Journal

In a word, wow!

South Georgia
South Georgia by sunrise. What an amazing way to start the day, and what a glorious sight.

South Georgia coastline
Notice the glacier encroaching upon the ocean.

Today started with a glorious view of South Georgia. The sun was shining, the sea fairly calm, and the science party a go for GPSA Global Positioning System (GPS) is a satellite-based navigation system used to track the location or position of objects on the Earth’s surface..
Decisions were made, the zodiac was loaded, and by 6:30 am the science party was: two marine techs from the vessel and four scientists.

Team leaving to check out GPS locations
After arriving on station key members of the science party head out on a zodiac to scout out a GPS station location.

Similar to explorers from the past, this was a scouting party: their goal to find an ideal location for the southeastern most GPSA Global Positioning System (GPS) is a satellite-based navigation system used to track the location or position of objects on the Earth’s surface.. An hour and a half later the intrepid adventures returned, sadly with no location. The rock face on the island was too steep and too difficult to reach by a small rubber boat, the sea swell and wind off the glacier made landing too dangerous. As a reminder, we are scouting locations to set up a GPSA Global Positioning System (GPS) is a satellite-based navigation system used to track the location or position of objects on the Earth’s surface. station to record minute changes in the movement of the South Georgia micro continent.

Ian Dalziel chief scientist
After being in the zodiac for over an hour, our chief scientist Ian Dalziel returns wet, cold, and in perfect explorer form: with a smile on his face!

Zuni Hills Grizzlies
A great big shout out to the Zuni Hills Grizzlies! Thanks for following along all the way from Arizona!

With the GPSA Global Positioning System (GPS) is a satellite-based navigation system used to track the location or position of objects on the Earth’s surface. put on hold for another day, we have left the island, heading offshore to at least one thousand meters before we can start the seismic. As with all science there is a great deal of preparation: electronically, inside the Palmer with computer programs designed to collect, interpret, and then decode the data, so that the scientists can see the sea floor. There are also deck preparations: both the streamer and the air gun umbilical (source).

Air Gun Umbilical

Air gun seismic apparatus
Setting up the air gun seismic apparatus: half of the seismic operation.

Let’s start with the source, the air gun umbilical. This piece of the equipment generates the sound wave, with high pressure compressed air in the umbilical. The “guns” literally shoot a ball of compressed air, which in turn displaces water moving towards the ocean floor. Once hitting the ocean floor, this pressure wave then heads back to the ocean surface. The time it takes for this wave to hit the ocean floor and return (documented by the streamer) is the data the scientists are looking for. Once the raw numbers are placed in differing computer programs, the scientists end up with a map of the ocean floor.

Streamer

The Streamer
If you look closely inside the tube you will see the lighter than water, environmentally friendly gel in which the electronic components are placed for optimum efficiency.

The streamer is similar to a long hose, and inside this hose are 72 hydrophones (in groups of three called channels). A hydrophone is an underwater microphone that we will be using as a receiver of the pressure wave after it has bounced off the ocean floor (the ship's ear). Each of the 24 channels (three hydrophones each) is designed to get an independent signal for better data definition. In simple terms, each hydrophone is designed to hear the sound wave after it bounces back to the ocean surface.

Both the streamer and air gun seismic run in parallel lines in the water off the rear (aft) deck of the vessel. The air gun seismic will play out to about 50 meters and then the streamer and its receivers (channels) will trail after. Again, I give thanks to Bud who is our resident artist, in helping me to understand the intricacies of seismic survey geometry.

An illustrated drawing of the seismic array off the back deck of the boat
Learning is always enhanced by visuals. In this case, how the seismic will look and what it will accomplish once in the water.

Sadly, after all the preparation for running the seismic, the seas picked up and operations were cancelled. The weather has been our nemesis, and today the wind gods won. There were however moments of calm, times when work was accomplished and great feelings of satisfaction ensued.

Zodiac off the starboard side
In the tradition of explorers past, members of the scientific party leaving on expedition, searching for the ideal GPS location.

See everyone tomorrow for another adventure on the high seas… literally.

Details
Author
Jillian Worssam
Date
Location
South Georgia
Expedition
Sea Floor Changes and the Antarctic Circumpolar Current

View Comments

Comments

Sat, 10/04/2014 - 05:26

Jillian Worssam

Hi Richard, Thanks for writing.
The umbilical is made up of several components.

There is a strength member that provides the mechanical connection
between the ship and the guns as they are towed astern. The strength
member is a 3/8" diameter 12 strand rope made of a high strength plastic
fiber called dyneema. Each end of the rope has an eye spliced with a
thimble. The thimbles are made of stainless steel.

There are air hoses to plumb the high pressure air from the ships
compressor to the guns. There are 3 hoses in the umbilical, one for
each gun. The hoses are made of a thermo plastic with kevlar
reinforcement. At the ends of each hose are fittings. These fittings
are made of stainless steel. The hoses are about 1/2" diameter on the
outside. These hoses are designed to handle the 2000 psi pressure.
This is extremely high compared to pressures in everyday life. Your
bike tires are at about 50 psi maybe 100 psi. Car tires around, 35 psi.
The water in your house is 30 psi to maybe 80 psi. Not only does it
need to withstand the internal pressure but it needs to survive the
shaking each time the gun fires.

There are electric cables to send and receive signals to and from the
guns. There are 3 cables per Gun for a total of 9. These are a
stranded copper conductor with plastic insulation. The plugs at the
ends are a special water proof design, they are plastic with lock rings
made of plated brass. These cables need to withstand the violent
shaking each time the gun fires. This is why the copper is in many
strands, making it more flexible. The plastic insulation needs to
provide some strength but mainly abrasion resistance. Any hole or crack
in the insulation would short the electric circuit, causing a
malfunction.

All of these Cables and Hoses are twisted to form a rope. The spaces
between the hoses and cables are filled with rope to give an overall
round cross section. The filler rope is made of polypropylene. Then
all of this is covered with a jacket also made of polypropylene. This
is the orange color you have probably seen in pictures. Polypropylene is
a plastic that floats and is abrasion resistant. The rope and jacket
are not so buoyant as to float the whole umbilical but they help to make
it lighter in the water.

The other important aspect of these materials is their resistance to
corrosion. Plastic, Stainless steel, and plated brass all stand up to
salt water quite well. Other materials like steel would rust away.

Good Question, keep 'em commin'

Jeremy Lucke, Marine Tech

On 2014-10-03 08:04, webmaster@polartrec.com wrote:

Tue, 09/30/2014 - 13:05

Rosemary Groves

Just wow!!! What a glorious view. And it's amazing!!

Tue, 09/30/2014 - 15:31

Blanca (you ca…

Is the seismic gun shows the plaques? And their movements? The pictures are wonderful! Thank you Jillian for educating us all!

Wed, 10/01/2014 - 16:32

Susan Steiner

Have been following every minute of this...just so great! It seems like the air gun thing is pretty complex, is there a maximum depth that it can handle? sorry if you've mentioned that already...I've mainly been following your quests on the bow for awesome wind and energy!! love the smile on the chief scientist's face!

Thu, 10/02/2014 - 05:17

Jillian Worssam

Hi Susan, Great question, and I had not yet talked about the possible maximum depth. The scientists work at keeping the air guns psi at 2000,
and they have amazing resolution to 2000 meters. They can shoot to 4000
meters but the resolution decreases and loose definition. With the
seismic they are looking for details, and the resolution is very
important. With the multi beam the scientists are predominantly looking
at the sea floor, not underneath so for the multi beam, salinity the
ships velocity and temperature will come in to play as with that
instrument they just want the distance to bottom, not down to the crust.
I hope I haven't jumbled up the answer. Thanks for asking. Jillian

On 2014-10-01 17:32, webmaster@polartrec.com wrote:

Tue, 10/07/2014 - 12:52

Shiann in alm…

What did you hear with the hydrophone?

Wed, 10/08/2014 - 02:42

Jillian Worssam

Hi Shiann, Thanks for the great question. The hydrophones we are using are on the streamer, so we are not listening with our ears, but
listening with a computer. The data is coming into the computer and
then the scientists have computer programs to decode the data into
information that they can use. We are specifically listening to hear
the distance to the sea floor. On other research cruises if people are
studying marine mammals they might use hydrophones to hear the
vocalizations. Thanks again for following along. Jillian

On 2014-10-07 13:52, webmaster@polartrec.com wrote:

Fri, 10/03/2014 - 07:04

Richard Szal

What kinds of materials were used to build the air gun umbilical?

Tue, 09/30/2014 - 07:27

Janet Warburton

That's a great way to start the day! I'm so glad that the team was able to get off the ship for their work. Sounds like you have a rough day or two ahead. Great journals and the photos are coming in nicely. Thanks for the postings!
Janet