Trillion-ton Antarctic iceberg calves, but don’t blame global warming

A one trillion ton iceberg – one of the biggest ever recorded – has calved away from the Larsen C Ice Shelf in Antarctica. The calving occurred sometime between Monday 10th July and Wednesday 12th July 2017, when a 5,800 square km section of Larsen C finally broke away. The iceberg, which is likely to be named A68, weighs more than a trillion tons.  Its volume is twice that of Lake Erie, one of the Great Lakes.

The final breakthrough was detected in data from NASA’s Aqua MODIS satellite instrument, which images in the thermal infrared at a resolution of 1km and confirmed by NASA’s Suomi VIIRS instrument.

The development of the rift over the last year was monitored using data from the European Space Agency Sentinel-1 satellites – part of the European Copernicus Space Component. Sentinel-1 is a radar imaging system capable of acquiring images regardless of cloud cover, and throughout the current winter period of polar darkness.

NASA Suomi VIIRS panchromatic image from July 12 2017, confirming the calving

The iceberg weighs more than a trillion tonnes (1,000,000,000,000 metric tonnes), but it was already floating before it calved away so has no immediate impact on sea level. The calving of this iceberg leaves the Larsen C Ice Shelf reduced in area by more than 12%, and the landscape of the Antarctic Peninsula changed forever.

Although the remaining ice shelf will continue naturally to regrow, Swansea researchers have previously shown that the new configuration is potentially less stable than it was prior to the rift.  There is a risk that Larsen C may eventually follow the example of its neighbor, Larsen B, which disintegrated in 2002 following a similar rift-induced calving event in 1995.

Professor Adrian Luckman of Swansea University, the lead investigator of the MIDAS project, said:

“We have been anticipating this event for months, and have been surprised how long it took for the rift to break through the final few kilometres of ice. We will continue to monitor both the impact of this calving event on the Larsen C Ice Shelf, and the fate of this huge iceberg.

The iceberg is one of the largest recorded and its future progress is difficult to predict. It may remain in one piece but is more likely to break into fragments. Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters.

The recent development in satellite systems such as Sentinel-1 and MODIS have vastly improved our ability to monitor events such as this.”

The Larsen C Ice Shelf, which has a thickness of between 200 and 600 metres, floats on the ocean at the edge of The Antarctic Peninsula, holding back the flow of glaciers that feed into it.

Researchers from the MIDAS Project have been monitoring the rift in Larsen C for many years, following the collapse of the Larsen A ice shelf in 1995 and the sudden break-up of the Larsen B shelf in 2002.  They reported rapid advances of the rift in January, May, and June, which increased its length to over 200 km and left the iceberg hanging on by a thread of ice just 4.5 km (2.8 miles) wide.

The team monitored the earlier development of the rift using a technique called satellite radar interferometry (SRI) applied to ESA Sentinel-1 images. While the rift is only visible in radar images when it is more than 50m wide, by combining pairs of images, SRI allows the impact of very small changes in ice shelf geometry to be detected, and the rift tip to be monitored precisely.

Dr. Martin O’Leary, a Swansea University glaciologist and a member of the MIDAS project team, said of the recent calving:

“Although this is a natural event, and we’re not aware of any link to human-induced climate change, this puts the ice shelf in a very vulnerable position. This is the furthest back that the ice front has been in recorded history. We’re going to be watching very carefully for signs that the rest of the shelf is becoming unstable.”

Professor Adrian Luckman of Swansea University added:

“In the ensuing months and years, the ice shelf could either gradually regrow, or may suffer further calving events which may eventually lead to collapse – opinions in the scientific community are divided. Our models say it will be less stable, but any future collapse remains years or decades away.”

Whilst this new iceberg will not immediately raise sea levels, if the shelf loses much more of its area, it could result in glaciers that flow off the land behind speeding up their passage towards the ocean. This non-floating ice would have an eventual impact on sea levels, but only at a very modest rate.

Read more at Project Midas

Comments (6)

  • Avatar

    Gary

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    Wow, this is cool! I hope we get to see some good photos tracking this amazing phenomenon. I wondered if it was ever going to happen and it finally did. That’s a big piece of ice, for sure. [are we evacuating Guam, yet? lololz]

  • Avatar

    Spurwing Plover

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    So how soon will it be until guam tips over? when is the british isle to become a series of teenie tiny islands? how soon will the last whale be heard? WHEN WILL THE ECO-STUPIDTY TO STOP? SQUAWK,SQUAWK,KRAAW,SKREE,SKREET

  • Avatar

    Jim

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    Excellent article that gives an unbiased report of the natural, not human induced break-up of the Larsen Shelf Area Sea Ice Segment “C”. I would add that natural geologically induced seafloor heat and chemically charged heated fluid flow are the likely root cause of this bottom sea ice melting phenomenon and eventual break-up.
    For instance, the division between Larsen Shelf Area Sea Ice Segments “A” and “B” is a 50 mile by 10 mile active volcanic plateau named the Seal Nunatak Island chain. It is home to 17 active or semi-active volcanoes some of which are seafloor volcanoes (Seamounts). The remaining land volcanoes almost certainly have large actively heat emitting seafloor fractures and seafloor hydrothermal vents (ocean floor hot geysers) associated with them. The Seal Nunatak volcanic plateau owes its very existence to geological activity associated with the 3,500 mile long West Antarctic Rift / Fault System. This rift is literally ripping the entire Antarctic Continent into two pieces, and in the process tapping deep Earth hot lava pockets that flow to the seafloor and continental bedrock. There are 61 currently erupting, active, or semi-active volcanoes along the rift.
    For more details see….http://climatechangedispatch.com/geologic-forces-fueling-west-antarcticas-larsen-ice-shelf-cracks, and here http://climatechangedispatch.com/antarcticas-larsen-ice-shelf-break-up-driven-by-geological-heat-flow-not-climate-change/

  • Avatar

    rakooi

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    ASIAN NEWS MEDIA
    is in near PANIC mode as their populations are able to SEE their own Ice & Snow Packs
    disappearing year by year, their primary source of water for drinking & irrigation.

    *
    “Mainstream Science” has known for decades that the rapid rise in Global temperatures was caused by greenhouse gases which were increasing in the atmosphere; interfering with the normal Infra Red Radiation/Energy emitted by earth & escaping to cold space.

    https://insideclimatenews.org/news/04052017/global-warming-hiatus-debunked-climate-science
    http://iopscience.iop.org/article/10.1088/1748-9326/11/4/048002

    In the EXACT WAVE LENGTHS of those greenhouse gases,
    escaping I.R. radiation is missing.
    Captured
    re-radiated toward earth (additional heating).

    US, Japan have satellites
    which provide a detail record of Digital Measures of that exact effect!
    *
    The Goldilocks amount of CO2 & other greenhouse gasses is between 250-300PPM .
    THAT Goldilocks Level of GHG has kept our climate/world temperatures in a range enabling humans to be fruitful and multiply.

    In eons past,
    Changes in Earth Orbit and Axis have Caused & ENDED Ice ages.
    WHILE CO2 did not cause these epochs, it was intimately linked to these most powerful of Natural Earth cycles.

    This Additional amount of warming on Earth, since the 1800’s has been largely IN SPITE of variations in solar energy output.
    Recently we have been in a weakened solar output & yet setting record hot year after record hot year.

    The Rapid Rise of CO2 / the Rise in world TEMPERATURES
    This phenomenon provides a ” near-perfect ” fit with
    both the timing and the nature of the increase.

  • Avatar

    Sonnyhill

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    Goldilocks is a fairy tale, don’t you know? So….now that we’re above 400 ppm CO2, humans are no longer fruitful or multiplying? You’re posting propaganda on a website dedicated to fighting green brain washing. Why are you wasting your time? Because you’ve been brain washed.

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