From Watts Up With That?

News Brief by Kip Hansen

A new study out of the University of Florida and the Colorado School of Mines  written by Emma J. MacKie, Joanna Millstein, and Katherine A. Serafin and titled:

“47 Years of Large Antarctic Calving Events: Insights From Extreme Value Theory”

states that (from the Abstract):

“We use 47 years of iceberg size from satellite observations. Our analysis reveals no upward trend in the surface area of the largest annual iceberg over this time frame. This finding suggests that extreme calving events such as the recent 2017 Larsen C iceberg, A68, are statistically unexceptional and that extreme calving events are not necessarily a consequence of climate change.”

The Conclusion is a little more precise:

“…our analysis shows that maximum calving size has not increased over our study interval. Rather, extremely large calving events are likely typical of a healthy ice sheet system wherein exists a quasi‐stable cycle of calving front advance and retreat. The lack of an upward trend in annual maximum iceberg area could be attributed to an overall increase in the number of smaller calving events, which may inhibit the development of extremely large calving events.”

As with all results of these types of studies, one must read carefully what the authors are saying. 

1. Over the last 47 years (the extent of reliable data), “maximum calving size has not increased”.

2.  “extremely large calving events are likely typical of a healthy ice sheet system wherein exists a quasi‐stable cycle of calving front advance and retreat.”

3.  There has been a “…lack of an upward trend in annual maximum iceberg area” .

4.   Then follows a couplet of face-saving  “could be” and “might”: “could be attributed to an overall increase in the number of smaller calving events, which may inhibit the development of extremely large calving events.”

Basically, the villain Climate Change has been shown not to be causing an increase in massive icebergs to calve off the ice shelves of Antarctica.

Rather, it seems, from their study, that large icebergs breaking off is part of the perfectly normal and expected behavior of these ice shelves. 

This is a serious study based on a great deal of computational power and some novel approaches to “to understand their [sea ice and massive icebergs] physical drivers, temporal trends, and future likelihood” including extreme value theory (EVT).

The authors attempt to mitigate the unexpected findings by postulating that instead of more massive icebergs, there may have been many smaller icebergs:  “While extreme calving events have not grown in area over the observational period, overall ice shelf area is decreasing (Greene et al., 2022). Our results suggest that this mass reduction is primarily driven by small calving events.”

Let’s just check that “overall ice shelf area is decreasing” (which should mean over the 47-year study period): (These two graphs cover approximately the same years as the study, 1979-2024/5, whereas the study uses 1976-2023).

he above is Antarctic Sea Ice Extent, in millions of square kilometers, at the height of the Antarctic Summer, with 2025 coming in in the middle of the pack and in the same general range as the earliest years, the 1980s.

This graph is Sea Ice Volume….and shows that 2024 was exceptionally low, but, if we highlight the higher years since 2010, we get this:

Most of the years in the last 15 years have been the higher/highest  volume years.    So maybe, the authors could have taken a closer and a broader look at the longer-term statistics.  The authors cite a single study, Greene et al. (2022), in support of  “overall ice shelf area is decreasing”.

Bottom Lines:

1.  The repeated claim that Antarctica is producing more and more and larger and large icebergs is not correct.  There is no trend (and possibly a negative trend) in massive icebergs calving from Antarctic ice shelves. 

2.  The large icebergs calved in recent years have not been caused by Climate Change, but are apparently just part of the long-term cycle of ice shelf growth and decline.

3.   Concerns over Antarctic Ice Shelf area (km²) seem overheated…the area covered by ice shelves off the coasts of Antarctica is highly variable and currently in line with the extent seen in the 1980s. 

4.  Media claims to the contrary are false and based primarily on untrue Climate Crisis narrative talking point:  “The icecaps are melting”. 

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Author’s Comment:

Arctic Sea Ice, what passes for the Northern polar ice cap, is currently in a low ice mode, similar to that seen in the 1930s.  So much so that commercial shipping again is possible over the Northeast Passage (Northern Sea Route) from Europe to Asia for a short season every year.  Russia is using that window in the seasonal ice to ship its LNG from its Arctic LNG 2 project  to China and elsewhere.

Antarctic Sea Ice is highly variable in both extent and ‘thickness’.  Extent has been ‘measured’ by satellite using images which can be compared year to year.  Thickness is currently estimated using gravity measurements from satellites and by the “Global Ice-Ocean Modeling and Assimilation System (GIOMAS).”

As we all know, melting sea ice does not add to sea level or cause sea level rise.  Only melting land ice (glacial ice) can do so.

Less ice at the northern pole of the planet is a good thing as it allows shorter shipping routes in our ever more interdependent commercial societies.    Sea ice in Antarctica is a negligible issue.  Land ice mass on Antarctica is a scientific controversy.

Thanks for reading.

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