Shock News – Massive Calving of Jakobshavn Isbræ

We reported on similar “Shock News” back in February 2015, and now it’s happened again.

Here is a large animation of recent events at the Jakobshavn Glacier calving front, courtesy of Espen Olsen at the Arctic Sea Ice Forum.

Click to view the ~5 Mb file at full resolution:

[Edit – May 6th]

In the absence of further input from the somewhat “skeptical” commenter below, here is an extract from one of the “~1420 recent academic articles” referred to. Namely “Bed elevation of Jakobshavn Isbrae, West Greenland, from high-resolution airborne gravity and other data: Bed topography of Jakobshavn Glacier” by Lu An, Eric Rignot et al.:

Jakobshavn Isbræ, West Greenland, which holds a 0.6 m sea level volume equivalent, has been speeding up and retreating since the late 1990s. Interpretation of its retreat has been hindered by difficulties in measuring its ice thickness with airborne radar depth sounders. Here we employ high-resolution, helicopter-borne gravity data from 2012 to reconstruct its bed elevation within 50 km of the ocean margin using a three-dimensional inversion constrained by fjord bathymetry data offshore and a mass conservation algorithm inland.

We find the glacier trough to be asymmetric and several 100 m deeper than estimated previously in the lower part. From 1996 to 2016, the grounding line migrated at 0.6 km/yr from 700 m to 1100 m depth. Upstream, the bed drops to 1600 m over 10 km then slowly climbs to 1200 m depth in 40 km.

Jakobshavn Isbræ will continue to retreat along a retrograde slope for decades to come.

Watch this space!

10 thoughts on “Shock News – Massive Calving of Jakobshavn Isbræ

  1. Calving happens when there is too much ice.

    These Glacier are not melting away they are being eroded under water because of a lot of ice production.

    Not a shocking news, more like FUD.

      1. Jim, the OP writes with such authority on the calving of Jakobshavn Isbræ, I am confident he’s discovered the problem:

        The glacier is simply producing too much ice.

        1. Well David, Greenland adds some 600 gigatons of ice annually, and there is such a thing as the ‘angle of repose’, so you would expect, as mountaineer does, some shedding of ice and seaward motion over time. How excessive it is would be a matter for the researchers (and catastrophe skeptics) to argue.

          1. Well Taylor,

            “Greenland adds some 600 gigatons of ice annually”?

            No it doesn’t. Are you by any chance thinking of just the Surface Mass Balance?

            When it comes to the total mass balance including the “shedding of ice” of which you speak see:

          2. Of course, Surface Mass Balance is the ice that’s being ‘added’, Jim. Here’s how Wikipedia describes it, quoting from the 3rd IPCC report:
            “ The IPCC Third Assessment Report (2001) estimated the accumulation to 520 ± 26 Gigatonnes of ice per year, runoff and bottom melting to 297±32 Gt/yr and 32±3 Gt/yr, respectively, and iceberg production to 235±33 Gt/yr. On balance, the IPCC estimates −44 ± 53 Gt/yr, which means that the ice sheet may currently be melting.[2] Data from 1996 to 2005 shows that the ice sheet is thinning even faster than supposed by IPCC. ”

            When I said 600gt added, I’m referring to the first parameter the IPCC cites, and it varies year to year. That’s why they found a WW II plane buried in over 200 feet of ice. The other two parameters vary yearly as well, leading to net gains or losses in annual ice volume. Lately it’s losses, but a minuscule fraction of the total ice sheet. There’s so evidence that current losses are not unprecedented in recent history (for example, in the 30s and 40s when high temperature records were set).

          3. 2001 is a long time ago Taylor! The IPCC Sixth Assessment Report is not too far off now, and you quote Wikipedia at me?!

            I’ve already provided you with some much more recent data, so why don’t you discuss that?

            According to your reference “The [Greenland] ice sheet is thinning even faster than supposed by IPCC.”!

  2. Thanks, Taylor. Note that I was reacting to mountaineer’s fact-free post. And yes, Greenland is losing ice at an alarming rate at any angle.

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