Earth Matters

Famous Rectangular Iceberg’s Rough Journey

November 5th, 2018 by Kathryn Hansen
This wide view, acquired on October 14, 2018, by the Landsat 8 satellite, shows the area where part of the rectangular iceberg was photographed from NASA’s DC-8. Credit: Christopher Shuman (NASA GSFC/UMBC JCET), using Landsat data from the U.S. Geological Survey.

This rectangular iceberg made headlines after it was photographed on October 16, 2018, during an Operation IceBridge science flight. Credit: NASA/Jeremy Harbeck

The sharp-angled iceberg that made headlines in late October 2018 had a longer, rougher journey than was initially thought.

The iceberg was spotted on October 16, 2018, during a flight for Operation IceBridge—NASA’s long-running aerial survey of polar ice. During that day’s survey of glaciers and ice shelves along the northern Antarctic Peninsula, scientist Jeremy Harbeck spotted the compelling berg. Harbeck explained in a NASA story his reason for taking the picture:

“I was actually more interested in capturing the A68 iceberg that we were about to fly over, but I thought this rectangular iceberg was visually interesting and fairly photogenic, so on a lark, I just took a couple photos.”

Not only were the edges of the iceberg extremely straight, but the two corners appeared “squared off” at right angles. The berg was so clean-cut that it was reasonable to assume it might have very recently calved from the Larsen C ice shelf. That’s the same ice shelf that spawned A-68, the trillion-ton iceberg that broke away in July 2017.

It turns out, however, that the rectangle berg actually has had a much longer journey. Scientists used images from Landsat 8 and the European Space Agency’s Sentinel-1 to trace the berg back to its origins. They found that it calved from the ice shelf’s new front in early November 2017, just a few months after A-68 broke away. The image below, tweeted November 9, 2018, by Stef Lhermitte of Delft University of Technology, shows the small, newly calved icebergs. The rectangle iceberg—which was about 4 kilometers long at the time—appears just north of a curved berg. Both were about a third of the way down the new front of the Larsen C.

The rectangle berg then began a northward journey, navigating the newly open water between the Larsen C ice shelf and Iceberg A-68. Collision threats were everywhere: A-68 could smash into the little bergs at any time, and smaller bergs could collide with each other.

The berg cruised all the way north and through a narrow passage between the A-68’s northern tip and a rocky outcrop near the ice shelf known as Bawden Ice Rise. NASA/UMBC glaciologist Chris Shuman likens this zone to a nutcracker. A-68 has repeatedly smashed against the rise and caused pieces of ice to splinter into clean-cut geometric shapes. An area of geometric ice rubble is visible in the Landsat 8 image (top and below) from October 14, 2018, two days before the IceBridge flight.

The once-long rectangle berg did not make it through unscathed; it broke into smaller bits. The iceberg in Harbeck’s photograph, circled in the annotated Landsat 8 satellite image, appears closer to the shape of a trapezoid. The trapezoidal berg is about 900 meters wide and 1500 meters long, which is tiny compared to the Delaware-sized A-68.

By November 2018 the iceberg had moved out of the rubble zone and into open water. Shuman noted: “Now it’s just another iceberg on its way to die.”

2 Responses to “Famous Rectangular Iceberg’s Rough Journey”

  1. Mark Price says:

    So how far had the ice berg traveled when it was spotted Oct. 16 of this year?
    And in this sentence, do you mean 2017? “The image below, tweeted November 9, 2018, by Stef Lhermitte of Delft University of Technology, shows the small, newly calved icebergs.”

  2. Christine Sutton says:

    That’s it? I was hoping for some explanation! This article doesn’t say how this rectangular shape happened…