<p>In my survey of sea ice extent for the same period (1979-2015) I found that the apparent positive trend in dispersed sea ice in the Antarctic in September is anomalous and possibly spurious for two reasons: (1) there was no trend in concentrated sea ice extent or in the degree of sea ice dispersion, and (2) the residuals of the OLS trend line showed patterns that might violate OLS assumptions. Please see 
<a href="http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2598152" rel="nofollow">http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2598152</a></p>

CC BY-SA 3.0
2015-04-25T10:46:41.903Z
2015-04-25T10:46:41.903Z
Jamal Munshi
<p>Every time I read a news article about Antarctic ice extent, I don't seem to have a clear answer as to what the deal is. If I look at the February sea ice extent from the National Snow and Ice Data Center (NSIDC), I get no trend that I can see:
<img src="https://i.sstatic.net/YKzXj.gif" alt="February extent">.</p>

<p>If I look at the September data from NSIDC, then I get a clear increase.<img src="https://i.sstatic.net/My43z.png" alt="September extent">. NSIDC even tells you what the trend is. </p>

<blockquote>
  <p>﻿Monthly Antarctic September ice extent for 1979 to 2014 shows an increase of 1.3% per decade relative to the 1981 to 2010 average.</p>
</blockquote>

<p>Finally, if I look at the monthly values it is even trickier: <img src="https://i.sstatic.net/HYDuc.png" alt="monthly extent"></p>

<p>What I can tell is that the minimum extent seems to be unchanged, while there is an increase in the maximum extent. If I where to analyze the trend using all the data, I wonder if any significant trend would be extracted.</p>

<p>I don't want to create any controversies, as I realize that the gains in the Antarctic (small increase of ~100,000 km2 per decade) are much smaller than the loss in the Arctic (decrease of ~500,000 km2 per decade) (<a href="http://nsidc.org/cryosphere/seaice/characteristics/difference.html" rel="noreferrer">NSIDC</a>).</p>

<p>My questions are: Considering the level of variability in coverage, can the Antarctic sea ice extent be considered at "record levels"? If so, what is the consensus on the causes of  this increase?</p>

CC BY-SA 3.0
2015-01-17T05:18:50.693Z
Very important: The increase in the Antarctic is in sea ice. When you look at the Antarctic as a whole, the trend is very sharply downward. The slight increase in sea ice in Antarctic winter is just that, a slight increase. The loss of ice over the continent of Antarctica more than offsets this slight increase.
David Hammen
CC BY-SA 3.0
2015-01-17T05:23:39.063Z
Do you want to add this aspect to the question? I could try as well
arkaia
CC BY-SA 3.0
2015-01-17T09:28:26.903Z
I do not know if this is true or not but if the ice is thinner it would be more spread out for the same volume
Catprog
<glaciology><antarctic><sea-ice>
Is Antarctic sea ice at record levels?
arkaia
# Is Antarctic sea ice at record levels?

(Asked by: username_0 on 2015-01-16)

Every time I read a news article about Antarctic ice extent, I don't seem to have a clear answer as to what the deal is. If I look at the February sea ice extent from the National Snow and Ice Data Center (NSIDC), I get no trend that I can see:
![February extent](https://i.sstatic.net/YKzXj.gif).

If I look at the September data from NSIDC, then I get a clear increase.![September extent](https://i.sstatic.net/My43z.png). NSIDC even tells you what the trend is.

> ﻿Monthly Antarctic September ice extent for 1979 to 2014 shows an increase of 1.3% per decade relative to the 1981 to 2010 average.

Finally, if I look at the monthly values it is even trickier: ![monthly extent](https://i.sstatic.net/HYDuc.png)

What I can tell is that the minimum extent seems to be unchanged, while there is an increase in the maximum extent. If I where to analyze the trend using all the data, I wonder if any significant trend would be extracted.

I don't want to create any controversies, as I realize that the gains in the Antarctic (small increase of ~100,000 km2 per decade) are much smaller than the loss in the Arctic (decrease of ~500,000 km2 per decade) ([NSIDC](http://nsidc.org/cryosphere/seaice/characteristics/difference.html)).

My questions are: Considering the level of variability in coverage, can the Antarctic sea ice extent be considered at "record levels"? If so, what is the consensus on the causes of this increase?

**Tags:** glaciology, antarctic, sea-ice

> **Comments:**
> **username_1**: Very important: The increase in the Antarctic is in sea ice. When you look at the Antarctic as a whole, the trend is very sharply downward. The slight increase in sea ice in Antarctic winter is just that, a slight increase. The loss of ice over the continent of Antarctica more than offsets this slight increase.  
> **username_0**: Do you want to add this aspect to the question? I could try as well  
> **username_2**: I do not know if this is true or not but if the ice is thinner it would be more spread out for the same volume  

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## 1 answers

### Answer by username_3 on 2015-04-25. Score: 2

In my survey of sea ice extent for the same period (1979-2015) I found that the apparent positive trend in dispersed sea ice in the Antarctic in September is anomalous and possibly spurious for two reasons: (1) there was no trend in concentrated sea ice extent or in the degree of sea ice dispersion, and (2) the residuals of the OLS trend line showed patterns that might violate OLS assumptions. Please see
<http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2598152>


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