Petermann's 76-square-kilometer ice island survived its first collision intact
The August berg was the largest Arctic calving since 2020, but it broke along a fracture the team watching Petermann had not expected, leaving two rifts that together outline more than twice the area that left.
The Scientist · Science desk
What happened
- The berg that broke from Petermann Glacier on Greenland's northwest coast in August was roughly the size of St. Thomas in the U.S. Virgin Islands and the largest calving by any Arctic glacier since 2020.
- It was the largest ice island off Petermann since the 130-square-kilometer slab of 2012, which itself followed events of 31 square kilometers in 2008 and just over 250 square kilometers in 2010.
- The ice let go along a different fracture than the rift the University of Ottawa team had been monitoring, which is why the resulting island came out smaller than they had anticipated.
- Drifting about 3 kilometers a day, the island rammed Joe Island, a rocky outcrop at the fjord's junction with Nares Strait, in an encounter caught by Landsat 9 on August 23 and 24.
- Wind and surface currents then swept it clear of the fjord, and satellite images show it pivoting away from Joe Island and continuing southwest through Nares Strait.
Why it matters
- Who's exposed exposure Because the slab left the fjord in one piece rather than shattering at the first obstacle, its eventual fragments carry downstream, and Garbo's group notes that ice islands travel far enough to reach marine activity and infrastructure while spreading freshwater as they melt.
- What's now possible capability Petermann is now one of the few places where the size of the next two calvings can be estimated in advance from imagery of existing cracks, even though the timing cannot be.
- What it limits constraint If the Akesson paper NASA cites is right that the shelf may not recover after a future breakup, then area subtracted from the tongue is a running total rather than a cycle, and treating any single event as routine offers less reassurance than it seems.
- Who has to decide decision For groups deciding where to put continuous observation rather than event-driven attention, the gatekeeper role NASA assigns Petermann is the argument, and it rests on ice behind the tongue rather than the berg in the strait.
The glacier still carries a more telling number than the berg that left it. Two large rifts were still crossing Petermann's floating tongue in late August, and the researchers tracking them expect islands of roughly 94 and 84 square kilometers when they finally cut through, on timing nobody can pin down [8]. Together that is about 178 square kilometers of tongue already outlined by cracks, roughly 2.3 times the area that left this summer [19]. Adam Garbo, the University of Ottawa glaciology doctoral student who spotted the break in Sentinel-1 imagery on August 4, has been using remote sensing to follow the tongue with an international team [4].
Calving by itself is ordinary. NASA's account treats it as a routine part of an outlet glacier's life cycle and says researchers watch the process alongside other observations for longer-term signs of instability [6]. Petermann earns that attention because it is one of Greenland's largest marine-terminating glaciers and acts as a gatekeeper for ice moving from the ice sheet into the ocean, which is where the sea-level relevance actually sits [5]. Among the references NASA lists is a 2022 Nature Communications paper by Akesson and colleagues concluding that the Petermann ice shelf may not recover after a future breakup [18]. If that holds, the ledger worth keeping is cumulative area off the tongue rather than the size of any one berg. The four large events since 2008 come to roughly 487 square kilometers [22].
The collision doubled as a physical test. Joe Island sits at the mouth of the fjord, one of the first obstacles a departing island meets, and a collision there split the 2010 ice island in two [11]. This one was estimated at less than 150 meters thick [13], and Mauri Pelto of Nichols College notes that Petermann bergs tend to be thinner and more fragile than those calved by Jakobshavn or Helheim, thinner still than Antarctica's [15]. Garbo said the team was impressed that it came away without further fragmentation [12]. Survival at that scale means the outline held; whatever the impact did internally will only show as tides, winds, currents and melting take the island apart on its way southwest [14].
Two gaps remain in the record. The only drift rate reported is 3 kilometers per day, averaged over the first week after calving [9], while 19 days separate the August 4 detection from the Landsat 9 image of the collision [21]. And at 76 square kilometers with a thickness estimate under 150 meters, the island contains at most about 11 cubic kilometers of ice [20], an upper bound resting on an estimated thickness rather than a measured one.
What to watch
- Whether either remaining rift cuts through, and whether the resulting island matches the roughly 94 and 84 square kilometer estimates.
- Whether the island breaks up in Nares Strait or grounds later in its drift, as previous Petermann ice islands have off Coburg and Baffin islands.
- Any measured change in the ice tongue's speed after the August loss, which would say more about buttressing than the berg's area does.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence62
- Adoption
- Not scored
- Hype gap0
- Incentives
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- Confidence66
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
A berg that broke from Petermann Glacier along Greenland's northwest coast in August was roughly the size of St. Thomas in the U.S. Virgin Islands and was the largest calving event by any Arctic glacier since 2020.
- [2]
The team reported that the large tabular iceberg, or ice island, measured just over 76 square kilometers (29 square miles) at the time it calved.
- [3]
It was the largest to break from Petermann since the ice island of 2012, which measured 130 square kilometers; earlier major events came in 2008 (31 square kilometers) and 2010 (just over 250 square kilometers).
- [4]
The calving was spotted on August 4 by Adam Garbo, a doctoral student in glaciology at the University of Ottawa, in imagery from the European Space Agency's Sentinel-1 mission; Garbo and an international team have been using remote sensing to study and track the glacier's ice tongue.
- [5]
Petermann is one of Greenland's largest marine-terminating glaciers and acts as a gatekeeper for ice flowing from the ice sheet into the ocean; its future stability has implications for sea level rise.
- [6]
Iceberg calving is a routine part of an outlet glacier's life cycle, and scientists watch the process closely along with numerous other observations of the ice and its environment for longer-term signs of instability.
- [7]
Garbo and colleagues had expected a major calving once one of the large rifts they were monitoring cut all the way across Petermann's ice tongue; Garbo said the calving instead followed a different fracture, producing a smaller ice island than they had originally anticipated.
- [8]
As of late August, two large rifts remained and were expected to eventually produce new ice islands of roughly 94 square kilometers and 84 square kilometers, though the timing remained uncertain.
- [9]
Glaciologist Mauri Pelto of Nichols College tracked the iceberg using NASA-USGS Landsat imagery as it drifted down Petermann Fjord toward Nares Strait; in the week since it calved, the berg drifted an average of 3 kilometers per day.
- [10]
The berg rammed into a small rocky outcrop known as Joe Island at the fjord's junction with Nares Strait, an encounter visible in images captured by the Operational Land Imager on Landsat 9 on August 23 and August 24.
- [11]
Joe Island sits at the mouth of Petermann Fjord, making it one of the first obstacles a departing ice island meets, and collisions with it, like the one that split the 2010 ice island in two, often mark the start of a berg's breakup.
- [12]
Garbo said the team was watching closely as the island interacted with Joe Island and was impressed that it survived the interaction without further fragmentation.
- [13]
The ice island was estimated to be less than 150 meters thick at the time of calving.
- [14]
Wind and surface currents have swept the island out of the fjord, and satellite images show it pivoting away from Joe Island and continuing southwest through Nares Strait, where it will fracture into smaller pieces as tides, winds, currents and melting weaken the ice.
- [15]
Pelto noted that Petermann bergs tend to be thinner and more fragile than those calved by glaciers such as Greenland's Jakobshavn and Helheim, and thinner still than Antarctica's.
- [16]
Thicker bergs that calve from tidewater glaciers without floating ice-shelf extensions can drag and even become grounded on the seafloor within the fjord, while ice islands like Petermann's might run aground later in their drift; many ice islands have become grounded off the coasts of Coburg and Baffin islands.
- [17]
Garbo and colleagues noted that ice islands and their fragments have been known to travel considerable distances, posing potential hazards to marine activities and infrastructure while also distributing freshwater through the ocean as they melt.
- [18]
Among the references listed with the NASA account is Akesson, H., et al. (2022), "Petermann ice shelf may not recover after a future breakup," Nature Communications, 13(2519).
- [19]
The two rifts still crossing the tongue in late August outline about 178 square kilometers of ice, roughly 2.3 times the area of the August calving.
- [20]
At just over 76 square kilometers and a thickness estimated below 150 meters, the island holds at most about 11 cubic kilometers of ice.
- [21]
Nineteen days separate the August 4 detection of the calving from the August 23 Landsat 9 image of the collision with Joe Island.
- [22]
The four large Petermann calving events since 2008 total roughly 487 square kilometers.
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Sources
1 independent publisher whose own reporting we read for this story.
- nasa.govIce Island Survives Run-In With Joe Island
1 article · August 31, 2026
- phys.orgIce island survives run-in with Joe Island
1 article · September 1, 2026
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Topics
- Greenland Ice SheetFollow
- Satellite Remote Sensing MissionsFollow
- Sea-level riseFollow
- Iceberg CalvingFollow
Entities
- Landsat 9Follow
- Nichols CollegeFollow
- Copernicus Sentinel-1Follow
- Nares StraitFollow
- Petermann GlacierFollow
- Adam GarboFollow
- European Space AgencyFollow
- NASA Earth ObservatoryFollow
- Mauri PeltoFollow
- University of OttawaFollow
- Joe IslandFollow