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Robert Falcon Scott's ill-fated expedition party at the South Party, 17 January 1912
Robert Falcon Scott's ill-fated expedition party at the South Pole, 17 January 1912.
24 November 2016 7:25

Captain Scott’s expedition logs reveal Antarctic sea ice history

Robert McSweeney

Robert McSweeney

Robert McSweeney

Robert McSweeney

24.11.2016 | 7:25am
Sea iceCaptain Scott’s expedition logs reveal Antarctic sea ice history

On the 14 December 1911, explorer Roald Amundsen and his team planted the Norwegian flag on the snow-covered South Pole. They had beaten the British team, led by Captain Robert Scott, by 33 days.

This was the Heroic Age of Antarctic Exploration, where explorers ventured into unknown parts of Antarctica, and many – including Scott – lost their lives in the process.

A hundred years later, a new study describes how the records kept during these expeditions provide insights into how sea ice around Antarctica has fared over time.

The findings suggest that while the response of Antarctic summer sea ice to human-caused climate change may be less dramatic than in the Arctic, sea ice cover may have declined by as much as 14% over the last 100 years.

Data gaps

If we take just the satellite record, which began in 1979, Antarctica’s sea ice has shown a small but steady increase. Over in the northern hemisphere, meanwhile, Arctic sea ice has declined rapidly over the same period.

The reasons for the contrasting fortunes of sea ice at the Earth’s poles has prompted a lot of speculation in the media and by scientists. A recent study, for example, pinpointed a natural shift in the Pacific Ocean as a key factor in a growth spurt of Antarctic sea ice between 2000 and 2014.

One of the limitations to understanding exactly how and why Antarctic sea ice is changing is the relatively short length of satellite data records, says Dr Jonathan Day, co-author of the new study published in The Cryosphere. He explains to Carbon Brief:

“Relatively little is known about the state of Antarctic sea ice before continuous satellite records began in the 1970s, making it hard to understand if [the increase] is a trend.”

Day’s study helps to fill in this data gap using ship logbooks kept by Antarctic explorers during the Heroic Age of Antarctic Exploration between 1897 and 1917. As part of these missions, scientists recorded the position and state of the sea ice in ships’ logbooks, explains Day:

“These records were very diligently kept by trained meteorologists onboard ship, so the quality of the record keeping is high.”

Photograph entitled: 'With Captain Scott [Royal Navy] to the South Pole (British Antarctic Expedition)'. Steam Yacht 'Terra Nova' with dogs and men standing on ice near by', by Herbert Ponting (1870-1935)

Photograph entitled: ‘With Captain Scott [Royal Navy] to the South Pole (British Antarctic Expedition)’. Steam Yacht ‘Terra Nova’ with dogs and men standing on ice near by’, by Herbert Ponting (1870-1935). c1911.

Some expeditions were primarily concerned with land exploration or the race to the South Pole and so only took a few records of sea ice. Others missions mapped undocumented coastlines, and hence gathered more data as ships regularly passed in and out of areas of sea ice.

‘Surprisingly comparable’

The researchers digitised the logbooks from 11 expeditions and added the data by hand into spreadsheets. They were helped by various other research groups as part of the International Comprehensive Ocean-Atmosphere Data Set (ICOADS), a worldwide effort to recover weather data from ships’ logbooks.

You can see the routes that the explorers took in the map below.

Map of expedition routes taken by ships used in the study. Source: Edinburgh & Day (2016)

Map of expedition routes taken by ships used in the study. Source: Edinburgh & Day (2016)

The sea ice records are predominantly for the southern hemisphere summer – from November to March – because that’s when the explorers tended to sail to the Antarctic, taking advantage of the seasonal lows in sea ice extent.

From these records, the researchers created a dataset of 191 sea ice edge positions, providing “an almost circumpolar picture of the Antarctic summer sea ice edge” for 1897-1917, the paper says.

Comparing the dataset with modern satellite records, the researchers find that Antarctic summer sea ice extent was “surprisingly comparable” to what it is today.

That said, the logbook records also suggest that Antarctic summer sea ice has declined by up to 14% between the Heroic Age and the present day.

And the results do show some dramatic changes, the researchers note, particularly in the Weddell Sea. The ice edge positions recorded by expeditions in the early 1900s reveal that sea ice extended much further north than any time in the last 25 years, says Day.

Preserving old records

While a 14% loss is not an insignificant amount, it’s smaller than some of the changes in Antarctic sea ice recorded during the middle of the 20th century, as estimated from whaling ship logbooks, the paper says.

The findings suggest that Antarctic sea ice has fluctuated substantially through the last century, rather than experiencing the sort of steady trend seen in the Arctic over many decades.

This indicates that summer sea ice in the Antarctic is heavily influenced by natural fluctuations in the climate system, which can mask the impact of human-caused climate change, says Day:

“What this study shows is that summer sea ice in the Antarctic might not be particularly sensitive to a warming climate compared to the Arctic, however it does leave open the possibility that there has been a decrease in ice extent of at most 14%.”

Day discusses his study in the video below.

The study highlights what’s happening to sea ice can be quite different in each of the Earth’s poles, says Florence Fetterer, principal investigator at the National Snow and Ice Data Centre (NSIDC), who wasn’t involved in the study, but peer-reviewed the paper. She tells Carbon Brief:

“The study reinforces the idea that looking at Arctic and Antarctic ice separately is the best way to understand decadal and long-term trends, because it suggests significant decadal and inter-decadal variability in southern hemisphere ice extent going back much further than the last 30 years.”

Fetterer – who recently wrote a guest article for Carbon Brief on piecing together a record of Arctic sea ice back to 1850 – also says the study highlights how important it is to find and preserve old observations:

“I hope it will bring attention to international projects like Old Weather that are working to ensure that the observations are not lost.”

Edinburgh, T. & Day, J. (2016) Estimating the extent of Antarctic summer sea ice during the Heroic Age of Exploration, The Cryosphere, doi:10.5194/tc-10-2721-2016.

Sharelines from this story
  • Captain Scott’s expedition logs reveal Antarctic sea ice history
  • Al Rodger

    I see you spotted the 1987 typo but the correction should be 1897 not 1887.

    Your reference to De la Mare (1997) to show the more extensie Antarctic ice (relative to today) of the mid-twentieth century reminds me of a long interchange I once had here at CarbonBrief with a commenter who was obviously Peter Lilley MP. The commenter’s denial mechanisms were well exposed by the end of the interchange with the commenter being tasked to find evidence of a melty 1930s Antrarctica. He failed to return. Perhaps he found De la Mare (1997) and gave up the fight to return to his happy delusions. If he had returned, I recall that I did have De la Mare (1997) waiting for him.

    • Robert McSweeney

      Hi Al – have corrected (again!), thanks.

    • Lionel Smith

      Shame that comment thread in which Lilley took part can no longer be
      found. I still recall his exchange with Dr Emily Shuckburgh at ‘The
      Energy and Climate Committee on the IPCC’s 5th Assessment Review on 11
      February 2014’.

      Thanks for that link.

      • Al Rodger

        Lionel Smith,
        It would have presumed my lengthy interchanges with my ‘Lilley’ started off in the comment thread below this <a href=""CarbonBrief story which was just over 4 years ago and it seems Disqus only keep comments for 4 years. The commenter appeared as Nullius in Verba & the last echoes of our lengthy interchanges can still be seen in this deniosphere blog which contains in a little tirade by Baab Tiiiizdaaaale who calls me one of those “people who don’t want to learn.” I think I must have rather upset poor old Baab by pointing out that his grand theory would require a humungous amount of energy coming out of the oceans to ramp up global temperatures and keep them ramped up until the next El Nino comes along to repeat the process (according to Baab). My comment that Baab is silent on the need to find 200Zj is apparently “misdirection and lies!!” but that silence continues unbroken………

        • Lionel Smith

          Thanks for your time and reply Al. Love Tiiizdaaale’s projection.

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  • john

    I notice they mention Antarctic sea ice
    As they should.
    However just remember Antarctica is a land based place.
    The arctic is water surrounded by land totally different.
    My thoughts are that when a land based ice area has wind swirling around it as against a water based area there would be a difference.

    As to how to explain the sudden downward trend both in the Arctic and Antarctica is rather confronting.

    As to say this is some how natural I would submit NO it is not.
    There is zero forcing from the sun to earth.
    So what is causing this?
    Hint perhaps the situation where those molecules in the air are actually reflecting the energy they get and reflecting it in all directions and some is down,side, up however the outcome is that earth is heating up.

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