Mysterious rock-covered iceberg found near Barrow
August 10th, 2012 | Carey Restino
When Richard Glenn and Craig George heard a report from a seal tagging team that there was a large piece of ice north of Point Barrow with "rocks on it," their response was immediate.
"I mentioned it to Richard and he said, 'Get in the boat, let's go,'" said George, adding that they really didn't think they would find it when they set off July 29 but Richard recognized the significance .
But, as it turned out, the large piece of ice was exactly where the seal team had said it was, about 12 nautical miles northeast of Point Barrow - meaning it was likely grounded in more than 80 feet of water. And it was very unusual indeed.
George, Glenn and several others who came along found a 230-by-660-foot iceberg that was about 25 feet above the sealine on one face. It was covered with striations and rocks, suggesting it might well have been part of a glacier. The ice had long streaks in it and one end was covered with angular rocks and granite boulders unlike anything found anywhere near Barrow.
The duo's reaction when they saw it?
"It was very adolescent," George said, who has been a wildlife biologist in the region for more than 30 years. "That pretty much sums it up."
"I was like a kid in a candy store," said Glenn, who has studied geology and sea ice extensively. "It was pretty wild to see these beautiful? granite boulders."
The group was able to anchor up to the east side of the floe, which was mostly flat on top. Describing what they saw in a written summary, George noted that the surface of the floe was "smooth and striated with furrows and bands similar to a glacier. Some of the furrows appeared to represent sediment-laden bands in the ice. In other places, rocks and pebbles were 'meting in' to the ice surface."
The group observed 1,000s of rocks, with the largest rock some 4 foot (1.5 meters) cubed. The rocks were mostly granite.
"I've studied rocks for a long time and you just don't see rocks like that around here," Glenn said. "The oil bearing rocks of the North Slope are the sedimentary type."
So where did the floe with its unusual rocks come from? George and Glenn sent photos to scientists in Canada and elsewhere. The initial theory is that the chunk of ice may be part of an "ice shelf" or glacier, perhaps in the northeastern Canadian Arctic Islands where glaciers that were previously ice-bound are now on open water. Perhaps a chunk calved off and entered what Glenn describes as a circular clockwise current flow that characterizes the Arctic Ocean's circulation pattern.
While it is unusual to see an ice floe with boulders on it from far-away terrain, it's not unheard of. While neither Glenn nor George has ever seen anything like this before in all their years of traveling and studying the Arctic, Inupiat elders they have talked to have said such floes sometimes float through - usually farther from shore.
In addition, there are areas in the Arctic landscape and nearshore waters where similar boulders can be found, boulders that show evidence of glaciation despite the fact that no such glaciation occurred in the Barrow?? area. It's possible those boulders came to rest on shore after hitching a ride on a chunk of ice, too.
George said that this floe may also be an indication of the changes due to climate shifts and the opening of waters in the Arctic that would allow this piece of ice to be castaway from the Canadian Arctic and drift along the US arctic coast.
"We speculate that reduced multiyear ice cover in the Chukchi (and polar pack in general) may allow previously icebound glacial fragments such as this to more easily enter the surface circulation of the Arctic Ocean and come to rest on the nearshore waters of the Chukchi and Beaufort seas," George wrote. "But the scientists who study these ice formations will soon give us a clearer answer."
An ice fragment estimated at some 55 feet above the sealine was spotted in May off Point Belcher north of Wainwright, which also appeared to be glacial ice.
"It's a current and clear example of what's happening over time," said Glenn.
Carey Restino can be reached at firstname.lastname@example.org.