Tag Archives: Arctic Ocean

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 …

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

Surface Currents, Satellite Imagery, and Software

Technology is advancing at break neck speeds, and with the release of the iPhone 6, US culture seems more obsessed than ever with it.  All one has to do is observe any populated locale to notice the direct impact of the “smart” phone on pedestrians walking down the street or, heaven forbid, people driving cars inches away from said pedestrians.  So, computers dominate our lives (including mine), but as a graduate student of Physical Ocean Science and Engineering I am encouraged to push technological limits. Here is one example that will endanger no pedestrians:

Im_1Veloc_fieldIm_2

Recently, I was directed to a new MATLAB software package that compares pixel movement between two images taken at different times.  I applied this software to satellite imagery of the NE Greenland coastal shelf to identify surface currents from moving ice.  Two of the images above were taken by MODIS on August 18th (Left) and August 19th (Right), 2014.  The images show the surface of the coastal ocean near NE Greenland; white dots are pieces of ice.   The highlighted region in the middle figure shows a velocity field derived from these two days indicating ice motion towards the South.  Listed below is a larger version of the middle figure.

Veloc_field

What does this mean?  Well, based on the work of Falck (2001), this water is on its way from the Arctic Ocean. The surface water is relatively fresh, and as we move from fall to winter this water will cool and new ice will form quickly. Notice that the waters to right in the images are largely clear of ice and that it is this southward current that keeps the ice in a banded structure. This is not something the new iPhone 6 will help me with, but some of the software in the iPhone camera could prove helpful, as I may just have learned in a seminar on bubbles of air bursting from breaking waves.

Falck, E. (2001), Contribution of waters of Atlantic and Pacific origin in the Northeast Water Polynya. Polar Research, 20: 193–200. doi: 10.1111/j.1751-8369.2001.tb00056.x

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.

Of Moorings, Elephants, Norwegians, and Codswallop

The oceans are cruel, unforgiving, and destructive. Microbes, algae, plankton, fish, and whales all evolved slowly to make the seas their home. We men and women of science and technology race to catch-up Continue reading