Tag Archives: climate change

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.

Correction:

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.

Figure1

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:

AlertDiscTemp

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

Petermann Gletscher Thawing and Thinning

Greenland’s tidewater glaciers are losing mass, through thinning and retreat, at an increasing rate. Greenland’s glaciers located north of 78 North latitude often end in ice shelves, floating extensions of the glaciers extending up to several tens of km into the adjacent fjords. While most ice shelves of North Greenland have been relatively stable, Petermann Gletscher lost more than 40% of its ice shelf area (36 giga tons) during two major calving events in 2010 and 2012. What remains of Greenland’s ice shelves is threatened by a changing climate, because both regional air and ocean temperatures continue to increase while Arctic sea ice cover continues to decline.

Petermann Gletscher through calving events. White lines show ICESat tracks; red (ambient ice shelf) and blue (central channel) show repeat-track airborne surveys.

Petermann Gletscher through calving events. White lines show ICESat tracks; blue (ambient ice shelf) and red (central channel) show repeat-track airborne surveys.

Using lasers and ice sounding radars aboard NASA planes (Operation IceBridge) as well as lasers on a now defunct satellite (ICESat), oceanographer Laurie Padman, glaciologist Helen A. Fricker, and I just passed peer-review with a study that estimates how much Petermann Gletscher has shrunk and melted over the last decade or so. The quick answer is about 5 meters per year:

(top) Change in ice thickness from 2007 to 2010 from repeat airborne missions. (middle) along-track mean thickness. (bottom) steady-state melt.

(top) Change in ice thickness from 2007 to 2010 from repeat airborne missions. (middle) along-track mean thickness. (bottom) steady-state melt.

In our study we distinguished between 1. a thinning of the floating ice shelf that moves along the glacier as new ice moves from the Greenland ice sheet on land out into the ocean and 2. a non-steady thinning at fixed locations as time passes. The situation is somewhat similar to the flow through a pipe (or river, if you wish) with a constriction. If the same amount of water entering the pipe comes out at the other end, then the flow has to speed up where the pipe becomes narrow. A floating glacier is not quite like water flowing through a pipe, because the ocean underneath and the air above can melt ice making the floating ice shelf thinner as it flows along. If the ice thickness changes along the floating glacier, then melting must take place for a glacier moving seaward at a constant rate. The ice thickness changes along the glacier, but stays constant at a fixed location. This is the steady-state melt.

The non-steady state thinning is the change in ice thickness at a fixed point observed at different times. We estimated this from observations taken along exactly the same tracks that the NASA aircraft flew in 2007 and 2010 before the break-up of Petermann Gletscher. Prior studies could not measure this, because the tracks were not the same or because the signal processing was not up to the task. We find that both the steady and the non-steady contribution is about 5 m per year each. These rates do not vary much between a thin central channel or a thick ambient ice shelf. This came as a little bit of a surprise, because the central channel is often also refered to as a “melt channel,” but it actually melts no different from any other section of the ice shelf. So, the question remains as to what causes the central and many other channels to be there in the first place. The place to look, I feel, is the area where the bed rock, the glacier ice, and the Arctic Ocean meet in what is called the grounding zone. It is here that the gigantic forces of water and ice pulverize rock while a mixture of rock and pressurized water is sand-blasting the ice. Talking about a rock and a hard place …

Our study will appear later this year in the Journal of Glaciology, but pre-prints can be downloaded here. The U.S. tax-paying public funded this study via grants that we received from NASA and NSF. They also funded substantial efforts to make sure, that all data reside in the public domain accessible to anyone anywhere.

Münchow, A., Padman, L., and Fricker, H.A. (2014). Interannual changes of the floating ice shelf of Petermann Gletscher, North Greenland from 2000 to 2012, Journal of Glaciology, in press

Johnson, H., Münchow, A., Falkner, K., & Melling, H. (2011). Ocean circulation and properties in Petermann Fjord, Greenland Journal of Geophysical Research, 116 (C1) DOI: 10.1029/2010JC006519

Rignot, E., & Steffen, K. (2008). Channelized bottom melting and stability of floating ice shelves Geophysical Research Letters, 35 (2) DOI: 10.1029/2007GL031765