Tag Archives: climate change

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

Fish, Fashion, and Climate: Simple Thoughts on Complex Systems

I love pickled herring, but the fashion of eating this delicacy varies with changing cultures and climates. In northern Europe it used to be a standard fare, perhaps still is, but in my native coastal North-Germany it was poor man’s food Continue reading