Tag Archives: ice island

Arctic Ice Cover and Petermann Fjord, Glacier, and Ice Island Video Footage

The National Snow and Ice Data Center announced today, that the Arctic Ice Area Extent has reached an absolute minimum breaking the record minimum of 2007 with still several weeks of potential melting and retreat to go. This has been anticipated for many weeks now with perhaps the most extensive coverage and intelligent discussions over at Neven’s Arctic Sea Ice Blog.

The graph above shows Arctic sea ice extent as of August 26, 2012, along with daily ice extent data for 2007, the previous record low year, and 1980, the record high year. 2012 is shown in blue, 2007 in green, and 1980 in orange. The 1979 to 2000 average is in dark gray. The gray area around this average line shows the two standard deviation range of the data. The 1981 to 2010 average is in sky blue. Sea Ice Index data. [Credit: National Snow and Ice Data Center]

This is as big a deal, because an ice-covered ocean reflects much more sunlight back into space in summer than a black ocean does that absorbs more heat: a positive feedback. This is why people in hot climates wear white, not black clothes, they like to stay cool. Furthermore, this decline has been ongoing for the last 30 years and the climate models that policy makers rely on did not predict this level of ice cover to occur for another 20-30 years. So, the warming climate and the changes it caused are on an accelerated schedule with regard to the Arctic Sea Ice cover. Also, the remaining ice cover is thinner than it used to be, because the multi-year ice keeps leaving the Arctic faster than it can be formed inside the Arctic. Both the Fram Strait to the east of Greenland and Nares Strait to the west of Greenland export this old, hard, and thick ice that ultimately melts further south. The ice that is left in the Arctic Ocean has become both thinner, younger, and softer, making it easier to melt the next summer.

On somewhat related news from the University of Delaware (UDel), we put two videos together that show a tiny, if spectacular example of a different area that has never been ice-free for at least 150 years when people were looking: Petermann Fjord. On August 10/11, 2012 the Captain and crew of the Canadian Coast Ship Henry Larsen gave us unfettered 18 hours access to the newly ice-free waters of this large glacier that discharges about 6% of the Greenland ice sheet. The UDel press release has the video that is also posted at youtube. As a less professionally assembled version is my first introductory iMovie project, e.g.,

New Ocean Observations in Petermann Fjord

A new ice island separated from Petermann Glacier on July 16, 2012 as reported here first. Less than 4 weeks later, the Canadian Coast Guard Ship Henry Larsen reconnoitered the ice island on Aug.-9 when it blocked the northern half of the entrance of the fjord.

Petermann Ice Island 2012 (PII-2012) as seen Aug.-11, 2012 at the entrance of Petermann Fjord. The view is to the north-west. [Photo Credit: Canadian Coast Guard Ship Henry Larsen.]

I was aboard this ship when Captain Wayne Duffett decide to break into the largely ice-free fjord behind the ice-island after consultations with Ice Services Specialist Erin Clarke. The ice observer had just returned from her second helicopter survey in 2 days with pilot Don Dobbin to assess both ice cover and its time rate of change. From the time the ship entered the fjord behind the ice island, hourly flights to a fixed point at the south-western corner of the ice island ensured that its movement would not cut off the ship’s exit. This approach worked and it gave the science crew of 8 aboard about 18 hours to conduct the very first survey of a previously ice-covered ocean:

Petermann Glacier, Fjord, and Ice Island as seen by MODIS at 865 nm on Aug. 07, 2012 overlaid with survey lines of CCGS Henry Larsen on Aug.-9/10/11, 2012 in red.

We were not funded to do enter the fjord, but our main mission to recover an array of ocean moorings with 3-year long data records covering the 2009-12 period about 100 km to the south in Nares Strait has already been accomplished. So, what does a physical oceanographer do when in uncharted and unknown territory? He drops a number of CTDs, that is, measuring conductivity (C), temperature (T), and depth (D, pressure, really) as the instrument (the CTD) is lowered at a constant rate from the surface to the bottom of the ocean at a number of stations. The results from such work next to the present front of Petermann Glacier was a surprise for which we do not yet have a satisfactory explanation: The waters inside the fjord are much warmer at salinities 32.5-34.25 than they are outside the fjord:

Temperature as a function of salinity from 9 stations across Petermann Fjord next to the current seaward edge of Petermann Glacier on Aug.-10, 2012 in red. For comparison I show in blue a station done outside the fjord on Aug.-9, 2012. Note that temperatures increase with increasing salinity which is expected for waters that are a mixture of cold and fresh polar and saltier and warmer Atlantic waters. Density deviations from 1000 kg/m^3 are shown as solid contours along with the freezing temperature that decreases with increasing salinity.

Another way to show the same data is to actually plot the section, that is, the distribution of temperature and salinity in physical space across the fjord as a function of depth:

Section across the seaward edge Petermann Glacier on Aug.-10, 2012 for salinity (left panel) and temperature (right panel). Symbols indicate station locations from which color contours are drawn. Note that the display is cropped to the top 300 meters while real recordings extend to the bottom which exceeds 1000 meters. The view is eastward towards the glacier with north to the left.

Note the doming salinity contours which to classically trained oceanographers suggest a flow out of the page on the right and into the page on left with maximum at about 90 meter depth relative to no flow at, say, 500 meter depth. Another way to view this distinct property distribution is that the flow above 90 meters is clockwise (outflow on left, inflow on right) relative to the more counter-clockwise flow below this depth. This feature, too, comes as a surprise and requires more thought and analyses to explain.

There is much more work to be done to figure out what all this means. I feel like scratching the surface of a large iceberg half-blind. The data from below 300 meter depth, too, contain clues on how some this glacier interacts with the ocean. As for the purpose of this post, I merely wanted to report that the ice island is presently having a hitting or scratching tiny Hans Island. The latter is unlikely to move, but Petermann’s Ice Island will slow on impact, swivel counter-clockwise, bump into Ellesmere, and pretend nothing has happened on its merry way south. This is the latest image I have:

Petermann Ice Island 2012 on Aug.-22, 2012 as seen by MODIS Terra at 21:45 UTC. The tiny red dot marks Hans Island, the location of a weather station in the Kennedy Channel section of Nares Strait. Petermann Fjord is towards the top right out of view.

ADDENDUM Sept.-1, 2012: PII-2010B had a maximum thickness of at least 144 meters as it passed over a mooring that measures ocean currents from the Doppler shift of acoustic backscatter that is shown here for one of four beams:

Time-depth series of acoustic scatter from a bottom-mounted acoustic Doppler current profiler for 24 hours starting Sept-22, 2010 9:30 UTC. Red colors indicate high backscatter from a “hard” surface like ice. The vertical axis depth in meters above the transducers while the horizontal is ensemble number into the record (0.5 hours between ensembles). The 2010 ice island from Petermann Glacier (PII-2010B) passed over the mooring. When PII-2010B was attached to the glacier it was adjacent to the segment that became PII-2012 this year.

Nares Strait 2012: Charting New Waters in Petermann Fjord

By Andreas Muenchow, off Joe Island, Greenland, Aug.-11, 2012

We just left Petermann Fjord, squeezing by a Manhattan-sized ice island blocking much of its entrance. An armada of 100s of ship-sized tabular icebergs were all jockeying for positions behind the big one. Captain Wayne Duffett of the Canadian Coast Guard commanded the CCGS Henry Larsen into the new waters of Petermann Fjord, Greenland, with skill, experience, and a calculated dose of daring, trusting both his instincts and his crew. These new waters were formed when Petermann Glacier lost as much as 1/3 of its floating ice shelf during massive break-off events in 2010 and again in 2012. The Henry Larsen was the first and only ship for years to sail and survey this mare incognita for the last 22 hours. It was a long day.

I slept only one of the last 24 hours, skipped dinner, and will head for breakfast in 10 minutes. Being excited and working hard with 24 hours of daylight is exhausting, draining, but also immensely satisfying. We completed a spatial bathymetric survey, collected water and water properties along the new seaward face of the glacier from the surface to 1200 meter depth, and did the same for a section along the axis of the fjord that used to be covered by an ice-shelf.

I tried to document and capture the changing icy seas and their interactions with both land and ocean by taking plenty of photos and video, to later share with those who cannot be here. Several pods of narwhales — they really do have 3-ft long tusks (a tooth really) — were feeding on ocean fronts within a mile of Petermann Glacier’s new face…

Breakfast is ready; I am sending this off as is, without much editing (too tired) {Editor’s note:  Good thing there are those less distracted by the excitement of new icy worlds to do some proofreading…}, then some sleep while those who sleep will install a new weather station on Joe Island.  Science aboard a ship like the CCGS Henry Larsen never really stops…

Petermann Glacier, Ice Islands, and Changing Climate

Petermann Glacier is a tidewater glacier in the remote north-west of Greenland. The glacier is grounded at about 600-m below sea level. It has calved two large ice islands, a 4-Manhattan sized island in 2010 and a 2-Manhattan sized one in 2012. These losses cover much of the area shown in this 2009 photo:

Eastern wall of Petermann Fjord as seen from CCGS Henry Larsen’s helicopter in August 2009 with the floating ice shelf. Most of the visible ice shelf has been lost during the 2010 and 2012 calving events. [Photo Credit: David Riedel, British Columbia.]

From selected imagery, I created a short movie (0.7 MB) which shows (a) the 2010 calving, (b) the advance of the new front in 2011 and early 2012, and (c) the 2012 calving. The glacier has moved at a rate of about Continue reading

Petermann Ice Islands Stuck in Ice

Several pieces of the Manhattan-sized ice island that broke off Petermann Glacier, Greenland in 2010 arrived, dispersed, and melted off Newfoundland last summer. They provided stunning displays visible to the naked eye from the coast. The Canadian Ice Service just distributed this set of radar images showing 4 pieces that are all grounded and/or stuck in ice. None are moving.

Overview of fragments of Ice Islands that broke off Petermann Glacier, Greenland in 2010 as of June-11, 2012 from RadarSat composites. [Credit: Luc Desjardins, Canadian Ice Service]

In the open ocean ice is moved by winds stressing the ice from above and by ocean currents stressing the ice from below. Typical sea ice varies in thickness from 1-5 meters (3-15 feet) which is much less than the 30-130 meters (90-400 feet) thick ice islands. Winds thus push thick ice islands much less than they do push the thinner sea ice. Thick ice islands are moved by ocean currents, not winds.

This is why oceanographers like myself love these bits of ice islands to bits: they tell us about the ocean below the surface that satellites do not see, but, sadly, all fragments are stuck either to the seafloor in shallow coastal waters or are cemented in place by immobile sea ice that is “land-fast:” Think of it as ice that is glued to land and to each other. This sheet of glued-together ice extends some distance offshore. The distance can be a few yards during a cold winter night in Maine or 100s of miles off Siberia. Offshore islands, rocky outcroppings, or grounded ice islands all anchor land-fast ice by adding local support and thus strength and stability to the immobile land-fast ice.

Too much talk, lets explain this with an image of the largest ice islands, called PII-B1. It is about 4 km wide and 9 km long. I dropped a black dot in its center as it is hard to see where to look in this image. I also show land in grey, open water in blue, and ice in shades of white and yellow:

Land-fast and mobile sea ice off Baffin Island with Petermann Ice Island PII-B1 grounded near the 150 meter isobath (black dot). Thick lines are 100, 200, and 300-m bottom depths. MODIS Terra data at 250-m resolution from June-6, 2012, 15:05 UTC.

There is clearly a 30-km wide band of ice attached to the land with a line of blue water separating it from ice that is mobile and has different signatures. A blue band of ocean has emerged, I speculate, as the result of winds from the south that moved the mobile ice to the north-east (to the right in the image). Neither the land-fast nor the grounded ice island PII-B1 embedded in it moved, so open water appears where there was mobile ice before. This is called a shore lead and I bet there are plenty of seals and whales feasting there now. Note also the arched entrance to Home Bay (bottom left) where loose ice is scattered towards the headland of Henry Kater Peninsula.

As summer is arriving fast in the Arctic, the land-fast ice will disappear, breaking up as the sun and air above and the ocean below weakens the ice by melting. This will expose the thicker ice islands and icebergs to wind-forced storms and waves more violently than it does now. And even those ice island grounded to the bottom of the ocean in shallow water will become free during a time of higher than normal sea level, perhaps during a spring tide, perhaps during strong winds from the north. Then these currently stuck-in-the-ice ice islands will continue their journey south towards Newfoundland and the Atlantic Ocean that they began in 2010 when they were born in northern Greenland.

EDIT: For context I append an earlier RadarSat image from October-18, 2010 when all segments were much closer in space.

Petermann Ice Islands in northern Baffin Bay of Coburg Island, Canada at 76 N latitude on Oct.-18, 2010, about 2 month after they separated from Petermann Glacier, Greenland at 81N latitude. [Credit: Luc Desjardins, Canadian Ice Service]