Tag Archives: climate change

The Ice Shelf of Petermann Gletscher and its Ocean Below: Descriptions

“In 1921 owing to starvation I had to go directly from Cape Heiberg-Juergensen to our cache at Cape Agassiz … during this journey the greater part of the glacier was mapped.” –Lauge Koch, 1928

Petermann Fjord connects Petermann Gletscher to Nares Strait which in turn is connected to the Arctic Ocean in north and the Atlantic Ocean in the south (Figure-2). The track of Petermann ice island PII-2010A emphasizes this connection as the 60 meter thick section of the ice island reaches the Labrador Sea in the south within a year after its calving in 2010.


PII-2010 left Petermann Fjord on the 9th of September in 2010 when it broke into segments A and B while pivoting around a real island. It flushed out of Nares Strait 10 days later when an ice-tracking beacon was placed to track the ice island. The ~60 m thick segment PII-2010A moved southward with the Baffin Island Current (Münchow et al., 2015) at an average speed of ~ 0.11 m/s past Davis Strait. Remaining on the continental shelf of the Labrador Sea, it passed Boas’ Cumberland Sound, Labrador, and reached Newfoundland in August 2011 when it melted away in a coastal cove about 3000 km from Petermann Fjord (Figure-2).


Petermann Gletscher drains about 4% of the Greenland ice sheet via a network of channels and streams that extend about 750 km landward from the grounding line (Bamber et al., 2013). The glacier goes afloat at the grounding zone where bedrock, till, and ice meet the ocean waters about 600 meter below sea level (Rignot, 1996).


Figure-3 shows a section of surface elevation from a laser altimeter flown on a repeat path along the glacier in April 2013 and May 2014 as part of NASA’s Operation IceBridge. Assuming hydrostatic balance, we also show basal topography below the sea surface that varies from 200 meters at the terminus to 600 meters at the grounding zone near distance zero (Figure-3). The 2013 profile has been shifted seaward by 1.25 km to match the terminus position. Note the close correspondence of large and small crevasses in 2013 and 2014 near 20, 40, and 45 km from the grounding zone.

The seaward shift of the 2013 relative to the 2014 profile implies a uniform glacier speed of about 1180 meters per year. This value is almost identical to the 1170 meters per year that we measure between 20th August of 2015 and 11th February of 2016 with a single-frequency GPS placed about 13 km seaward of the grounding zone as part of the ocean weather observatory.

We compare 2013/14 and 2015/16 velocity estimates in Figure-3 with those obtained from RadarSat interferometry between 2000 and 2008 (Joughin et al., 2010) of which I here only show three:

Figure-3 shows that glacier speeds before 2010 are stable at about 1050 m/y, but increased by about 11% after the 2010 and 2012 calving events. This increase is similar to the size of seasonal variations of glacier motions. Each summer Petermann Gletscher speeds up, because surface meltwater percolates to the bedrock, increases lubrication, and thus reduces vertical friction (Nick et al., 2012). Figure 3 presents summer velocity estimates for August of 2015 from three dual-frequency GPS. The along-glacier velocity profiles measured by these geodetic sensors in the summer follow the shape of the 2000 to 2008 winter record, however, its speeds are about 10% larger and reach 1250 m/y near the grounding zone (Figure 3).

Uncertainty in velocity of these GPS systems is about 1 m/y which we estimate from two bed rock reference stations 82 km apart. Our ice shelf observations are referenced to one of these two semi-permanent geodetic stations. Its location at Kap Schoubye is shown in Figure-1. Data were processed using the GAMIT/TRACK software distributed by MIT following methodology outlined by King (2004) to archive vertical accuracy of 2-3 centimeters which, we show next, is small relative to tidal displacements that reach 2 meters in the vertical.


Figure-4 shows the entire 13 day long record of vertical glacier displacement from 30 seconds GPS measurements in August of 2015. The observed range of vertical glacier displacements diminishes from almost 2 meters about 26 km seaward of the grounding zone (GZ+26) via 0.6 meters in the grounding zone (GZ-00) to nil 20 km landward of the grounding zone (GZ-20). Anomalies of horizontal displacement are largest at GZ-00 with a range of 0.2 m (not shown) in phase with vertical oscillations (Figure-4).

More specifically, at GZ+26 we find the ice shelf to move up and down almost 2 meters roughly twice each day. This is the dominant semi-diurnal M2 tide which has a period of 12.42 hours. Notice that for each day there is also a diurnal inequality in this oscillation, that is, the two maximal (minimal) elevations oscillate from a higher to a lower High (Low) water. This is the diurnal K1 tide which has a period of 23.93 hours. And finally, all amplitudes appear modulated by some longer period that appears close to the record length of almost two weeks. This is the spring-neap cycle that is caused by a second semi-diurnal S2 tide that has a period of 12.00 hours. A formal harmonic analysis to estimate the amplitude and phases of sinusoidal oscillations at M2, K1, S2 and many more tidal constituents will be published elsewhere for both Petermann Fjord and Nares Strait. Preliminary results (not shown) reveal that the amplitudes and phases of the tidal signals at GZ+26 are identical to those observed off Ellesmere Island at 81.7 N latitude in both the 19th (Greely, 1888) and 21st century.

Hourly tidal observations at Discovery Harbor taken for 15 days by Greely in 1881 and Peary in 1909.

Hourly tidal observations at Discovery Harbor taken for 15 days by Greely in 1881 and Peary in 1909.

In summary, both historical and modern observations reveal real change in the extent of the ice shelf that moves at tidal, seasonal, and interannual time scales in response to both local and remote forcing at these times scales. Future studies will more comprehensively quantify both the time rate of change and its forcing via formal time series analyses.

P.S.: This is the second in a series of four essays that I am currently developing into a peer-reviewed submission to the Oceanography Magazine of the Oceanography Society. The work is funded by NASA and NSF with grants to the University of Delaware.


Bamber, J.L., M.J. Siegert, J.A. Griggs, S. J. Marshall, and G. Spada. 2013. Palefluvial mega-canyon beneath the central Greenland ice sheet. Science 341: 997-999.

Greely, A.W. 1888. Report on the Proceedings of the United States Expedition to Lady Franklin Bay, Grinnell Land. Government Printing Office, Washington, DC.

Joughin, I., B.E. Smith, I.M. Howat, T. Scambos, and T. Moon. 2010. Greenland flow variability from ice-sheet wide velocity mapping. Journal of Glaciology 56 (197): 415-430.

King, B. 2004. Rigorous GPS data-processing strategies for glaciological applications. Journal of Glaciology 50 (171): 601–607.

Münchow, A., K.K. Falkner, and H. Melling. 2015. Baffin Island and West Greenland current systems in northern Baffin Bay. Progress in Oceanography 132: 305-317.

Nick, F.M., A. Luckman, A. Vieli, C.J. Van Der Veen, D. Van As, R.S.W. Van De Wal, F. Pattyn, A.L. Hubbard, and D. Floricioiu. 2012. The response of Petermann Glacier, Greenland, to large calving events, and its future stability in the context of atmospheric and oceanic warming. Journal of Glaciology 58 (208): 229-239.

Rignot, E. 1996. Tidal motion, ice velocity and melt rate of Petermann Gletscher, Greenland, measured from radar interferometry. Journal of Glaciology 42 (142): 476-485.

Taking the Pulse of Petermann Gletscher

Posted by Pat Ryan for Andreas Muenchow

23-August-2015 at 80:57.3 N 061:27.1 W

(note correction below)

I just may have made a discovery that I cannot share with anyone on the ship right now. The giant mass of ice that is Petermann Gletscher just slowed down moving only 1 meter per day for the last 3 days rather than the 3 meters per day that it usually does and that has been reported in the scientific literature. This measurement comes from the newly deployed University of Delaware weather station that also contains a not-so-fancy $300 Garmin GPS as well as 5 ocean sensors that measure temperature and salinity about 95-m, 115-m, 300-m, 400-m, and 810-m below the surface of the floating and moving ice.

Time Series of Glacier Drift

Time Series of Glacier Drift (correction appears below)

As the glacier puts on the breaks, I also see a rather dramatic increase in ocean temperature from -0.6 to -0.35 degrees Celsius within about 10-m of the ice-ocean interface. The saltiness of the ocean also increased from below 34.1 to above 34.2 practical salinity units that you can think of as grams of salt per kilogram of water, roughly. Only 20 m below in the water column, the opposite is happening: The water there cools a little bit and becomes fresher. This suggests some mixing as the salinity differences become smaller and heat from the lower layer moves up towards the ice. Some force must be applied to the fluid to do this. Recall that a force is mass times acceleration. The force of a mosquito splashing on the wind shield of your car is small, because the mass of the mosquito is small even though its acceleration (from zero to the speed of your car) is large. Now imaging this glacier: Its mass is enormous, so you only need to change its velocity a tiny amount, from 3 to 1 meter per day, say, to generate a massive amount of force.

Photo of helicopter deck with Belgrave (left) and Petermann (right) Glaciers in back Aug.-23, 2015; view is to the north-east.

Photo of helicopter deck with Belgrave (left) and Petermann (right) Glaciers in back Aug.-23, 2015; view is to the north-east.

As I look outside my cabin window right now, I see the terminus of Petermann sitting there innocently not appearing to do much, but it is literally changing the face of the earth as it moves fast, slows down, moves some more, and over 1000s of years cut a very deep fjord and perhaps canyon deep into the mountains and even deeper into the sea floor. The helicopters are whizzing overhead right now returning all the gear that was needed to drill through 100s of meters of hard glacier ice to provide access holes to both ocean and sediments that has been in total darkness for many 100s of years.

Photo of helicopter delivering cargo from the finished ice camp back to the ship on 23 Aug. 2015.

Photo of helicopter delivering cargo from the finished ice camp back to the ship on 23 Aug. 2015.

Still, there is life down there, lots of it Anne Jennings, who closely looks at the sediment cores, tells me. We speculate that the life is supported by vigorous ocean flow that connects the open fjord with the glacier covered deep ocean. Food stuff like plankton may move some distance under the floating glacier to support a population of other critters that I know nothing about. No narwhals this year so far, though.

So why I am writing this up here rather than share it with people on the ship? Well, this is Sunday morning and there was much to celebrate last night when the ice drilling team returned after 2 weeks camping on the ice and collecting data from their three drill holes. Furthermore, the the ocean weather station reported for the first time in over 2 days uploading all the data I show above. This happened well past midnight and several of us discussed the data and future plans in the cafeteria until 1:30 am. So the people not working right now are all sleeping (10:30 am here) as we probably will work through the night to map the Atlantic waters flowing into the fjord at its sill towards Nares Strait …  which we have not yet done over the 3 weeks we have been in the area. I probably also should help with unloading the helicopters or getting the Chief Scientist Alan the data files he needs to catalogue the water samples we collected last night. Work on Oden never stops … as there is so much to do as we are barely scratching the surface or bottom of the ocean here. [Incoming helicopter, 4th one since I wrote these lines too fast, perhaps.]

Screenshot of a successful RS-232 serial connection from ship to ocean weather station on Petermann Gletscher and ocean sensors deployed 810 m below the glacier’s ice surface with active real time data transmissions. This session uploaded new codes to the secondary data logger to activates its secondary back-up memory.

Screenshot of a successful RS-232 serial connection from ship to ocean weather station on Petermann Gletscher and ocean sensors deployed 810 m below the glacier’s ice surface with active real time data transmissions. This session uploaded new codes to the secondary data logger to activates its secondary back-up memory.


Petermann Gletscher did slow down the last few days by about 10% as measured by the GPS at the UDel ocean-weather station. The suggested slow-down to 300 meters per year, however, is false, because I did not properly take into account how the station was moved by 30 meters to the south-west. The correct and updated estimate is the figure below. Please discard the the above figure erroneous.

Sorry for the confusion … more data coming from this station will place the short term change in glacier speeds into a larger context. Furthermore, the present “cheap” GPS system will need to be verified by a set of three “fancy” differential UNAVCO GPS that were recovered today, but we have not yet decoded the data contained on those units.

Back to CTD profiling the water properties across the sill at the entrance to Petermann Fjord that we will have to complete by 3 am or in about 6 hours.

Time Series of Glacier Drift (Corrected)

Time Series of Glacier Drift (Corrected)

Heartbeat of Ocean and Air of Greenland

While cables are designed at a small company in southern California,while instruments are shipped to friends at the British Antarctic Survey in England, while instrument locations are contemplated by a small group of scientists, technicians, and graduate students, I am also on a journey back in time to check up on the heart beat of the air we breath and the oceans we sail. The Arctic heartbeat to me is the annual change from the total darkness of polar night to total sunlight of polar day. This cycle, this heartbeat takes a year. There is 24 hours of day in summer the same way that there is 24 hours of night now. Let me first show, however, where we are heading before I look at the heartbeat.

I love making maps and this is a rich and pretty one that shows North America from the top where Petermann Fjord and Glacier are (tiny blue box on left map). The colors are water depths and land elevations. The thick dotted red line is where a very large iceberg from Petermann traveled within a year to reach Newfoundland. Teresa, one of the contributors to my crowd-funding project, sailed up there to Newfoundland to see this iceberg. And she made a movie out this voyage. So, what happens up there in northern Greenland only takes a year, maybe two, to reach our more balmy shores. What happens in Greenland does NOT stay in Greenland. Vegas, Nevada this is not.


Now on to the map on the right. This is the tiny blue box made much larger. It looks like a photo, and in a way it is, but a photo taken by a satellite, well, only one “channel” of this specific satellite, the many shades of gray are mine, it is NOT the real color. The glacier is in the bottom right as the white tongue sticking out towards 81 N latitude. Red lines there are water depths of 500 and 1000m. The blue dot in the top-left is where I had to leave an ocean sensor in a shallow bay for 9 years, because we could not get there to retrieve it for 6 years. Lucky for me (well, some smart design helped), the instrument was still there, collecting and recording data that we knew nothing about for 9 long years. It took smart and hardy fishermen from Newfoundland aboard the CCGS Henry Larsen to dangle my sensor out of the icy waters. And here is the heart beat it revealed:


Top graph is ocean temperature, bottom panel is air temperature nearby. And as you go from left to right, we move forward in time starting in 2002 until the end of 2012 when the last ocean measurements were made. The red lines are a linear trend that represents local (as opposed to global) warming. Both go up which means it gets warmer, but careful, the bottom one for air is no different from a straight line with zero slope meaning no warming. It does go up, you say correctly, but if I do formal statistics, this slope is no different from zero just due to chance. The top curve for the ocean, however, is very different. It does not look different, but the same statistics tell me that the warming is NOT due to chance alone. Oh, in case you wondered, the two dashed lines in the top panel are the temperatures at which seawater freezes and forms ice for the salinity range we see and expect at this embayment. As you add salt to water, it freezes at a lower temperature. This is why we put salt on our roads in winter, it makes the water freeze less fast.

I am a doctor, so here is my conclusion: Ocean heart beat is a little irregular and the trend is not good news for the ice. Air heart beat looks normal, the trends may need watching, but I am not too worried about that just yet. Watch the oceans … that’s where the heat and the action is these days.

Jon Steward on Climate Change

I missed this episode when it aired last year, but it is one of the very best Daily Shows and it is on Climate Change to boot (3 minutes into the video the good stuff starts):

Partial credit to Nick Clark who included it a rich and wonderful Al Jazeera essay entitled Global doom and gloom? Here’s some sunshine.

Arctic Heart Beat and Disappearing Old Ice

Have a look at this beautiful movie that shows how the Arctic Ocean moves its oldest and thickest ice around from 1987 through 2013: Continue reading