Author Archives: Andreas Muenchow

Changing Weather, Climate, and Drifting Arctic Ocean Sensors

Three people died in Buffalo, New York yesterday shoveling snow that arrived from the Arctic north. The snow was caused by a southward swing of air from the polar vortex that is all wobbly with large meanders extending far south over eastern North-America where I live. Physics deep below the thinly ice-covered Arctic Ocean hold a key on why we experience the Arctic cold from 2000 km north and not the Atlantic warmth from 100 km east.

A wobbly jet stream that separates cold Arctic air from warmer mid-latitude air. Note the strong gradients over eastern North America. [From wxmaps.org]

A wobbly jet stream on Nov.-19, 2014 that separates cold Arctic air from warmer mid-latitude air. Note the strong differences over eastern North America and how balmy Europe, Russia, and Alaska are. [From wxmaps.org]

The Arctic Ocean holds so much heat that it can melt all the ice within days. The heat arrives from the Atlantic Ocean that moves warm water along northern Norway and western Spitsbergen where the ocean is ice-free despite freezing air temperatures even during the months of total darkness during the polar night. As this heat moves counter-clockwise around the Arctic Ocean to the north of Siberia and Alaska, it subducts, that is, it is covered by cold water that floats above the warm Atlantic water.

North-Atlantic Drift Current turning into the Norwegian Current that brigs warm Atlantic waters into the Arctic Ocean to the north of Norway and Spitsbergen. [Credits: Ruther Curry of WHOI and Cecilie Mauritzen of Norwegian] Meteorological Institute]

North-Atlantic Drift Current turning into the Norwegian Current that brigs warm Atlantic waters into the Arctic Ocean to the north of Norway and Spitsbergen. [Credits: Ruther Curry of WHOI and Cecilie Mauritzen of Norwegian] Meteorological Institute]

But wait a minute, how can this be? We all learn in school that warm air rises because it is less dense. We all know that oil floats on water, because it is less dense. Well, the warm Atlantic water is also salty, very salty, while the colder waters that cover it up are fresher, because many larger Siberian rivers enter the Arctic Ocean, ice melted the previous summer, and fresher Pacific waters enter also via Bering Strait. So, the saltier and more dense Atlantic water sinks below the surface and a colder fresher layer of water above it acts as a insolation blanket that limits the amount of ocean heat in contact with the ice above. Without this blanket, there would be no ice in the Arctic Ocean and the climate everywhere on earth would change because the ocean circulation would change also in an ice-free Arctic Ocean, but this is unlikely to happen anytime soon.

A single profile of temperature and salinity from an ice-tethered profile (ITP-74) off Siberia in July 2014. Note the warm Atlantic water below 150 meter depth.

A single profile of temperature and salinity from an ice-tethered profile (ITP-74) off Siberia in July 2014. Note the warm Atlantic water below 150 meter depth.

Some wonderful and new science and engineering gives us a new instant perspective on how temperature and salinity change over the top 700 meters of the Arctic Ocean every 6 hours. Scientists and engineers at the Woods Hole Oceanographic Institution with much support from American tax-payers keep up many buoys that float with the ice, measure the oceans below, and send data back via satellites overhead to be posted for all to see on the internet. Over the last 10 years these buoys provide in stunning detail how the Arctic Ocean has changed at some locations and has been the same at other locations. I used these data in an experimental class for both undergraduate and graduate students to supplement often dry lecture material with more lively and noisy workshops where both I and the students learn in new ways as the data are new … every day.

For well over 50 years the Soviet Union maintained stations on drifting Arctic sea ice that stopped when its empire fell apart in 1991. Russia restarted this program in 2003, but unlike the US-funded automated buoys, the Russian-funded manned stations do not share their data openly. No climate change here …

Shellshock Bugs, Macs, and Unix Powers

I love my Apple to bits. My writing, teaching, coding, graphing, and playing are all done on a MacBookPro with two Intel 2.4 GHz processors running OS X 10.5.8 called “Leopard.” It was the up-to-date operating system from 2006-2009 and I never saw the need to change, as I was too lazy to fix something that is not broken. Until today when I learnt of a vulnerability deep inside the guts of my beloved Unix-machines.

For over 5 years this laptop has been running non-stop doing scientific computing on huge amounts of ice, ocean, and satellite data. It is this Unix environment that I cherish as it is open, transparent, elegant, and concise. It also allows me to use unlimited codes and tools of many open-source communities. My Apple also traveled with me on ships and planes to Arctic Canada, Greenland, Norway, Germany, and anywhere in-between. It travels daily on my bicycle from home to work and back.

Today I was worried when my student Pat told me about shellshock, a bug that potentially can give control to a hostile party smart enough to exploit this vulnerability for which Apple has not yet released a patch. So, did I have a problem? You bet.

STEP-0: From a terminal I entered the command

env x=’( ) { : ; }; echo vulnerable’ bash -c “echo this is a test”

If the word “vulnerable” appears, then the bug is present. Also check the second flavor of the bug by entering the command

env X=’( ){(a) =>;\’ bash -c “echo date”; cat echo; rm -f echo

If you see the actual date displayed (as opposed to the word “date”), then again you got the buggy code. Here is how I fixed it on my laptop and MacMini that hosts my work web-pages.

Step-1: I took this technical recipe, but not all elements worked for me:

$ mkdir bash-fix
$ cd bash-fix
$ curl https://opensource.apple.com/tarballs/bash/bash-92.tar.gz | tar zxf -

The above line failed me, but the added option -k worked to download the needed files from apple.com with the curl-command; the same was also true for the two other curl commands below that downloaded the patches from gnu.org It applies the patches to the files uploaded from apple.com prior.

$ curl -k https://opensource.apple.com/tarballs/bash/bash-92.tar.gz | tar zxf -
$ cd bash-92/bash-3.2
$ curl -k https://ftp.gnu.org/pub/gnu/bash/bash-3.2-patches/bash32-052 | patch -p0
$ curl -k https://ftp.gnu.org/pub/gnu/bash/bash-3.2-patches/bash32-053 | patch -p0
$ cd ..
$ sudo xcodebuild

STEP-2: The above line “sudo xcodebuild” did not work for me for reasons I do not understand. I realized, however, that it was supposed to compile the patched codes to produce executable new files “bash” and “sh” free of the bug. I searched for and found the code-building application XCode.app on my computer as /Developer/Application/XCode.app and started it by point and click. Then via File > Open File I found the relevant “project file” bash.xcodeproj that was in the directory created previously, that is, bash-fix/bash-92 which I then opened within XCode.app Hit the button with the hammer called “Build and Go” and you build yourself a new bash.

Screenshot of compiling patched bash.xcodeprof using XCode.app

Screenshot of compiling patched bash.xcodeprof using XCode.app

STEP-3: Once the compilation and building of the executables is complete, all that needed to be done was to move the newly created, patched executable shells “bash” and “sh” into their rightful places deep within the guts of the operating systems. First, however, lets just save the buggy old files. From the command line

$ sudo cp /bin/bash /bin/bash.old
$ sudo cp /bin/sh /bin/sh.old

and as the last step move the new, patched “bash” and “sh” to their
root directory /bin:

$ sudo cp build/Release/bash /bin/.
$ sudo cp build/Release/sh /bin/.

I moved the binary files “bash” and “sh” to my web-hosting MacMini after renaming the old buggy ones, oh, and as a good practice (short
of deleting those old system files), I changed the permission settings.

Credit for this way to reduce a vulnerability on my dear machine belongs to this concise blog whose content is also presented in a more chatty voice. Wired Magazine adds a little drama in their story titled “The Internet Braces for the Crazy Shellshock Worm, but it took me longer to write and assemble this essay than it did patching the bug.

Unix is fun to hack.
Eric S. Raymond

Unix is not so much an operating system as an oral history.
— Neal Stephenson

ADDENDUM Sept.-28, 2014: A quick online to test for vulnerable web-sites and cgi scripts.

A Short Summary of Nares Strait Physics

The Arctic Ocean is a puddle of water covered by ice that melts, moves, and freezes. Grand and majestic rivers of Siberia and America discharge into the puddle and make it fresher than Atlantic Ocean waters. The fate of the Arctic freshwater helps decide if Europe and the US become warmer or colder, experience more or less storms, droughts, or floods, and if global sea level will rise or fall. In a nutshell: the fate of Arctic freshwater determines climate.

Arctic Ocean with Nares Strait study area (red box) with tide gauge locations as blue symbols and section of moored array as red symbol. Contours are bottom topography that emphasize ocean basins and continental shelf areas.

Arctic Ocean with Nares Strait study area (red box) with tide gauge locations as blue symbols and section of moored array as red symbol. Contours are bottom topography that emphasize ocean basins and continental shelf areas.

Nares Strait connects the Arctic and Atlantic Oceans to the west of Greenland. It is narrower than Fram Strait, but it transports as much fresh ocean water as does its wider sister facing Europe. Few people know this, including climate scientists who often model it with a bathymetry that is 10,000 years out of date from a time when Nares Strait did not yet exist. This is why the US National Science Foundation funded a group of oceanographers to use icebreakers, sensors, computers, and innovative engineering to collect and analyze data on the ice, the water, and the atmosphere.

Acoustic Doppler Current Profiler mooring deployment in Nares Strait from aboard the CCGS Henry Larsen in 2009.

Acoustic Doppler Current Profiler mooring deployment in Nares Strait from aboard the CCGS Henry Larsen in 2009.

Within days of the start of the grant I had to appear before the US Congress to answer questions on Petermann Glacier that discharges into Nares Strait. In 2010 a large 4-times Manhattan-sized ice islands broke off and people wanted to know if global warming was to blame. I was asked how ocean temperatures and currents relate to this and other events and what may happen next. My few data points were the only existing data for this remote region, but I had not yet had the time to analyze and publish much. Two years later another large 2-Manhattan sized ice island formed from the same glacier, but this time we were better prepared and people world-wide went directly to our data, thoughts, and stories when this blog was sourced in news papers in France, Germany, and China. Al Jezeraa, BBC, and PBS reported on it, too, giving me chance to connect via TV, radio, and pod-casting to a larger public.

Petermann Gletscher in 2003, 2010, and 2012 from MODIS Terra in rotated co-ordinate system with repeat NASA aircraft overflight tracks flown in 2002, 2003, 2007, and 2010. Thick black line across the glacier near y = -20 km is the grounding line location from Rignot and Steffen (2008).

Petermann Gletscher in 2003, 2010, and 2012 from MODIS Terra in rotated co-ordinate system with repeat NASA aircraft overflight tracks flown in 2002, 2003, 2007, and 2010. Thick black line across the glacier near y = -20 km is the grounding line location from Rignot and Steffen (2008).

While it was exciting and fun to share Nares Strait and Petermann Gletscher physics with a global audience, it is not what we had planned to do. Our goal was to put real numbers to how much water, ice, and freshwater was moving from the Arctic to the Atlantic via Nares Strait. So the next 3 years we labored through our extensive records to first describe and then to understand what was happening in Nares Strait. We found that ocean currents move water always to the south no matter if ice covers Nares Strait or not, no matter if the ice is moving or not, no matter which way the wind is blowing. The physical cause for this southward flow is that the sea level is always a few inches higher in the Arctic Ocean than it is in Baffin Bay and the Atlantic Ocean to the south.

Linear regression of volume flux  through Nares Strait from current meters with along-strait sea level difference from tide gauges (unpublished).

Linear regression of volume flux through Nares Strait from current meters with along-strait sea level difference from tide gauges. (unpublished).

We know, because we measured this with tide gauges that we placed in protected coastal bays. We recovered 3 sensors; most rewarding was the recovery of one sensor that we had failed to reach in 2005, 2006, 2007, and 2009, but in 2012 we finally got the instrument and 9-years of very good data. Batteries and computers inside were still running and recording. I have never seen as clean and as long a time series.

Results from a 2003-12 tide record shows as power spectra with named tidal constituents at diurnal (~24 hours) and semi-diurnal (~12 hours) periods. The red line is a modeled red noise spectra (unpublished).

Results from a 2003-12 tide record shown as a power spectra with named tidal constituents at diurnal (~24 hours) and semi-diurnal (~12 hours) periods. Data are shown as the relative amplitudes of oscillations at frequencies in cycles per day or cpd. The red line is a modeled red noise spectra (unpublished).

From satellite data that we analyzed as part of this grant, we know when the ice moves and when it stops moving. The freeze-up of Nares Strait comes in one of three forms: 1. Ice stops moving in winter, because an ice barrier (ice arch or ice bridge) forms in the south that blocks all southward motion of ice; 2. only new and young ice moves southward, because an ice barrier forms in the north that blocks all entry of Arctic ice into Nares Strait; and 3. Arctic ice moves freely through Nares Strait, because no ice barriers are present. Our 2003-12 study period covers years for each of these different ice regimes. And each of these regimes leads to very different ocean (and ice) flux as a result of very different ocean physics.

Data alone cannot make definite statements on what will happen next with our climate, but we know much new physics. The physics suggest certain balances of forces and energy for which we have mathematical equations, but these equations must be solved on computers that can only approximate the true physics and mathematics. These computer models are our only way to make predictions ito the future. The data we here collected and our analyses provide useful checks on existing models and will guide improved models.

June-10, 2012 MODIS-Terra image showing location of moored array that was deployed in Aug. 2009 to be recovered in Aug. 2012.

June-10, 2012 MODIS-Terra image showing location of moored array that was deployed in Aug. 2009.

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

Münchow, A., Falkner, K., Melling, H., Rabe, B., & Johnson, H. (2011). Ocean Warming of Nares Strait Bottom Waters off Northwest Greenland, 2003–2009 Oceanography, 24 (3), 114-123 DOI: 10.5670/oceanog.2011.62

Münchow, A., Padman, L., & Fricker, H. (2014). Interannual changes of the floating ice shelf of Petermann Gletscher, North Greenland, from 2000 to 2012 Journal of Glaciology, 60 (221), 489-499 DOI: 10.3189/2014JoG13J135

Münchow, A., Falkner, K., & Melling, H. (2014). Baffin Island and West Greenland Current Systems in northern Baffin Bay Progress in Oceanography DOI: 10.1016/j.pocean.2014.04.001

Rabe, B., Johnson, H., Münchow, A., & Melling, H. (2012). Geostrophic ocean currents and freshwater fluxes across the Canadian polar shelf via Nares Strait Journal of Marine Research, 70 (4), 603-640 DOI: 10.1357/002224012805262725

East Greenland Current Instabilities

The coast off north-east Greenland is a grey, cloudy, and icy place. I spent 4 weeks on a ship earlier this summer to place sensors on the ocean floor to measure water currents, salinity, and temperature. The data shall uncover the mystery of how ocean heat 300 m below the surface gets to glaciers to melt them from below year round. My contribution is a small part of a larger effort by German, Norwegian, Danish, American, and British scientists to reveal how oceans change glaciers and how oceans impact Greenland’s ice sheet, climate, and weather.

So, for months now I am watching rather closely how this ocean looks from space. Usually it is cloudy with little exciting to see, but for 4 days this week the clouds broke and displayed a violently turbulent ocean worthy of a Van Gogh painting:

Satellite image ocean current instabilities on Aug.-19, 2014 as traced by ice along the shelf break, red lines show 500, 750, and 1000 meter water depth. Small blue triangles top left are ocean moorings.

Satellite image of ocean current instabilities on Aug.-19, 2014 as traced by ice along the the shelf break, red lines show 500, 750, and 1000 meter water depth. Small blue triangles top left are ocean moorings.

A wavy band of white near the red lines indicates the East Greenland Current. The red lines show where the water is 500, 750, and 1000 m deep. All waters to the left (west) of the red lines are shallow continental shelf while all waters to the right (east) are deep basin. Some islands and headlands of Greenland appear on the left of the image as solid grey. The image covers a distance about the same as from Boston to Washington, DC or London to Aberdeen, Scotland. Black areas are ocean that is clear of ice while the many shades of white and gray are millions of ice floes that act as particles moved about by the surface flow. Using a different satellite with much higher resolution shows these particles. The detail is from a tiny area to the north-west of the red circle near 77.5 North latitude:

Individual ice particles as seen on the north-east Greenland shelf from LandSat 15-m resolution from Aug.-21, 2014 near 77.5N and 10 W.

Individual ice particles as seen on the north-east Greenland shelf from LandSat 15-m resolution from Aug.-21, 2014 near 77.5N and 10 W.

Strongly white areas indicate convergent ocean surface currents that concentrate the loose ice while divergent ocean currents spread the ice particles out in filaments and swirls and eddies.

This is how many real fluids look like if one takes a snapshot as satellites do. Stringing such snapshots together, I show the fluid motion as comes to life for about 3 days:

Output

Notice how the large crests seaward of the red line between 74 and 75 North latitude grow and appear to break backward. This is an instability of the underlying East Greenland Current. It starts out as a small horizontal “wave,” but unlike the waves we watch at the beach, the amplitude of this “wave” is horizontal (east-west) and not vertical (up-down). The mathematics are identical, however, and this is the reason that I call this a wave. As the wave grows, it become steeper, and as it becomes too steep, it breaks and as it breaks, it forms eddies. These eddies then persist in the ocean for many weeks or months as rotating, swirling features that carry the Arctic waters of the East Greenland Current far afield towards the east. The East Greenland Current, however, continues southward towards the southern tip of Greenland. The wave and eddy processes observed here, however, weaken the current as some of its energy is carried away with the eddies.

I could not find any imagery like this in the scientific literature for this region, but similar features have been observed in similar ocean current systems that transport icy cold waters along a shelf break. The Labrador Current off eastern Canada shows similar instabilities as does the East Kamchatka Current off Russia in its Pacific Far East. And that’s the beauty of physics … they organize nature for us in ways that are both simple and elegant, yet all this beauty and elegance gives us complex patterns that are impossible to predict in detail.

Beszczynska-Möller, A., Woodgate, R., Lee, C., Melling, H., & Karcher, M. (2011). A Synthesis of Exchanges Through the Main Oceanic Gateways to the Arctic Ocean Oceanography, 24 (3), 82-99 DOI: 10.5670/oceanog.2011.59

LeBlond, P. (1982). Satellite observations of labrador current undulations Atmosphere-Ocean, 20 (2), 129-142 DOI: 10.1080/07055900.1982.9649135

Solomon, H., & Ahlnäs, K. (1978). Eddies in the Kamchatka Current Deep Sea Research, 25 (4), 403-410 DOI: 10.1016/0146-6291(78)90566-0

American Adventures Abroad: The Four Germanies

I am American and damn proud of it. I was born in Germany, left almost 30 years ago, and, like a plant from another ecosystem, I am exposed to the new Germany for the first time. I know the difficult histories of both West and East Germany that since 1989 are one united country. The 100 people aboard the research icebreaker R/V Polarstern perhaps represent this new country well. Most crew and scientists were born and raised in either East or West Germany, extinct countries which each had a range of characters to form a distinct and diverse German fabric:

The first person I met when boarding the ship in dry dock was X. After introducing myself as an American scientist to sail the FS Polarstern in stilted if decent German, he revealed to me that he volunteered in the NVA, the soviet-style Nationale Volks-Armee for more than 10 years. Like many low-level Nazis a generation or two before him, he argues that not all was bad in the regime that he served. While this may be true, it strikes me odd, that this is the first things one reveals of oneself and a regime that created walls and killing zones to prevent its own citizens from leaving. Suspecting an uneasy history of guilt, I did not argue despite strong feelings to present different perspectives. Hence his next move is to state that American activities in Europe, Asia, South-America, Middle East, and Africa are the root source of all the problems in these regions. Again, not taking the bait, I listen, ask gentle probing questions to expose more detail, however, not much follows after the first rant that, perhaps, reflects a general feeling more than fact. I heart variations of this theme often in Germany both at sea and on land.

Our nurse and stewardess Kerstin also hails from the former East-Germany where she grew up the same time that I did in West-Germany, but unlike X., she embraces life as it presents itself without resentment, regret, or judgment. She signed on for a year working aboard Polarstern for a sense of adventure and to see the world in a different way. She is naturally curious on all things that relate to people, science, and life. She has little interest in politics, ideologies, and theories on how the world works, but she uses her own mind, experiences, and stories to make everyone around her laugh often. People like her should run the world.

The second Mate, Felix, was in charge when I boarded the ship. He is probably in his early 30ies and gave me the first tour of the ship in dry dock, a task that revealed a deep pride in the ship, its capabilities, and all it represents in a forward-looking modern Germany. He has clearly sailed to many ports and dealt successfully with people of different countries, cultures, and educations. Despite cursing and cussing of an ol’ salt, he is a hard-working, no-nonsense guy who gets things done efficiently. He also smokes like a chimney and likes to drive the ship while breaking sea ice. He did this often and smartly throughout the expedition.

A wonderful surprise to me aboard this ship is the large number of foreigners. There are three Danes aboard one of whom hails from New Zealand; two Canadians, two Belgians, and two Englishmen are aboard; while Brazil, China, Netherlands, Poland and the USA are each represented by one scientist. The two Canadians may as well come from two different countries, as one hails from English-speaking British Columbia and the other from French-speaking Montreal. Catherine’s Quebecoise language and perspectives are the most beautiful of all on this diverse ship. I could listen to her for hours …

Then there is a fourth group aboard who are perhaps the largest: They are the very young Germans who were born after the collapse of the communist empires in the East and they will become the new Germany. It is a foreign country to me, one I like from the distance, and it is a very young country with much potential to make a positive impact in the world.

Science party aboard R/V Polarstern after 4 weeks at sea in July 2014.

Science party aboard R/V Polarstern after 4 weeks at sea in July 2014.