Antarctic icebergs still exist today where 1700-era sailors spotted and tracked them

Antarctic sea ice [image credit: BBC]

Probably not the result that was expected from this study. Captain Cook’s descriptions of iceberg sightings still seem valid. Is saying ‘large icebergs…are not as sensitive to climate change’ enough to avoid raising questions about modern global warming theories?
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A new study comparing observations of large Antarctic icebergs from the 1700s with modern satellite datasets shows the massive icebergs are found in the same areas where they were pinpointed three centuries ago, reports Phys.org.

The study shows that despite their rudimentary tools, the old explorers truly knew their craft, and it confirms that the icebergs have behaved consistently for more than 300 years.

Using primarily the journal records of Captain James Cook’s 1772–1775 Antarctic circumnavigation on the HMS Resolution (where he noted the positions of hundreds of icebergs), a trio of researchers from Brigham Young University, NASA’s Jet Propulsion Laboratory and the University of Washington’s School of Oceanography made comparisons with the two largest modern datasets available today: the BYU/National Ice Center and Alfred Wegener Institute datasets.

They found that Cook’s description of the iceberg plume east of Antarctica’s Amery Ice Shelf, along with iceberg distributions in the Weddell, Ross and Amundsen Seas, agree with modern data.

They also found additional iceberg tracking by Edmond Halley in 1700, Lozier Bouvet in 1739 and Edward Riou in 1789 are consistent with modern observations.

“Where they saw icebergs, we see icebergs now; where they didn’t seem them, we don’t see them,” said study coauthor David G. Long, BYU professor of electrical and computer engineering. “The old data from these explorers may not have been very good, but it’s all that we’ve got from that time—and it’s good enough.”

Cook’s observations make up 95% of the historical data used for comparison in the study. His crew used the Larcum Kendall K1 watch in combination with a sextant to track longitude on their journey. The K1 watch carried a heavy price tag (£450—the ship Cook sailed for the trip, the HMS Resolution, cost £1,800) so Cook took great care of the device, requiring the commander, first lieutenant and astronomer all present when it was used.

Lead study author Seelye Martin extracted Cook’s iceberg observations from a line-by-line search of Cook’s journal-turned-book about his journey: “A Voyage Towards the South Pole, and Round the World.” It turns out that when possible, Cook recorded his position alongside his iceberg observations, which he referred to as “ice islands,” “ice isles,” and “hills of ice.”

“Cook kept pretty good records, but they’re not perfect,” Long said. “They’re basically journal entries. He took some days off. Sometimes he would just say ‘saw a lot of ice in the ocean.’ Wish it was a little better, but on the other hand it was pretty unique.”

Fortunately, Cook’s onboard astronomer, William Wales, also recorded iceberg observations, which helped fill in a few gaps in Cook’s records.

Full report here.
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Study: Comparison of Antarctic iceberg observations by Cook in 1772–75, Halley in 1700, Bouvet in 1739 and Riou in 1789 with modern data
Published online by Cambridge University Press: 12 December 2022