Tag Archives: Nares Strait

Land-Fast Ice Cover off North Greenland: Will NASA bite?

When a large outlet glacier of North Greenland (Petermann Gletscher) discharged an ice island four times the size of Manhattan in August of 2010, the United States’ Congress held formal inquiries on its cause within days of the event. Congressmen, scientists, and the global media speculated that this event and concurrent severe droughts in Russia and floods in Asia were tied to record-breaking air temperatures and global warming. Reviewing available data, Johnson et al. (2011) cautioned that most melting of floating ice shelves such as Petermann Gletscher is dominated by physical ocean processes below, not above the ice (Reeh, 2001, Rignot and Steffen, 2008). The National Journal asked me to write an essay to answer the question: “Is Climate Change Causing Wild Weather?” which I answered with a nerdy No, but …. Motivated by questions asked during the congressional hearing, I showed that waters in Petermann Fjord (a) originate from the Arctic Ocean to the north, (b) contain heat of Atlantic origin, and (c) have warmed significantly since 2003 (Muenchow et al., 2011).

Petermann Gletscher from MODIS Terra. Repeat NASA along-glacier flight tracks are shown in the left and middle panels. White line across the glacier are ICESat tracks. Thick black line across the glacier near y = 0 km is the grounding line location from Rignot and Steffen (2008). Dark areas within 2 km off the western wall are mountain shadows.

Petermann Gletscher from MODIS Terra. Repeat NASA along-glacier flight tracks are shown in the left and middle panels. White line across the glacier are ICESat tracks. Thick black line across the glacier near y = 0 km is the grounding line location from Rignot and Steffen (2008). Dark areas within 2 km off the western wall are mountain shadows.

When I reported here that the same glacier discharged yet another ice island in July 2012, this one “only” twice the size of Manhattan, I was not so sure anymore, that this was merely another extreme event caused by natural processes. Continue reading

Petermann Photos, Places, and People

Petermann Gletscher sent off Manhattan-sized islands of ice in 2010 and 2012 that now litter the eastern seaboard of Canada from its farthest northern Ellesmere Island to its farthest eastern Newfoundland. The ice is streaming south along thousands of miles within icy Arctic waters. Petermann Gletscher itself is flat, hard to grasp by the naked eye, its endless expanse of white vanishes into the horizon when we look towards the Greenland Ice Sheet ALONG the glacier:

North-eastern section of Petermann Glacier on Aug.-11, 2012, the meandering river is the centerline, view is almost due east. [Photo Credit: Canadian Coast Guard Ship Henry Larsen.]

North-eastern portion of Petermann Glacier on Aug.-11, 2012, the meandering river is the centerline, view is almost due east with Kap Fulford and Kap Agnes on the left center and Daugaard Jensen Land in the background on the right. [Photo Credit: Canadian Coast Guard Ship Henry Larsen.]

Next, lets look ACROSS Petermann from roughly the same latitude. This perspective is more dramatic as vertical cliffs give shape, cliffs are cut by smaller side-glaciers. More specifically, we see the CCGS Henry Larsen helicopter flying down Belgrave Glacier as we look across Petermann which flows from the Greenland Ice Sheet on the left out to sea on the right. On the other (south-western) side we see Faith Glacier in the background about 10 miles away.

Seaward front of Petermann Glacier Aug.-11, 2012. View is from a small side-glacier towards the south-east across Petermann Fjord with Petermann Gletscher to the left (east). [Photo Credit: Erin Clarke, Canadian Coast Guard Ship Henry Larsen]

Seaward front of Petermann Glacier Aug.-11, 2012. View is from a small side-glacier (Belgrave Gl.) towards a similar glacier (Faith Gl.) across Petermann Fjord with Petermann Gletscher flowing from the left out to sea on the right. [Photo Credit: Erin Clarke, Canadian Coast Guard Ship Henry Larsen]

Contrasting large Petermann Gletscher, the many smaller glaciers on both its sides evoke drama as ice plunges down from 3000 feet above in a rage of forms, colors, and shapes. These side glaciers have their own side glaciers that sometimes rival the Alpine glaciers in Europe, Asia, and the Americas that most of us are more familiar with.

Some side glaciers have names, but they are rarely seen on maps and charts. The side glaciers are mapped, but photos are hard to find. Flying over them last year, I was utterly lost. Reviewing photos now, I remember people, smells, computer troubles, and exciting ocean discoveries. Nevertheless, I am hard pressed to place the places we saw on a map or name them. Distances are deceiving, the air is clean and 50-80 miles of visibility are common. A moment later, I cannot see the other side of the ship as we are suddenly in clouds and fog. Everything is always in motion, the ice, the water, the ship, the clouds, all of this without strong reference points like the exit or distance signs on a Turnpike, Interstate, or Autobahn.

Northern Kennedy Channel near the entrance to Petermann Fjord with Kap Morton in cloud banks. [Credit: Andreas Muenchow]

Northern Kennedy Channel near the entrance to Petermann Fjord with Kap Morton in cloud banks. [Credit: Andreas Muenchow]

And along comes Espen Olsen, a frequent contributor to Neven’s Arctic Sea Ice blog and forums, and discovers a plethora of names that I can check, google, and use to remember expeditions to Petermann over the last 10 years with many good friends. So with his help and that of other explorers like Lauge Koch, Tony Higgins, and the collected wisdom of the U.S. Defense Mapping Agency, I labeled some prominent glaciers and capes on an Aug,-21, 2012 MODIS-Terra image that I constructed from data that NASA provide to anyone free of charge. I chose this image and time, because the 2012 ice island is already in Nares Strait and thus out of sight:

Names of glaciers, capes, islands in Petermann Region over MODIS of Aug.-21, 2012.

Names of glaciers, capes, islands in Petermann Region over MODIS of Aug.-21, 2012.

Espen tells me that his Danish sources are protected by copyright (I still like to cite them), but the aviation maps of the U.S. military are in the public domain and can be downloaded from the University of Texas in Austin Library, e.g.,

Petermann Gletscher and surroundings extracted from U.S. Defense Mapping Agency Chart ONC A5 (January 1991).

Petermann Gletscher and suroundings extracted from U.S. Defense Mapping Agency Chart ONC A5 (January 1991).

while the modified version of Figure-2 from Dr. Tony Higgins 1990 publication is available at the Alfred Wegener Institute. Nevertheless, it should only be used for non-profit educational purposes or as a reference:

Petermann Gletscher extend and topography from 1953 through 1978 (from Higgins, 1990) with 2012 terminus position drawn in by hand.

Petermann Gletscher extend and topography from 1953 through 1978 (from Higgins, 1990) with 2012 terminus position drawn in by hand.

With all these details out-of-the-way, we can now start placing photos into places and add names to them. Perhaps others like Espen Olsen can write or edit Wiki entries or correct the false latitude and longitudes that populate the many databases that provide such information on the web. Over the next weeks and months I will try to post as many photos of Petermann’s natural beauty along with an evolving MODIS map that names and shows places. Here are just a few teasers without further comment except what’s in the captions.

The merging of Sigurd Berg and Hubert Glaciers which discharge into Petermann Gletscher on its eastern wall. The view is landward towards the north-east as the helicopter flies in from Petermann. [Credit: Barbara O'Connell, Canadian Coast Guard]

The merging of Hubert (left) and Sigurd Berg (right) Glaciers which discharge into Petermann Gletscher on its eastern wall. The view is landward towards the north-east as the helicopter flies in from Petermann. [Credit: Barbara O’Connell, Canadian Coast Guard]

Petermann Gletscher and Fjord in Aug.-2012. View is to the north-west with Faith Glacier (top left) and Kap Lucie Marie (top right) showing the western wall of Petermann. [Photo Credit: CCGS Henry Larsen]

Petermann Gletscher and Fjord in Aug.-2012. View is to the north-west with Faith Glacier (top left) and Kap Lucie Marie (top right) showing the western wall of Petermann. [Photo Credit: CCGS Henry Larsen]

Looking down Belgrave Glacier discharging into Petermann Gletscher at its terminus in Aug. 2012 [Credit: CCGS Henry Larsen]

Looking down Belgrave Glacier discharging into Petermann Gletscher at its terminus in Aug. 2012 [Credit: CCGS Henry Larsen]

Higgins, A.K. (1990). Northern Greenland glacier velocities and calf ice production Polarforschung, 60, 1-23 Other: 0032-2490

Shades of White as the Sun Rises over Nares Strait

After four months of total darkness the sun is back up in Nares Strait. It transforms the polar night into thousand shades of white as mountains, glaciers, and ice take in and throw back the new light. Our satellites receive some of the throw-away light as the landscape reflects it back into space. During the long dark winter months these satellites could only “see” heat, but this will change rapidly as Alert atop of Arctic Canada receives 30 minutes more sun with each passing day.

Surface temperature in degrees centigrade over northern Baffin Bay on March-4, 2013 16:20 UTC from MODIS Terra.

Surface temperature in degrees centigrade over northern Baffin Bay on March-4, 2013 16:20 UTC from MODIS Terra. Warm colors (reds) show thin and/or ice while cold colors (blues) suggest thick ice stuck in place.

A very strong ice arch at the southern entrance to Nares Strait separates thick (and cold) ice to north from thin (and warm) ice to the south. The thick and cold ice is not moving, it is stuck to land, but the ocean under the ice is moving fast from north to south. The ocean currents thus sweep the newly formed thin ice away to the south. This ice arch formed way back in early November just after the sun set for winter over Nares Strait.

Now that the sun is up, we can also “see” more structures in the ice by the amount of light reflected back to space. A very white surface reflects lots while a darker surface reflects less. We are looking at the many shades of white here … even though I color them in reds and blues:

Surface reflectance at 865 nm in northern Baffin Bay on March-4, 2013 16:20 UTC from MODIS Terra.

Surface reflectance at 865 nm in northern Baffin Bay on March-4, 2013 16:20 UTC from MODIS Terra. A true color image (which this is not) would show only white everywhere. Hence I show the very bright white as red and the less bright white as blue. This artificial enhancement makes patterns and structures more visible to the eye.

Zooming into the area where the ice arch separates thick ice to the north that is not moving from thin ice in the south that is swept away by ocean currents, I show this image at the highest possible resolution:

Surface reflectance at 865 nm at the southern entrance to Nares Strait on March-4, 2013. Contours are 200-m bottom depth showing PII2012 grounded at the north-eastern sector of the ice arch.

Surface reflectance at 865 nm at the southern entrance to Nares Strait on March-4, 2013. Contours are 200-m bottom depth showing PII2012 grounded at the north-eastern sector of the ice arch.

Note, however, that the sun is far to south and barely peeking over the horizon. This low sun angle shows up as shadows cast by mountains. And since the sun is still far to the south, the shadows cast are to the north. This “shadow” makes visible the ice island from Petermann Gletscher that anchors this ice arch as it is grounded. I labeled it PII2012 in the picture.

From laser measurements we know that the ice islands stands about 20 meter (or 60 feet) above the rest of the ice field. This height is enough to cast a visible shadow towards the north (slightly darker = less red) as well as a direct reflection off its vertical wall facing south (brighter = more red) towards the sun. At its thickest point, PII2012 is about 200 meters (~600 feet) thick. For this reason, I also show the 200-m bottom contour that moves largely from north to south along both Ellesmere Island, Canada on the left and Greenland on the right.

The sun brings great joy to all, especially those hardy souls who live in the far north. The sun’s rise also shows the delicate interplay of light and shadows that we can use to solve puzzles on how ice, oceans, and glaciers work. At the entrance of Nares Strait the playful delights of the sea ice, ocean currents, and ice islands gives us a large area of thin ice. The thin ice will soon melt and perhaps has already started to set into motion a spring bloom of ocean plants. Ocean critters will feed on these to start another cycle of life. Whales, seals, and polar bears all depend on it for 1000s of years now.

Sketch of the biological pieces that a large area of open water near a fixed ice edge like that of a polynya may support. [From Northern Journal>/a>]

Sketch of the biological pieces that a large area of open water near a fixed ice edge like that of a polynya may support. [From Northern Journal]

Did I ever see a Polar Bear?

When people hear that I have worked as a physical oceanographer in the Arctic for almost 20 years, their first question is often: “Did you ever see a Polar Bear?” The answer is a yes, but when we see bears, it is usually as a tiny moving speck of yellowish white near the white, icy, and hazy horizon. Only twice was it different. The first time was in October 2003 to the north-west off Arctic Alaska when a young bear swam towards and around the U.S. Coast Guard Cutter Healy doing station work:

Polar Bear seen Oct.-10, 2003 from aboard the USCGS Healy to the north-east of Alaska [Credit: Andreas Muenchow, University of Delawarel]

Polar Bear seen Oct.-10, 2003 from aboard the USCGC Healy to the north-east of Alaska [Credit: Andreas Muenchow, University of Delaware]

The second close encounter was last year as the Canadian Coast Guard Ship Henry Larsen was about to leave Nares Strait on Aug.-12. Out of the 100+ pictures snapped of this bear, the ship’s Steward Kirk McNeil of Labrador probably took the best shot:

Polar bear as seen in Kennedy Channel on Aug.-12, 2012. [Photo Credit: Kirk McNeil, Labrador from aboard the Canadian Coast Guard Ship Henry Larsen]

Polar bear as seen in Kennedy Channel on Aug.-12, 2012. [Photo Credit: Kirk McNeil, Labrador from aboard the Canadian Coast Guard Ship Henry Larsen]

This bear approached the drifting ship leisurely over a 10 minutes period from a large piece of ice that also drifted with the tides and currents. My PhD student Pat Ryan captured the last 2 minutes of this visit with her iPhone. The voice is hers (I also discern the voice of Ice Specialist Erin Clarke). Greenland is in the background to the east:

ADDENDUM Feb.-13, 2013: I just found this map of the spatial distribution of polar bears from a Dec.-23, 2012 article in the Washington Post by Juliet Eilperin entitled “Polar bear trade, hunting spark controversy.” Writing for the Wall Street Journal Feb.9, 2013, Zac Unger commented with the question “Are polar bears really disappearing?”

Polar bear population and their trends. [Source: Polar Bear Specialist Group. Laris Karklis/The Washington Post. Published on December 23, 2012, 5:24 p.m.]

Polar bear population and their trends. [Source: Polar Bear Specialist Group. Laris Karklis/The Washington Post. Published on December 23, 2012, 5:24 p.m.]

Addendum Feb.-25, 2013: A very funny bear commercial.

Nares Strait Ice Arches and Petermann Ice Island 2012

Arching barriers of ice locked solidly to land are presently closing off Nares Strait for all ice leaving or entering this ocean passage from the Arctic to the North Atlantic Oceans. Gothic cathedrals have flying buttressing to hold them in place while ice arches have buttressing land that keeps them stable. The sea ice becomes land-fast until these ice arches collapse in June or early July. As the ocean under the ice is still moving, generally from north to south, one often finds very thin ice or even open water to the immediate south of these ice arches. Some of these temperature signals let us “see” large ice structures even in the dark of night which in Nares Strait lasts from early October to late March.

Surface temperature in degrees Celsius for Nares Strait on Nov.-10, 2012 from MODIS Terra. Thick ice is blue (cold) while thin ice is red (warm).

Surface temperature at the northern entrances to Nares Strait with the Arctic Ocean to the north.

Surface temperature at the southern entrance of Nares Strait with the North Atlantic Ocean to the south.

Southern entrance of Nares Strait as seen from RADARSAT showing ice arch formation in more spatial detail than MODIS temperatures do. Note the embedded ice island PII-2012 from Petermann Gletscher at the north-eastern edge of the ice arch. [Credit: Luc Desjardins, Canadian Ice Service]

These ice arches usually form in December or January, but this year they form a little earlier than usual. In some years such as 2006/07 or 2009/10 and 2010/11 they did not form at all and thick multi-year ice left the Arctic via a passage that is now closed. This leaves only Fram Strait to the east of Greenland for such export this year.

It appears that the large ice island that broke free from Petermann Gletscher earlier this year provides some stabilizing support to the southern ice arch as it is anchoring its north-eastern corner where it is possibly grounded. The depth of the ice island PII-2012-A1 is about 180 to 200 meters thick. I derived this estimate from both NASA’s Airborne Topographic Mapper (ATM) and the University of Kansas’s Radar Depth Sounder both flown concurrently on a DC-8 plane that surveyed Petermann Gletscher on May-7, 2011 with PII-2012-A1 still attached:

Profile of Petermann Glacier from laser (red) and radar (black) measurements on May-07, 2011. The 2012 break-up is indicated by a spike of the red under-ice topography near km-22. Bottom profiles from laser assume hydrostatic balance of floating ice.

The ATM is a scanning laser that measures the distance from the DC-8 to the surface within 0.2 meters (about 6-7 inches). If I know both the true sea level surface (I do, it’s called the geoid) and if the ice is floating undisturbed, then I can convert the surface elevation into a bottom draft. The red curve outlines the “theoretical” bottom of the glacier. This curve is masked by a thicker black curve that is a radar-derived image of the under-side of the glacier. Nothing theoretical about that one. These radar measurements agree closely with the red curves indicating an almost perfectly balanced floating glacier. This “balance” breaks down at two important points: (1) Near -20 km the glacier bottom is shallower than the red draft curve and it is here that the glacier sits on land as it is not floating. (2) Near +22 km we see a large red spike. This is the location of the 2012 break-up.

So, the 2012 ice-island that is anchoring the ice arch in southern Nares Strait is the piece of the glacier to the right of the red spike and with these data I can now conclude that PII-2012 was 11 km long, 15 km wide, and about 200 m deep. This Manhattan-sized ice-cube weights about 30 gigatons (10^12 kg), but “… that doesn’t mean much — who goes to the store and buys a gigaton of carrots? For a sense of perspective, a gigaton is about twice the mass of all people on earth …” [James Fallows writing for The Atlantic]. Hence this little ice-cube weights 50 times as much as do all people living on earth today. Incidentally, it is also the amount of CO2 that all humanity adds each year to the atmosphere. Coincidence.

Front of Petermann Glacier Aug.-11, 2012. View is from a small side-glacier towards the south-east across Petermann Fjord with Petermann Gletscher to the left (east). [Photo Credit: Erin Clark, Canadian Coast Guard Ship Henry Larsen]