Massive Iceberg’s Split Exposes Hidden Ecosystem

Sep 28, 2017

By Jo Marchant

Biologists are racing to secure a visit to a newly revealed region of the Southern Ocean as soon as it is safe to sail there. One of the largest icebergs ever recorded broke free from the Larsen C ice shelf on the Antarctic Peninsula in July. As it moves away into the Weddell Sea, it will expose 5,800 square kilometres of sea floor that have been shielded by ice for up to 120,000 years. If researchers can get to the area quickly enough, they’ll have the chance to study the ecosystem beneath before the loss of the ice causes it to change.

“I cannot imagine a more dramatic shift in environmental conditions in any ecosystem on Earth,” says Julian Gutt, a marine ecologist at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany.

It is difficult for Antarctic scientists to respond quickly to sudden events, because polar-research vessels are usually booked  months, if not years, in advance. A German research mission led by Boris Dorschel, head of bathymetry at the Alfred Wegener Institute, was already scheduled to visit the Larsen area and will now include a biodiversity survey of the exposed region in March 2019. 

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6 comments on “Massive Iceberg’s Split Exposes Hidden Ecosystem

  • This type of environment was filmed for David Attenborought’s BBC Frozen Planet series!

    ‘Brinicle’ ice finger of death filmed in Antarctic

    A bizarre underwater “icicle of death” has been filmed by a BBC crew.

    With timelapse cameras, specialists recorded salt water being excluded from the sea ice and sinking.

    The temperature of this sinking brine, which was well below 0C, caused the water to freeze in an icy sheath around it.

    Where the so-called “brinicle” met the sea bed, a web of ice formed that froze everything it touched, including sea urchins and starfish.

    The unusual phenomenon was filmed for the first time by cameramen Hugh Miller and Doug Anderson for the BBC One series Frozen Planet.

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  • @OP – It is difficult for Antarctic scientists to respond quickly to sudden events,
    because polar-research vessels are usually booked months,
    if not years, in advance.
    A German research mission led by Boris Dorschel, head of bathymetry at the Alfred Wegener Institute,
    was already scheduled to visit the Larsen area
    and will now include a biodiversity survey of the exposed region in March 2019.

    UK scientists will lead an international expedition to the huge new iceberg that recently calved in the Antarctic.

    A-68, which covers an area of almost 6,000 sq km, broke away in August.

    Researchers are keen to investigate the seafloor uncovered by the trillion-tonne block of ice. Previous such ventures have discovered new species.

    The British Antarctic Survey has won funding to visit the berg and its calving zone in February next year.

    It will use the Royal Research Ship James Clark Ross.

    BAS cautions, however, that the final green-light will depend on the berg’s position at the time and the state of sea-ice in the area.

    A-68 will need to be well clear of the Larsen Ice Shelf from which it calved, and any marine floes on top of the water will have to be sufficiently thin to allow the JCR access.

    “It’s fantastic news to have won approval,” BAS marine biologist Dr Katrin Linse, who will lead the cruise, told BBC News.

    “Antarctic vessels are normally booked out years in advance and for our funders, Nerc, to give us the opportunity on this urgency grant to go this coming season is brilliant.”

    Copernicus Sentinel 1 Data/BASE – A large gap is opening between the berg and the Larsen Ice Shelf (image from 2 October) –See link for satellite image.

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  • High-resolution satellite systems, are giving more detailed insights into the melting of Antarctic glaciers and the breaking up of ice shelves!

    Satellites spy Antarctic ‘upside-down ice canyon’

    Scientists have identified a way in which the effects of Antarctic melting can be enhanced.

    Their new satellite observations of the Dotson Ice Shelf show its losses, far from being even, are actually focused on a long, narrow sector.

    In places, this has cut an inverted canyon through more than half the thickness of the shelf structure.

    If the melting continued unabated, it would break Dotson in 40-50 years, not the 200 years currently projected.

    “That is unlikely to happen because the ice will respond in some way to the imbalance,” said Noel Gourmelen, from the University of Edinburgh, UK.

    “It’s possible the area of thinning could widen or the flow of ice could change. Both would affect the rate at which the channel forms.

    “But the important point here is that Dotson is not a flat slab and it can be much thinner in places than we think it is and much closer to a stage where it might experience major change.”

    Dr Gourmelen’s new study, published in Geophysical Research Letters, uses the European Space Agency’s Cryosat and Sentinel-1 spacecraft to make a detailed examination of the thickness and movement of Dotson.

    The 70km by 40km ice shelf is the floating projection of two glaciers, Kohler and Smith. As they stream off the west of Antarctica, their fronts lift up and join together, pushing out over the Amundsen Sea.

    The shelf acts as a buttress to the ice behind. If Dotson were not present, Kohler and Smith would flow much faster, dumping more of their mass in the ocean, contributing to sea-level rise.

    Satellites have long tracked the behaviour of the shelf, but in Cryosat in particular researchers now have an altimeter instrument that is able to retrieve much higher-resolution elevation information than ever before.

    Taking the period of its observations from 2010-2016, Dr Gourmelen’s team can see that Dotson’s surface is lowering on average by about 26cm per year, which suggests the roughly 400m-thick shelf as a whole is thinning by about 2.5m per year.

    But Cryosat’s sharper vision also reveals that this thinning is concentrated at a surface depression that is roughly 5km wide and 60km long.

    It extends from the point where the glacier ice starts to float as it comes off the land, all the way out to the front edge of the shelf where icebergs are calved into the ocean.

    What the team is able to show is that this surface depression corresponds to an incised canyon on the underside of the shelf.

    The average width of this inverted gorge is 10-15km but it cuts up into the shelf by as much as 200m in places. The Edinburgh-led group says all the evidence suggests warm water from the deep ocean around Antarctica has got under the shelf to melt out the canyon.

    “We say warm; it’s 0.6-0.7 degrees,” explains Dr Gourmelen. “It makes its way into the cavity under the shelf along a trough to the grounding line, and then it starts to rotate clockwise and rises. And it comes out on the west side. That’s where we see the thinning and the basal melt.”

    This export of fresh melt-water from the underside of the shelf carries with it a lot of iron from rocks scraped from the continent, and drives strong growth in plankton and other biological activity in front of Dotson.

    Just a simple forward projection using the pattern and rates of thinning observed by Cryosat and Sentinel-1 in this study would lead to complete melt-through of Dotson’s front in 20 or so years, and its rear in about 40 years.

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  • @OP – Massive Iceberg’s Split Exposes Hidden Ecosystem

    The results of investigations should be appearing soon!

    Scientists will set out in the next week to study an Antarctic realm that has been hidden for thousands of years.

    A British Antarctic Survey-led team will explore the seabed ecosystem exposed when a giant iceberg broke away from the Antarctic Peninsula in 2017.

    The organisation has also released the first video of the berg, which covers almost 6,000 sq km.

    Its true scale begins to emerge in a shot filmed from an aircraft flown along its edge.

    An international team will spend three weeks, from February to March, on board the research ship RRS James Clark Ross, navigating ice-infested waters to reach the remote Larsen C ice shelf from which the berg calved.

    British Antarctic Survey marine biologist Dr Katrin Linse, who is leading the mission, said that the calving of the iceberg, which has been named A68, provides researchers with “a unique opportunity to study marine life as it responds to a dramatic environmental change”.

    “It’s important we get there quickly before the undersea environment changes as sunlight enters the water and new species begin to colonise,” she explained, adding that the mission was “very exciting”.

    Prof David Vaughan, science director at BAS stressed that it was a treacherous journey but said the team needed to “be bold”.

    “Larsen C is a long way south and there’s lots of sea ice in the area, but this is important science, so we will try our best to get the team where they need to be,” he said.

    “The calving of A68 offers a new and unprecedented opportunity to establish an interdisciplinary scientific research programme in this climate-sensitive region.
    Now is the time to address fundamental questions about the sustainability of polar continental shelves under climate change.”

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