Ocean Exploring - what are we really doing?

The storm is finally moving away, success! We have spend the last few days on the Florida escarpment for some additional mapping in order to avoid the worst of the weather, and after some rough days at sea we just arrived back to the area around Deepwater horizon to continue our mapping mission. Fortunately I have not been seasick, but the wave action gets you pretty tired so we are all glad that the sun is shining and that the ship is rolling gently with the swell.

Celebrating good weather on our back porch!

Here is a little something for you who wonder what we are actually doing out here. It gets a bit technical at times so I put a short wordlist in the end if you get lost...

The Okeanos Explorer is equipped with an array of sensors, sonars and ROV units (its really quite awesome if your into nerdy ocean tech stuff). The main objective of this expedition is to learn more about how to map and detect gas seeps in the Gulf of Mexico using a state of the art multibeam sonar EM302(1), a splitbeam sonar EK60(2) and a Knudsen sub bottom profiler (3).

Live image from our multibeam sonar EM302 showing naturally occurring gas seeps from the
seafloor at Biloxi Dome, an area close to the Deepwater Horizon site.  The colorful window at the top shows a model of the seafloor and the location of the ship. The lower (grey) image is a slice of water column data -in this image showing two gas seeps and the deep scattering layer (7).  Image credit NOAA/OER.

Live image from the EK60 showing 1000 m high gas plumes at Biloxi Dome in the Gulf of Mexico. The image represents 1 hour of data from left to right starting at sunset. At this time tiny phytoplankton (6) eating creatures, fish and possibly sea monsters  move up from the ocean depths, as deep as 1000 m, to feed. This daily migration by the deep scattering layer (7) is how I know that it is evening in my little computer world inside the science control room (kind of sad i know...).  If you look at the top 500 meter of the image this is what you see.  Image credit NOAA/OER.  

We also use a CTD (4) with a flourometer to map salinity, temperature, oxygen and fluorescence (5). The CTD is attached to a huge winch with 9000 meter cable for deep water measurements, thats a lot of wire (enough for a vasalopp)!

CTD measurements in perfect weather just before the storm rolled in.

NOAA Corps Officer Glen Rice about to deploy a lethal XBT cast! In order to measure the speed of sound in the water profile we make daily measurements of sound velocity.

During the initial response of the oil spill, the area was throughout mapped using an EK60, so one of the questions for this trip was if we can use the data from the EM302 to faster map a larger area and with more detail compared with the EK60 in order to better understand the naturally occuring background levels of gas and oil leaking out into the Gulf.

Standing on the deck looking over the sea I have unsuccessfully tried to imagine that the EM302 sonar is mapping up to 3 km of the seafloor on both sides of the ship (6 km swath) which is about 90 % of what I see from my point of view on the boat (my approximation...), and that the seafloor is 2-3 km below me. its really quite amazing that it works. 

 Using all these instruments we have found numerous gas seep sites and have also been able to correlate many of the gas seeps with EM302 bottom backscatter (8) images from the seafloor. These images seem to be showing calcium carbonate hard ground around a majority of the seeps. The calcium carbonate are formed by bacteria feeding on the gas comming up through the sediments. The bacteria and the substrate they form feed and provide habitat for a whole eco-systems teaming with colorful life down in the dark deep water around some of these seep sites. During this trip we will not do any ROV(9) work, but there are plenty of images from other expeditions showing really cool stuff down there (I am assuming that if you have reached this far in my text there is some sort of bio/science nerd in you).

Photo from an earlier ROV survey in the Mexican Gulf showing flourishing life near a deep water gas seep.
Photo by Ian Mac Donald, Image credits NOAA/OER and BOEMER  

Enough of school for today, and also time for me to stop writing on this essay... It is only 4 days left until we reach Pascagoula on saturday morning, time fly too fast. Although I am really looking forward to spending a couple of days with Anna in New Orleans. Now sleep, tomorrow more seeps!


Some links you might find interesting

Okeanos Explorer ship tracker and live data viewer (you can see the data we collect in near real time!): http://www.ncddc.noaa.gov/website/google_maps/OkeanosExplorer/mapsOkeanos.htm

NOAA Ocean Explorer: http://oceanexplorer.noaa.gov/welcome.html

Okeanos Explorer, the ships webpage: http://www.moc.noaa.gov/oe/

Wordlist (Warning, you might end up with more questions then you came here with)
1. EM302 - a deep water multibeam echosounder with 288 physical sound beams capable of detailed mapping of a wide swath of the seafloor and water column.
2. EK60 - Similar to a single beam echosounder, but with 4 receivers in order to determine precise targets strengths and position in the sound beam - often used by fisheries and scientists to identify and map schools of fish.
3.  Sub bottom profiler - Low frequency sonar penetrating the seafloor in order to get profiles of sediment layers and rock.
4. Phytoplankton - The little green guys at the bottom of the food chain living of sunlight and nutrients. 
5. CTD - device measuring salinity temperature and depth.
6. Flourometer - device measuring fluorescence which can be correlated to the concentration of phytoplankton in the water, but it was also used during the oil spill to indicate the presence of oil in the deep water.
7.  Deep scattering layer - A layer made up by various zoo plankton and fish that due to their swim bladders used for their daily migration to the yummy surface waters, is clearly visible on echosounder images, 
8. Backscatter - Shows the strength (amplitude) of the returning sound from each target. Strong bottom backscatter indicate a hard seafloor that reflect sound well, weak backscatter indicating a softer seafloor substrate. 
9. ROV - Remotely operated vehicle, often equipped with a video camera and a variety of tools.