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South Pacific Bio-optics Cruise 2014: An Appreciation for Satellite True Color Imagery

April 18th, 2014 by Aimee Neeley

We have spent the last few weeks discussing the differences between inherent and apparent optical properties in the ocean and how we measure them.  Now let’s take a moment to appreciate the information these data give us.  I am sure many of you have seen satellite images of the ocean, hurricanes, etc. on the news and at other outlets.  A lot of work goes into each and every one of those images and they can show remarkable things on a global scale that would be difficult to detect through fieldwork alone.

Below you will see a true color image of a phytoplankton bloom in the Barents Sea that was acquired on August 24, 2012 by  NASA’s MODIS Aqua satellite . The Barents Sea is part of the Arctic Ocean and is located off the northern coasts of Norway and Russia. The word phytoplankton is Latin for plant (phyto) and to wander or drift (plankton).  Phytoplankton can photosynthesize and produce energy from sunlight just like plants do on land.  They also take up carbon dioxide and release oxygen like land plants.  Phytoplankton are an important component of the food chain as other organisms such as zooplankton and fish use them as a food source.  Additionally, they play an important role in the global carbon budget because they can use the carbon (CO2) that is absorbed by the ocean to make sugars.

Barents Sea  phytoplankton Bloom

Barents Sea phytoplankton Bloom

There are many types of phytoplankton that bloom in the ocean including diatoms, dinoflagellates, and coccolithophores, just to name a few.   You can learn more about different phytoplankton groups here.  They all rely on specific nutrients, such as nitrogen (NO3, NO2, etc.), phosphorous (PO4, etc.) and trace metals (iron, magnesium, etc.).  Phytoplankton blooms occur when many individuals, or cells, of one species are present in one region of a body of water (lake, estuary, open ocean), altering the color of the water.  In the image above, the water is dominated by a species of coccolithophore. Coccolithophores are a type of phytoplankton that are covered with plates made of calcite called coccoliths. Calcite, or calcium carbonate, is white giving that creamy white look to the water.  You can learn more about this coccolithophore bloom here.

This next image was recently featured on NASA’s OceanColor website. It was taken off the western coast of Africa where a current called the Benguela current flows northward bringing water from the South Atlantic and Indian Ocean.  In this image from April 10, 2014 we can see a yellow discoloration in the water.  I just learned that this area is prone to toxic hydrogen sulfide precipitation events that have been known to cause fish and other marine animal mortalities.  Amazingly, these events have been captured using satellite imagery.  However, the cause of this particular discoloration has not, as of this post, been determined.  This is where fieldwork comes in!  Still, it is very cool!  Thanks to Norman Kuring at NASA Goddard for locating this feature.

Discoloration in the Benguela Current off the coast of Namibia

Discoloration in the Benguela Current off the coast of Namibia

 

You can enjoy many other satellite images at NASA’s Visible Earth website.

 

References:

http://www.worldatlas.com/aatlas/infopage/barentssea.htm

http://aqua.nasa.gov/

http://earthobservatory.nasa.gov/Features/Phytoplankton/

http://www.bigelow.org/foodweb/microbe0.html

http://protozoa.uga.edu/portal/coccolithophores.html

http://oceancolor.gsfc.nasa.gov/

http://oceancurrents.rsmas.miami.edu/atlantic/benguela.html

http://visibleearth.nasa.gov/

http://oceancolor.gsfc.nasa.gov/cgi/image_archive.cgi?i=423

http://www.sciencedirect.com/science/article/pii/S0967063703001754

 

 

Greenland Aquifer Expedition: On The Ice Sheet!

April 18th, 2014 by Maria-Jose Viñas

By Rick Forster

Our team finally made it to the ice sheet on April 8, after being delayed for almost two weeks due a series of storms. That day, we awoke to patches of blue sky over the village of Tasiilaq and were eager to get to the heliport for our scheduled 11:40 AM flight to the ice sheet. Lingering clouds over the ice sheet delayed our departure about three hours.

The village of Tasiilaq on the day of our flight to the ice sheet in SE Greenland where the Air Greenland B-212 helicopter is based.  (Credit: Rick Foster.)

The village of Tasiilaq on the day of our flight to the ice sheet in SE Greenland where the Air Greenland B-212 helicopter is based. (Credit: Rick Forster.)

Once we saw the Air Greenland helicopter returning from its last trip to the local settlements for the day, we knew our flight was next. The trip to our research site on the ice sheet takes about 30 minutes.

The Air Greenland B-212 helicopter landing in Tasiilaq. (credit: Rick Forster.)

The Air Greenland B-212 helicopter landing in Tasiilaq. (credit: Rick Forster.)

The two-week weather delay meant I had to return to the University of Utah while Clem and Ludo would stay on the ice sheet for about 10 days to gather data and perform experiments on the Greenland aquifer. It was a hard decision to make, but I had commitments and if I stayed with the team on the ice sheet, we would all have to leave before all the science could be completed. Ludo and Clem’s schedules were more flexible so they will be able to extend their trip to spend extra time on the ice. I went with the team to the ice sheet to help unload the camp gear from the helicopter at the research site.

From left to right: Clément Miège, Ludovic Brucker, and Rick Forster happy to be finally boarding the helicopter for the flight to the ice sheet. (Credit: Rick Forster.)

From left to right: Clément Miège, Ludovic Brucker, and Rick Forster happy to be finally boarding the helicopter for the flight to the ice sheet. (Credit: Rick Forster.)

The flight to the site was spectacular, going over sea ice chocked fjords and outlet glaciers draining the ice sheet.

An outlet glacier draining the Greenland ice sheet into an ice covered fjord. The individual rough blocks of ice within the smooth surface of the frozen fjord are icebergs that calved off the glacier last summer and are now trapped in the winter fjord ice. (Credit: Rick Forster.)

An outlet glacier draining the Greenland ice sheet into an ice covered fjord. The individual rough blocks of ice within the smooth surface of the frozen fjord are icebergs that calved off the glacier last summer and are now trapped in the winter fjord ice. (Credit: Rick Forster.)

Once at the research site, our team, including the pilot and flight engineer, quickly unloaded the cargo from the helicopter. The heaviest gear could be left closer to the helicopter, while the lighter pieces needed to be dragged farther away and held down by Ludo and Clem to keep them from being blown away from the winds generated by the helicopter taking off. The ice sheet surface was smooth and soft with knee-deep powder, great for skiing but not so good for moving cargo and setting up camp.

Clem, Ludo, and the science and camp cargo waiting for the helicopter to take off. (Credit: Rick Forster.)

Clem, Ludo, and the science and camp cargo waiting for the helicopter to take off. (Credit: Rick Forster.)

Clem and Ludo will spend the next week and half gathering additional data on the Greenland aquifer from a variety of ice penetrating radar systems and installing an automated weather station for our colleagues at Institute for Marine and Atmospheric research Utrecht.

South Pacific Bio-optics Cruise 2014: Sampling the Global Ocean and a Note on Ocean Acidification

April 15th, 2014 by Aimee Neeley

One of the greatest tools used by oceanographers today for measuring ocean processes is the CTD.  CTD stands for Conductivity, Temperature and Depth.  Conductivity is a measure of ocean salinity.  The CTD is used to collect profile data in the ocean.  The CTD is typically accompanied by a carousel, or rosette, of large bottles (Niskins) that can hold about 10 liters (2.6 U.S. gallons) of water.  Some Niskins are large enough to hold 30 liters.  These bottles have spring-loaded caps that can be triggered to close at specified depths.  The CTD and other sensors, such as a chlorophyll fluorometer, and an Acoustic Doppler Current Profiler (ADCP) that measures current velocities, and other sensors can also be attached within the rosette package.

The whole package is connected to a very long cable and is mechanically lowered by a winch operator down through the water column, which is called the ‘downcast.’ During the downcast, information about salinity, temperature, depth and data from the other sensors are sent to a computer on board the ship.  The computer is connected through the cable that is lowering the package.  The downcast is halted once the package reaches close to the ocean floor.  When the CTD is raised back to the surface, the ‘upcast’, each of the Niskin bottles is closed at assigned depths, collecting water as it travels back to the surface.

Once the Rosette package is back aboard the ship, the scientists are able to collect water from the bottles for their analyses.  The parameters collected and analyzed during CLIVAR campaigns includes but are not limited to: salinity, oxygen, nutrients, chlorofluorocarbons (CFCs), dissolved inorganic carbon (DIC), total alkalinity, pH, dissolved organic carbon (DOC), helium, and tritium.

Certain compounds, such as some radionuclide (tritium, carbon-14, etc.) and CFCs, can be used as ‘tracers’.  These tracers are used to follow ocean currents and calculate the age of water parcels. CFCs were prominently used in refrigerators and air conditioning units until the 1970s when they were banned over the concern of ozone depletion.  You can learn more about the CFC tracer program here.  Through the WOCE and CLIVAR programs CFC concentrations have been measured all over the world.

Map of global CFC measurements http://www.pmel.noaa.gov/cfc/

Map of global CFC measurements
http://www.pmel.noaa.gov/cfc/

The measurement of pH, total alkalinity and DIC are important for monitoring ocean acidification. Ocean acidification (OA) is the decrease in ocean pH as a result of an increase in carbon dioxide (CO2) absorption by seawater.  OA is a prominent concern in today’s world.  CO2 is pumped into the atmosphere from everyday human activities, such as emissions from vehicles and industrial pollution.  Each year approximately 25% of the CO2 pumped into the atmosphere is absorbed by the ocean.  Although plants can use CO2 for photosynthesis, the increase also has negative implications.  As the amount of CO2 absorbed by the increases, the pH is expected to continue decreasing.

pH time series http://www.pmel.noaa.gov/co2/story/OA+Observations+and+Data

pH time series
http://www.pmel.noaa.gov/co2/story/OA+Observations+and+Data

The pH of the ocean directly affects organisms that form calcium carbonate shells or structures, like corals, oysters, clams and sea urchins.  An acidic environment causes the calcium carbonate to dissolve and makes it more difficult for the organisms to make their calcium carbonate skeletons.  Therefore, it is important that programs like CLIVAR are monitoring global CO2 concentrations (part of the DIC pool), total alkalinity (the ability for the ocean to neutralize acids) and pH.  We know that decreases in ocean pH can negatively impact marine organisms. You can see more about the effect of ocean acidification or marine organisms here.

pmel-oa-imageee_med

Ocean Acidification
http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

As I was conducting some research for this blog post I came across this article that was posted at the Earth Observatory in 2008 about the global carbon budget. I thought it was appropriate to bring it back here.

Earth Observatory article from 2008

Earth Observatory article from 2008

 

References:

http://www.whoi.edu/home/oceanus_images/ries/calcification.html

http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

http://water.me.vccs.edu/exam_prep/alkalinity.html

http://earthobservatory.nasa.gov/Features/OceanCarbon/

http://www.pmel.noaa.gov/cfc/

http://rspb.royalsocietypublishing.org/content/275/1644/1767.full

 

South Pacific Bio-optics Cruise 2014: Stormy weather and radiometry don’t mix

April 9th, 2014 by Aimee Neeley

The NASA FSG folks and the rest of the science crew on the US Repeat Hydrography P16S field campaign have experienced some weather delays, which can be expected when working the Southern Ocean close in time to the Southern Hemisphere winter.  They encountered 45-knot winds (~51 miles per hour) sitting on top of their planned sampling area at around 60 degrees South latitude.  For the safety of all they could not conduct science under those conditions. So they traveled ~200 miles north to escape the weather and then returned southward once the weather had settled.  Below you will see some freeze frame clips from the movie Joaquin Chaves captured showing the large swells and the dramatic gray skies of the Southern Ocean.  The movie was recorded through the porthole, safe inside the ship.

Stormy weather 1

Stormy weather 1

Stormy weather 2

Stormy weather 2

Stormy weather 3

Stormy weather 3

Stormy weather 4

Stormy weather 4

In spite of the rough weather, the FSG fellows have taken advantage of some calmer days to deploy a radiometer.  A radiometer measures apparent optical properties or AOPs.  You might recall from Blog #2 that we discussed Inherent Optical Properties or IOPS that characterize the absorption and scattering (reflecting) of light by dissolved and particulate materials in the water.  The measurement of IOPs can be done at any time day or night.  AOPs on the other hand must be measured during the daytime, preferable when there are clear skies and the sun is directly overhead.  AOPs describe how the light is entering and exiting the water column. Remember that sunlight contains a whole spectrum of colors that are determined by their wavelength.  We see what is called the “visible spectrum” like what is in the image below.

A prism (right) and wavelengths of color (left) http://science.hq.nasa.gov/kids/imagers/ems/visible.html

As the sunlight penetrates the water column, some of the light is absorbed, some is scattered (reflected) backward toward the sky and the rest is scattered forward into the depths of the ocean.  Water itself absorbs most of the red light, so we never really see a red ocean (unless there is something unusual in the water).

The character of the light that is reflected back out of the water can be different than what went in. More specifically, the wavelengths or colors that are reflected back out are the colors that were not absorbed or scattered forward.   Think about when you are at the beach, say Ocean City, MD or Rehoboth Beach, Delaware.  The water typically looks brown or green, right?  This is because particles, including both algae and sediment (and water), are absorbing all of the blue and red light, and the leftover colors of brown and green are reflected back out.  Conversely, for those of you who have seen blue water in places like the Caribbean or around Bermuda, the circumstances are different.  There are very few particles or phytoplankton in the water to absorb the blue light like in the coastal water.  Therefore, that blue color is reflected back out , which is why the water looks so blue and pretty.  A radiometer that the FSG is deploying on this field campaign measures the colors and amount of the light entering and exiting the water column.  The radiometer is hand deployed and, I can tell you, it’s a lot of work!

Joaquin and Scott preparing to deploy the radiometer Photo credit: Isabella Rosso

Joaquin and Scott preparing to deploy the radiometer
Photo credit: Isabella Rosso

Dropping the radiometer into the water Photo credit: Isabella Rosso

Dropping the radiometer into the water
Photo credit: Scott Freeman

 

Joaquin guiding the cable Photo credit: Isabella Rosso

Joaquin guiding the cable; Photo credit Isabella Rosso

 

Mike Novak pulling the radiometer back to the surface Photo credit: Isabella Rosso

Mike pulling the radiometer back to the surface

Satellite instruments, such as SeaWiFS (no longer operational) and MODIS-Aqua (operational) measures this light just like the radiometer so that we can get beautiful images that you can see below.

True color image of Chesapeake Bay http://oceancolor.gsfc.nasa.gov

True color image of Chesapeake Bay
http://oceancolor.gsfc.nasa.gov

True color image of Hawaii http://oceancolor.gsfc.nasa.gov

True color image of Hawaii
http://oceancolor.gsfc.nasa.gov

Our FSG fellas are working very hard during this field campaign.  But every now and then you need to have a little fun.  Mike Novak sent this picture of a snowman that was built on the bow of the ship.  I think the eyes, nose, and buttons are raisins.

DSCN0406

References:

http://ushydro.ucsd.edu/p16s-weekly-reports/

http://www.oceanopticsbook.info/

http://oceancolor.gsfc.nasa.gov

ACKNOWLEDGEMENTS: NASA’s Ocean Ecology Laboratory Field Support Group is participating in the US Repeat Hydrography, P16S field campaign under the auspices of the International Global Ocean Ship-Based Hydrographic Investigations Program (GO-SHIP).  The US Climate Variability and Predictability Program (CLIVAR), NOAA and the NSF sponsor this campaign.

4 logos from CCHDO sponsors

Greenland Aquifer Expedition: Bonjour from Kulusuk!

April 4th, 2014 by Maria-Jose Viñas

By Clément Miège

It might be hard to believe but yes, we are still in town! We have been delayed for a full week now, every day getting ready for a possible flight the next day, and every morning, we get the same message: “Unfortunately, there will be no flight to the ice cap today due to weather and bad visibility with low clouds, but tomorrow looks more promising.” Oh, no! Even if it is fully justified, it is always a bit disappointing the moment you hear that, but I think our team has a good experience already with this kind of delay and we are able to switch quite easily and still be happy and optimistic for a flight the next day.

The main helping factor that puts us back in a good mood comes from the weather forecast. Indeed, every day we are able to see a clear-sky window that makes us think that we will be able to fly the next day. Sometimes, this weather window can be very tiny, but it is always there! Good spirits!

Tomorrow, again, it looks great, with a weather window in the afternoon (Forecast provided by the Danish Meteorological Institute .)

Tomorrow, again, it looks great, with a weather window in the afternoon (Forecast provided by the Danish Meteorological Institute .)

When you look at long-trend forecasts (beyond the following 48 hours), the weather is changing a lot in short spans of time. Often, there are significant changes from one forecast to its updated version a couple of hours later. For example, a 5-day storm, with heavy precipitation, appears in the forecast, but then it it is removed from the next update. So our moods shift quite a bit. For even longer trends, it becomes a different story. Rick shared with Ludo and me his experience with the so-called “Canadian Forecast”. It consists of making the last 5-6 days of a 14-day weather forecast always be nice and sunny, to keep people happy through the winter so they can anticipate the end of it. We can verify this “happy weather trend” in Greenland with our own Danish Forecast — the five last days of this forecast are always sunny. We are keeping a record of the forecast since we arrived two weeks ago, and we can say this is a regular pattern.

After checking weather forecast here, our daily duties are not done yet! Next, we take a look at the data from a weather station that is currently in the field, in our future camp site. We dropped the weather station as part of our cargo last week, but we did not have time to set it up. It is however transmitting data and our IMAU colleagues gave us access to the transmitted data. Unfortunately, the signal for diurnal temperature is getting weak, it’s almost nonexistent anymore, which means that the weather station is getting buried. More and more snow will need to be removed to access our equipment when we will get to camp (maybe tomorrow?) Next, we take a look at the Kulusuk airport’s flight schedule for the day. We can see for example that the Tiniteqilaaq flight is canceled (“aflyst”, in Danish) and that the Isortoq flight is delayed. Then, we do the same thing for the Tasiilaq heliport schedule and then we speculate (while drinking our coffee) where our flight fits in this schedule. We are getting quite good at this exercise! Our flight never fits and we are always rescheduled. But there are some events that are still out of our control. Three days ago, a domestic conflict in Kuummiut required the police Marshall to solve it. Since the Marshall is based in Tasiilaq, the helicopter had to fly him there. That day we had woken up at 5:30 am for a flight scheduled to leave at 7:05, which got rescheduled to 11 am, and after three additional hours waiting at the airport, it eventually became a cancelled flight. Needless to say, the helicopter never made it to the Kulusuk airport. We simply went back to the hotel in the pouring rain. As Ludo likes to say: “This is again craptastic; good times!”

Sunday (March 30) was a beautiful day though, but we were not on the flight schedule — the pilots had to catch up with the Saturday flights had been cancelled. We took advantage of the nice weather to further test our field equipment. As I mentioned in an earlier post we will be testing a low-frequency radar system in the aquifer region on the ice sheet. Laurent Mingo at Blue System, who develops the IceRadar is letting us test a beta version of one of his radar systems. The IceRadar is currently used by many research groups on alpine glaciers, ice caps and ice islands. As such, it has been deployed in many regions of the world (Yukon, Rocky Mountains, Himalaya, Bhutan, Iceland, the Andes, the European Alps…) to perform ice thickness measurements and bed mapping, but also to look at the glacier englacial properties. I believe this is the first trip for the IceRadar to the Greenland ice sheet. So we are quite honored to have this system with us to try it over the aquifer.

Setting up the IceRadar for the first time in Greenland, with the 5 MHz antennas. The lower the frequency used for the radar, the longer the antenna has to be. For a 5MHz system, the antenna length is 20 meters (about 70 feet), and there are two of them (receiving and transmitting). (Credit: Rick Foster)

Setting up the IceRadar for the first time in Greenland, with the 5 MHz antennas. The lower the frequency used for the radar, the longer the antenna has to be. For a 5MHz system, the antenna length is 20 meters (about 70 feet), and there are two of them (receiving and transmitting). (Credit: Rick Foster)

After the setup, we try our radar going from the seasonal snowpack to the relatively thin sea ice – that gives us important changes in terms of dielectric constant, which look quite obvious in the radar profile. The system total length is about 50 meters (164 feet), so no sharp turns are allowed! (Photo credit: Rick Foster.)

After the setup, we try our radar going from the seasonal snowpack to the relatively thin sea ice – that gives us important changes in terms of dielectric constant, which look quite obvious in the radar profile. The system total length is about 50 meters (164 feet), so no sharp turns are allowed! (Photo credit: Rick Foster.)

Getting the 40MHz IceRadar ready, you can see the difference of the antenna size -- this is definitely easier to turn. (Photo credit: Rick Foster)

Getting the 40MHz IceRadar ready, you can see the difference of the antenna size — this is definitely easier to turn. (Photo credit: Rick Foster)

Rick watches Ludo and me maneuvering the IceRadar from the hotel. A new (feline) friend is also observing us, probably wondering what we are doing here! (Credit: Rick Foster.)

Rick watches Ludo and me maneuvering the IceRadar from the hotel. A new (feline) friend is also observing us, probably wondering what we are doing here! (Credit: Rick Foster.)

At the end of the day we have great news: the IceRadar is working well at the two frequencies tested, which is really promising toward our ice sheet measurements. YAY!

Finally, the hotel still does not have running water. As Ludo mentioned in an earlier blog post, the heating element in the water pipe supply line that prevents the water from freezing broke. And the road to get to the lake with fresh water is still being plowed, but the bad weather and drifting snow prevent the plow truck from making much progress. We are getting used to showering with a water bucket and becoming more and more efficient at conserving water.

Transferring water into bottles for drinking (Photo credit: Rick Foster.)

Transferring water into bottles for drinking (Photo credit: Rick Foster.)

Without water at the hotel, we are even more motivated for going to the ice sheet since we know we will not be missing a good hot shower anyway.

Our team has a really good feeling for tomorrow, so let’s hope for a “go” and keep our fingers crossed!

Cheers, Clément on the behalf of the aquifer team.