Heroes of Antarctica clues show century of no sea ice change

The Heroes of Antarctica, such as Captain Robert Scott and Sir Ernest Shackleton, left clues that suggest that for the past century the area of sea ice around the Antarctic has hardly changed at all. A new study, led by scientists from the University of Reading in England, examined ice observations recorded in the ships’ logbooks of the Heroes of Antarctica.

Scientists know much more about what has happened to sea ice volumes near the North Pole compared to the South Pole region. Arctic sea ice has shrunk in volume considerably over the last hundred years. Most people assumed that Antarctica had suffered the same fate.

This latest study suggests that Antarctica has fared significantly better than the Arctic, at least so far.

Heroes of Antarctica mapMap of the expedition routes taken by the ships of the Heroes of Antarctica used in this study. (Image: the-crysphere.net)

The Heroes of Antarctica

The Heroes of Antarctica were famous explorers that went further than any human had ever gone during the Heroic Age of Antarctic Exploration at the end of the 19th and beginning of the 20th centuries.

Historians say the period ended in 1917, with the survivors of Shackleton’s Imperial Trans-Antarctic Expedition stepping ashore in Wellington, New Zealand.

The most famous Heroes of Antarctica were Adrien de Gerlache (Belgian), Carsten Borchgrevink (Anglo-Norwegian), Robert Falcon Scott (British), Erich von Drygalski (German), Otto Nordenskiöld (Swedish), William Speirs Bruce (British), Jean-Baptiste Charcot (French), Sir Ernest Shackleton (British), Nobu Shirase (Japanese), Roald Amundsen (Norwegian), Wilhelm Filchner (German), Douglas Mawson (Australian), and Aeneas Mackintosh (British).

Study leader Dr. Jonathan Day, from the Department of Meteorology at the University of Reading, and Tom Edinburgh, also from Reading, but who is currently at the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge, published details of their study and their findings in the journal Cryosphere.

They compared ships’ logs of the explorers during the Heroic Age of Antarctic Exploration to modern satellite data regarding the sea ice in Antarctica.

Comparing ship and satellite sea-ice observationsComparison of satellite-derived and ship-observed ice edge latitude, which indicates no change in position (one-to-one line). The dashed line gives an estimate of the southward offset you’d expect when comparing satellite vs. ship observations, as calculated by Worby and Comiso in 2004. (Image: the-cryosphere.net)

The authors say that their findings suggest that the Antarctic sea is considerably less sensitive than the Arctic to the effects of global warming. The Arctic registered a dramatic decline in sea ice volume during the 20th century.

This latest research estimates that Antarctic summer sea ice shrank by no more than 14% in the ‘low years’ since the early 1900s.

Dr. Day said:

“The missions of Scott and Shackleton are remembered in history as heroic failures, yet the data collected by these and other explorers could profoundly change the way we view the ebb and flow of Antarctic sea ice.”

“We know that sea ice in the Antarctic has increased slightly over the past 30 years, since satellite observations began. Scientists have been grappling to understand this trend in the context of global warming, but these new findings suggest it may not be anything new.”

“If ice levels were as low a century ago as estimated in this research, then a similar increase may have occurred between then and the middle of the century, when previous studies suggest ice levels were far higher.”

This is the first study to shed light on sea ice extent during the pre-1930s period. It suggests that the levels that existed during the Heroes of Antarctica expeditions were actually similar to today, at between 5.3 and 7.4 million square kilometers (2.04 and 2.8 million square miles).

Only one region – the Weddell Sea – had considerably large ice cover one hundred years ago. The Weddell Sea is a deep embayment of the Antarctic coastline that forms the southernmost tip of the Atlantic Ocean. It is part of the southern Ocean and contains the Weddell Gyre.

Sea ice rose in 1950s

According to published estimates, the extent of sea ice in Antarctica was considerably higher during the 1950s, after which there was a steep decline to approximately 6 million square kilometers (2.3 square miles) in recent decades.

The study suggests that Antarctica’s climate may have fluctuated considerably throughout most of the 20th century, swinging between decades of low ice cover to decades of high ice cover. There is no evidence of a gradually declining trend.

This study builds on efforts by researchers across the world to recover old climate and weather data from ships’ logbooks. If you wish to volunteer to recover more data, go to oldweather.org.

Regarding the Southern Ocean, Dr Day said:

“The Southern Ocean is largely a ‘black hole’ as far as historical climate change data is concerned, but future activities planned to recover data from naval and whaling ships will help us to understand past climate variations and what to expect in the future.”

Heroes of AntarcticaTwo Heroes of Antarctica. Left: Captain Robert Falcon Scott CBO RN (1869-1904). Right: Sir Ernest Henry Shackleton CBO OBE FRGS (1874-1922). At the end of the 19th and beginning of the 20th centuries, during the Heroic Age of Antarctic Exploration, explorers were followed, admired and talked about with excitement and wonder. It was not until 1969, when Neil Armstrong, Edwin Aldrin and Michael Collins became the first humans to walk on the moon, that the world had brave and wonderful heroes of exploration again.

Two Heroes of Antarctica

Captain Scott died along with his team mates in 1912. He missed being the first human to reach the South Pole by a matter of just a few weeks. Sir Ernest Shackleton’s ship sank after it got trapped in ice in 1915.

In an Abstract that precedes the main paper in the journal, the authors wrote:

“We have analysed observations of the summer sea ice edge from the ship logbooks of explorers such as Robert Falcon Scott, Ernest Shackleton and their contemporaries during the Heroic Age of Antarctic Exploration (1897–1917), and in this study we compare these to satellite observations from the period 1989–2014, offering insight into the ice conditions of this period, from direct observations, for the first time.”

“This comparison shows that the summer sea ice edge was between 1.0 and 1.7° further north in the Weddell Sea during this period but that ice conditions were surprisingly comparable to the present day in other sectors.”

Citation: Estimating the extent of Antarctic summer sea ice during the Heroic Age of Antarctic Exploration,” Tom Edinburgh and Jonathan J. Day. The Cryosphere 10, 2721-2730, 2016. DOI: 10.5194/tc-10-2721-2016. Published 21 November 2016.

Video – Sea ice volumes in Antarctica

In this video, Dr. Day explains the findings of the research.