sea90E - an oceanographic expedition to the Indian Ocean



	High.Seas.HIGHTECH/analyze!ocean@voyages by Lara Kalnins, Christopher Paul, Jeff Laughlin, Amy Eisin and Rory Wilson In this short article, we will give you a quick glimpse into how technology helps with science on the high seas. We have come a long way from the early beginnings of ocean research. Ships initially used a leadline to find the depth. They took a chunk of lead, coated it with grease or tar, attached it to a line marked in fathoms (six feet) and lowered it to the bottom. When the line went slack, they could read how far out it went and when it came up, they could get an idea of what was on the bottom, (sand, mud, clay..) So now we use the multi-beam instead of the line to see how deep it is. We use seismic's and the dredge to see what is on the bottom. What do we do with this information once we have it. The immediate use in the past for the lead line was help ships navigate when they were in coastal waters, and keep them off the bottom. We still use the multi-beam for that, and as you can but we also store this information for later use. The main use of all this data is to make maps! On board the Revelle, we have several forms of maps, or charts. These are used to pilot the ship in through waters by knowing, in advance, the depths are each place. These maps are made by collecting and cross checking information from several sources, including expeditions like this one. In the earliest days, map-makers like Gerald Mercator and Abraham Ortelius used logs and reports by ships to make maps. Considering their information, their maps were fairly accurate, and Mercator devised a mathematical calculation that let map-makers draw a flat map of our round world by stretching the upper and lower sections of Earth. This worked well enough that we still use this method today. Now our data sources are better, and we will look at how we use computers to make better bathymetry maps and to check our data. A first large scale source of map data for the oceans is the gravity image files made by satellite photos. This is known as he Sandwell an Smith data files and is reasonably accurate to 1 mile on the Earth, (1 minute of latitude) The data file to store all this information is less than 1 gigabyte, well within the size that is workable on most desktop or laptop computers. The most common data format in modern use is called GRD, gee, that sounds like a grid, or network of lines.. It is. This grid format is used by a really cool program called GMT that lets researchers like Chris make highly specialized reports for science expeditions like this one. This was the track of our survey on the 90 East Ridge for the early weeks of our trip. Chris uses the large scale Sandwell and Smith data to make the main blue and green parts, and then he adds more information to make the concentrated parts that we are surveying in depth. This includes the multi-beam data the lets us see a detailed section on both sides of the Revelle as we survey a section that is of particular scientific interest. For example: In the map section at right, points A & B are in an area that has a seamount and was the prior site for ocean drilling. There was not an accurate map of this area and we wanted to collect additional samples of rock here so we could date this region. So what is next? Well, this is where Chris now will take the collected data back to Texas A&M and further combine and analyze the information. The actual processing for each day or area would take only a couple of weeks, but this information will be analyzed and interpreted by Chris and a wider group of scientists who have exclusive access to this information for up to two years. Part of our research goals for this expedition was to build on prior work for the 90 East Ridge. For example, Oleg, a scientist from Russia, has been involved in many ocean expeditions. As a part of his research, he has access to much of the mapping and seismic surveys conducted in the past by Russian scientists. Our geophysicists are working together to share and combine this information. The work goes on! In this photo, Amy, Lee and Oleg are looking at the seismic data monitoring equipment. Amy Eisin is looking at a different view of the information collected by the seismic equipment. In the detailed, very large data files that are collected by this gear, there is a wealth of information about the composition of the bottom. There is so much data that analysis is even more complex. People have written custom software for particular purposes. For example, oil exploration may look for certain critical features within layers of sediment that may indicate pockets of particular resources.. ok, like oil! Drill ships have teams of quite important people looking carefully for pockets that may indicate build-ups of methane gas, which, if hit by a drill ship, could cause an explosion. We are looking for something a bit different in our survey; we are looking for areas that may indicate a shift or jump in the underlying structure of the hotspot trail. We have found some significant features already, and further analysis may teach us more. But one drawback of doing something somewhat different from what software is primarily intended for is that it is prone to errors. RED marked, unknown, strangely worded errors... Semi-custom software is usually not well documented since it was written by specialists for a narrow purpose; the specialists then moved on to new projects. The software may still be useful, but often requires lots of trial & error, maybe some frustration, and midnight calls to technical support! There is yet further use of the information that we are collecting our here. Lara takes the information, and based on computer programs that she designs, she looks at models based on the data. She actually builds a miniature world that represents the geology and then looks at how it can help us interpret the seafloor. If we know one area, have data for part of it, maybe we can develop a model that will help us to "estimate" what another area looks like that we have less data for. Isn't that cool? She uses a language called Perl to write computer programs, sometimes uses C, or C++, occasionally AWK and other elitist software tools for this work. World-wide, there are only a few dozen people that have this level of programming skills for modeling geophysics data! So, a couple of specific things about the hardware and computers here. The seismic files are large, no... huge. A tiny time slice that was used to send to technical support was about 100mb. Chris has about 500 gigabytes of data for this survey. The computers that are used to process this are fairly powerful. Take a computer, load it with lots of RAM, as much hard disk space as possible, load Linux and you have a minimal analysis machine. On the ship here, there are racks of computer equipment, networking routers and switches and the satellite. We use a satellite to communicate to shore, and this is the limiting link for communication. The equipment and the space on the satellite are both expensive, so this is carefully used. There is also a firewall so that the science and ship data is not available unless we need to send it somewhere! To sum it up, it is a complex computer environment and is in use 24 hours a day. This is the satellite mounted on the upper deck above the bridge. The base is almost 70 feet above the ocean. You can just see Jeff climbing up the access ladder in back. We went up to inspect the equipment. Three of us could easily go up inside the fiberglass shell. All right, it is back to working with the data. Just wanted everyone to see how much the world has changed with computers to help analyze the information we collect! updated August 1, 2007 from the Indian Ocean
			High.Seas.HIGHTECH/ analyze!ocean@voyages, by lots of us... How to Become a Captain, by the Captain The Search for the Indo-Pacific Humpback Dolphin, by Leslie Nemazi. Rocks Rock! (or ) The Fresh Cut Surface of Beautiful Ocean Rock, by Evelyn Mervine Exploring the Bridge of the RV Roger Revelle Dredging Operations onboard the R/V Revelle, by Amy Eisin Geochemistry of Volcanic Rocks, by Fred Frey Cool Expedition Discoveries Already!, by Will Sager Anatomy of a Seamount Survey, by Will Sager M agnetometers (“Maggie”) and Attracting Sharks, by Rory Wilson Acoustics: Substitute for Superman Vision?, by Will Sager What is Bathymetry?, by Will Sager Hotspots and Ninetyeast Ridge: What’s a hotspot?, by Will Sager