Tag Archives: Professor Julian Dowdeswell

THE WEDDELL SEA AGAIN

2 Jan

Happy New Year!!

This January, Professor Julian Dowdeswell of the Scott Polar Research Institute will lead an international research team in the long planned expedition to the Weddell Sea. This expedition aims to investigate ice shelves around the Weddell Sea, particularly the Larsen C Ice Shelf. It also hopes to locate the wreck of Shackleton’s ship Endurance, which sank in the area in 1915.

The expedition’s progress and achievements will be followed internationally – in addition the Royal Geographical Society has created an educational programme aimed at engaging the interest of children from primary level upwards.

The Weddell Sea was discovered in 1823 by James Weddell, the British sea captain/ sealer, who sailed as far south as 74°15´S. It is a vitally important ecosystem – penguins, seals, whales, krill, corals and sponges thrive there. It is shaped as a huge bay; Coats Land (discovered by William Speirs Bruce in 1904) is at one extremity, the Antarctic Peninsula is on the other. It has been described as ‘the most treacherous and dismal region on earth’.[i]

An important aim will be to investigate the shapes of the ice shelf bases. Ice shelves stop ice from flowing outwards from the continent. Thinning of the ice shelves results in increased flow from the interior, which, in turn, causes a rising global sea level. The sea floor will be examined to assess the stability of the ice shelf.

Although the general circulation of oceans is determined by wind driven currents, the Weddell is one of few locations where deep and bottom water masses contribute to global thermohaline circulation. Bottom water is the lowest water mass with distinct characteristics in terms of physics, chemistry, and ecology and a temperature of -0.7 °C or colder. The thermohaline circulation is the motor of deep ocean currents and is driven by density gradients influenced by surface heat and freshwater fluxes. The description relates to thermo- temperature-and –haline, salt content.

The Larsen Ice Shelf, in the northwest part of the Weddell Sea, is named after Captain Carl Anton Larsen, master of a Norwegian whaling vessel who sailed along the ice front as far as 68°10′ S. in 1893. From north to south segments of the shelf are called Larsen A, B, and C (the largest), and Larsen D, E, F and G.

The 2019 expedition is focused on the Larsen C ice shelf from which a giant ice berg calved off in July 2017 (twice the area of Luxembourg), reducing the size of the iceshelf by approximately12%.

 

 

 

Dowdeswell and Shears[ii] explain in the ‘Geographical’ that measurements will be taken of salinity and temperature of the sea adjacent to the shelves, samples of marine life will be obtained and the sea ice thickness will be measured by aerial drones. Autonomous Underwater Vehicles will make echo soundings of the underwater shape of the ice shelf base, the roughness of which is a vital parameter in numerical modelling of future ice shelf stability. Ernest Shackleton’s Ship will be searched for.

Whether the team will be able to achieve these aims is uncertain — the conditions are so unpredictable that attempts to navigate south could be unsuccessful, but this expedition is of pivotal importance in attempting to obtain long-term prognostic information relating to global warming. I hope this important analysis of the Weddell Sea will be successfully accomplished.

[i] Henry, T.R.,1950,The White Continent

[ii] Dowdeswell, J. Shears, J. 2019, Geographical, p.10

 

 

 

 

Finding Shackleton’s Endurance

5 Jun

FINDING SHACKLETONS ‘ENDURANCE’

 

Recently a Victorian merchant vessel, the ‘West Ridge’, lost off the west coast of Australia over 100 years ago, was located during the search for the still tragically missing MH370, which disappeared whilst flying from Malaysia to China, in March 2014.

‘West Ridge’ ship wreck found 12000ft beneath Southern Indian Ocean December 2015

Area of Southern Indian Ocean where West Ridge, a barque lost in July 1883

credit:Australian Transport  Safety bureau /ATP/Getty

 

 

Now it is hoped that the final location of another lost ship, Shackleton’s Endurance, will be found on the seabed of the Weddell Sea as a part of an expedition that has, primarily, important scientific aims.

As is well known, Shackleton’s ship became trapped in the icy grip of the Weddell Sea in February I915. She drifted slowly and helplessly in a clockwise direction around the Weddell until October 1915, when the pressure of the sea ice started to crush the stern, and the sea finally poured in. The crew had to abandon ship to begin their precarious existence on ice flows.

Endurance sank on November 1915 – ‘She’s going boys’

 

October 1915 Endurance being crushed in the Weddel Sea – Sank in November 1915

credit : Frank Hurley

The proposed expedition aims to increase scientific information about the continent.

Glaciologists, geologists, geophysicists, marine biologists and oceanographers make up the team, which comes from, I understand, the Scott Polar Research Institute (SPRI), the Nekton Foundation, the University of Oxford, the University of Canterbury (New Zealand) and the University of Cape Town. The scientists will examine marine life in the Weddell Sea, and study the exposed cavities that lie beneath the Larsen C. ice shelf, one of the largest ice shelves in Antarctica, following the breakaway, in July 2017, of Iceberg A-68.

Professor Julian Dowdeswell, Director of SPRI, says that the study is relevant to all the ‘fringes’ of Antarctica and the ice shelves around it. Ice shelves are part of what secures the ice flow from the interior, if they break off, the interior ice flows faster. This is of general concern, because interior ice flows contribute to global sea level rise.

The Weddell Sea expedition will start in January 2019, (when sea ice is at its thinnest). Agulhas11 an icebreaking polar supply and research vessel will sail into the western part of the Weddell Sea, which has actually only been visited rarely since Endurance sank there in 1915.

The work will focus on the area in and around Iceberg A-68; the iceberg that broke off. It is massive, it has a surface area of 2,240 square miles (5,800 square kilometers), about four times the size of London!

Also cavities under the shelf of Larsen C itself will be explored, the seafloor mapped, and the overhanging ice canopy investigated. Samples of ice will be extracted from the shelf. These can be read (like tree rings) to see the ebb and flow of the ice over time. Because A-68 split off, there is concern as to whether Larsen C may be prone to collapse and the expedition aims to establish the past history of ice advance and retreat, to see if old grounding lines – the locations where Larsen’s feeding glaciers previously rested on the seafloor, have moved backwards and forwards on a fairly regular basis, or only retreated. In this way it is hoped to put the recent changes at the peninsula into longer-term context.

The Captain of Endurance, New Zealander Frank Worsley, was a navigator of enormous experience. He subsequently navigated the James Caird, a twenty-five foot boat, through the turbulent waves of Drake’s Passage and the South Atlantic, for 800 miles from Elephant Island to South Georgia. Only three sightings of the sun could be made on this sail. When Endurance sank in 1915, Worsley recorded her position as 68˚39′ 30.0″S. 52° 26′ 30.0″W, but locating the ship poses considerable challenges – she is 10,000 feet below the sea surface, the ice conditions on the surface can vary greatly from year to year, also the state of the ship will be poor, though it is thought that the hull will be reasonably intact.

If Endurance is found she will be surveyed, photographed and filmed. Undersea drones will document any marine life. The expedition obviously aims to record Endurance’s exact location, so the wreck can be listed as a historic monument under the Antarctic Treaty. Nothing will be removed from the site if the ship is found.

This is an important expedition with important implications. Finding Endurance would be a bonus, though it is interesting to consider whether Shackleton would have preferred to let her remain undisturbed.

 

Tags ‘West Ridge’, ‘Endurance’, Professor Julian Dowdeswell,  Frank Worsley, ‘James Caird’, Larsen C, Iceberg A-68, ‘Agulhas II’, South Georgia.

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