well melts out fully each summer. Volume is only possible in the Arctic because sea ice doesn't melt out every year. Even the record minimum extent in 2007 was caused as much by winds piling the ice up towards the end of the season as it was by melting throughout the season. Unfortunately as extent and volume are steadily decreasing, more ice is melting out by the combination of warm waters from the Pacific and Atlantic and more water movement because of larger areas of open ocean within the Arctic basin.
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  5. John, remember the pure water melted from the land ice has a freezing point of 0C, (and of precipitation in the form of rain and snow). The freezing point of sea water varies but it's usually around -1.8C. Philippe's remark about salinity and stratification is the key.
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  6. Ldavids = Larsen B ice shelf pieces did become 'sea ice' after they broke off. Before that, as a floating ice shelf they were still attached and considered land ice. Yours is the first mention I've heard of the interesting idea of possible changes in the thickness of Antarctic sea ice. There aren't any multi-year issues, as in the Arctic. But have there been any changes in Antarctic sea ice thickness from year to year? Sigmond and Fyfe(2010) have apparently taken away the simpler to express, "its the ozone hole" explanation for the recent increases in Antarctic sea ice. So now we really will have to learn the much more complicated density/salinity/stratification/warmer-Southern=Ocean story.
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  7. This might belong under the intermediate version, but thinking of the complexity... It's pretty clear that less ice in the winter, (as mentioned in the article), when it's dark, would have negligible warming effect because albedo doesn't play a factor when it's dark. However, to add to what GT just wrote, if there is more ice at the beginning of the melt season, I'm thinking that will be a negative feedback to regional warming. I'm not saying it will be stronger than the other effects; I'm just thinking it will exist and wondering how it will all add up.
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  8. I know this is mainly about sea ice but the throw away line about land ice has to be countered. Wingham et al in 2006 found the land ice mass balance increasing 1992-2003. In fairness my own position would be that antarctic data is so short term, sparse and difficult to interpret that it seems foolhardy to make any sort of definitive comment about antarctic land ice trends. This 2007 Science review by the same authors is well worth a read if you want to get some perspective.
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  9. #8 HumanityRules, for starters, refer to Is Antarctica losing or gaining ice? at another page on this site. And then remember that the Wingham et al paper figures are for ice in the interior 72% of the ice sheet and not at the coastline, which is where by far most of the mass loss occurs (from the second page of the paper: "we extend an earlier survey (Wingham et al. 1998) in space to within, on average, 26 km of the ice sheet margin"). So the "throw away line" is correct, and your position reflects where things stood some years ago, not today.
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  10. HR #8: The same Duncan Wingham you MIS-cite here has been at the forefront of some of the subsequent studies (e.g. Pine Island Glacier) which have shown the coastal mass loss that Jeff talks about. As the lead scientist on the Cryosat-II mission he will also likely play an important part in figuring out what is going on with the Antarctic sea ice... as well as finally nailing down the volume losses for the Arctic sea ice, Greenland, and Antarctica.
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  11. Redirecting HR to another page when the article makes specific reference to land ice seems a touch pedantic. However, I don't dispute the GRACE data underpinning these assertions other than to note that ice loss may be proceeding at a steady pace rather than accelerating as per Velicogna (see here). However, ice loss is ice loss unless we come up with evidence of a major flaw in the GRACE methodology. At the same time, satellite data suggests that Antarctic waters are cooling, not warming. Trenberth's missing heat notwithstanding, I find this counterintuitive. Perhaps the hole in the ozone layer is still doing its work - Sigmond and Fyfe (2010) comprises a model rather than the last word on the subject.
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  12. chriscanaris, this image says it is for 10/18/2010. Do you have SST temperature anomaly data for a longer period of time (like 30 years or so)? That would be necessary in order to assert that Antarctic waters are cooling.
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  13. See the intermediate version of this article. The Zhang paper looks at SST 1979 to 2004 showing significant warming all around antarctica.
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  14. Philippe @ 12 Figure 7 in Verdy, Marshall, & Czaja suggests overall cooling since the 1980s. However, ice loss is ice loss until proven otherwise.
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  15. chriscanaris, The figure you just cited does not plot SST temperatures directly, please read more carefully. It is plotting the variability of SST's, which is a measure of how "spread out" the data is. A plot of variability is not going to tell you whether the data was going up or down, just that it was changing. Ironically, that paper is using the same raw SST data series (NCEP–NCAR reanalysis data) as the Zhang paper that scaddenp referred you to. If you are interested in actual SST trends in the antarctic, take a look at that paper. It is linked in the intermediate version of this post (or just look at the figures duplicated from that paper in the intermediate post).
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  16. E @ 15: I'm happy to stand corrected. However, I'd be interested if you have any data for 2004 -> roughly now.
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  17. chris, Not sure about anything later but the figure here runs up to 2007.
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  18. Much appreciated :-)
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  19. FIRST of all, according to the latest study Antarcticas land ice loss was cut in HALF. Secondly, its ONLY a measurement since 8 years. It requires serious cheerry picking and hasty conclusions to say anything about accelerating there. Thirdly, UAH and RSS show antarctica cooling since 30 years. Thermometers cover only a fraction. Fourthly, the SST has been decreasing since 1980. This was also Cooks misconception. I dont know where his claim was coming from (maybe Currys latest study???), but the data clearly shows cooling.
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  20. In order for Antarctic sea-ice to increase, then the temperature has to be lower than the freezing-point of land-ice; since 1) sea-ice is salt-water, and thus has a lower freezing-temperature; 2) land-ice has a higher altitude, and so the air is colder, and 3) it's further from the equator, and therefore gets less sunlight, and finally 4) it doesn't get warmed by ocean-currents. Therefore if antarctic land-ice is melting while sea-ice is increasing, then it MUST be due to geothermal-factors-- NOT ATMOSPHERIC. This fits with the general refutation of man-made global warming, as with the melting of Greenland-ice due to underground lava-flows. It also fits with the fact that there's a volcanic activity at the South Pole, and this conducts more geothermal heat than any other kind. Conclusion: CASE CLOSED.
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    Moderator Response: Please do not use all caps. It is considered yelling, and is prohibited by the Comments Policy.
  21. Teh all-caps are part of the Poe's Law costume. "Case closed." Nice!
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