A massive iceberg, with an area 6,000 sq km (2,300 sq miles), twice the size of the European country of Luxembourg, larger than the US state of Delaware and weighing one trillion tonnes, is about to enter the ocean.
The iceberg, called iceberg A68 by the US National Ice Centre, broke free from the Larsen C Ice Shelf in Antarctica in July 2017, and has moved so far north it is now at the limit of the continent’s perennial sea-ice. The iceberg has shed very little of its bulk over the past two and a half years.
A scientist says iceberg A68 will struggle to hold it together when it reaches the Southern Oceans rougher waters.
“With a thickness to length ratio akin to five sheets of A4, I am astonished that the ocean waves haven’t already made ice cubes out of A68,” Professor Adrian Luckman from Swansea University, UK, told BBC News.
“If it survives for long as one piece when it moves beyond the edge of the sea-ice, I will be very surprised.”
Prof Luckman has been observing the progress of iceberg A68 through images captured by the European Space Agency Sentinel-1 satellites.
— Adrian Luckman (@adrian_luckman) July 11, 2019
He said that the darkening of the images towards the end of the sequence shows how surface melt in the height of the Antarctic summer causes the ice surface to be much less reflective of microwave energy from the satellite.
A68 split from the Larsen C Ice Shelf hardly moved for years, with its keel believed to have been grounded on the seafloor.
Prevailing winds and currents eventually began to push it northwards along the eastern coast of the Antarctic Peninsula, and the push has sped up.
When the iceberg, currently at 63 degrees South latitude, passes the tip of the peninsula, it should be swept northwards towards the Atlantic – a path researchers know as “Iceberg Alley”.
Antarctica’s greatest icebergs can reach the British Overseas Territory of South Georgia at roughly 54 degrees South. The biggest ever recorded iceberg in the modern era was the 11,000-sq-km block called B15, which calved from the Ross Ice Shelf in 2000.
One of its last remnants, now measuring 200 sq km, is halfway to the South Sandwich Islands, east of South Georgia.
The only sighting of A68 was by MS Expedition, an expedition cruise ship owned and operated by the Canada-based G Adventures, on 9 December last year.