Posts Tagged ‘atlantic ocean’

Stubbins joins Arctic cruise

June 19, 2012

Skidaway Institute scientist Aron Stubbins has spent the last couple of months working in Germany. He reports in on a cruise he is about to join.

I’m off to the Arctic on Germany research vessel Polarstern.

I will be collecting samples to determine the export of dissolved black carbon from the Arctic to the Atlantic Ocean. The cruise will transect Fram Strait, the major gateway for the exchange of water and dissolved material between the two ocean basins. Today we will leave Bremerhaven in Germany, site of the Alfred Wegener Institute which houses the R/V Polarstern.

In a few days we will reach Svalbard and begin a transect from there towards Greenland following 78.5 degrees north. During this transect we will first cross the West Spitsbergen Current (WSC) which carries warm Atlantic waters north into the Arctic Ocean. This is the northernmost extent of the Gulf Stream that originates in the Gulf of Mexico and travels past Georgia and Savannah at the edge of the Georgia shelf.

We will then transit west towards Greenland, breaking ice as we go. In this part of the cruise we will collect water samples from the East Greenland Current (EGC). This carries cold, polar water south into the Atlantic Ocean. A figure of the currents is shown at http://www.whoi.edu/science/PO/people/pwinsor/project_ao02.html.

My work will look at the amount and type of dissolved organic carbon that these two massive currents carry north (WSC) and south (EGC). Our progress can be followed in real time at http://www.awi.de/en/infrastructure/ships/polarstern/where_is_polarstern/. This site will also post weekly updates about life and science aboard R/V Polarstern.

The cruise will end in Longyearbyen on Svalbard where I will collect some samples to continue ongoing investigations into the sources and nature of glacier carbon (http://www.skio.usg.edu/?p=research/chem/biogeochem/glaciers).

Advertisements

Skidaway Institute, Georgia Tech-Savannah partner on phytoplankton research

April 18, 2011

Sometimes scientific advances provide answers, and sometimes, they simply present more questions. That is what happened when scientists began using satellite imagery to study the ocean.

When Skidaway Institute of Oceanography scientists Jim Nelson and Catherine Edwards looked at satellite imagery of the ocean off the Carolinas, they noticed persistent blooms of phytoplankton, an important part of the marine food web. These mysterious blooms occurred during the winter along edge of the continental shelf off Long Bay — located between Cape Romain, South Carolina and Cape Fear, North Carolina. Phytoplankton blooms like those observed off Long Bay can provide a considerable boost to the bottom of the food chain, with significant implications for fisheries.

“The immediate cause of the blooms is an input of nutrients, like nitrogen and phosphorous, associated with transport and mixing of deep, cold onto the continental shelf,” said Edwards. “The Long Bay blooms persist for weeks or even months during the winter, suggesting multiple modes of nutrient input.”

Two of the guiding questions are why this feature is so persistent over the winter, and what are the dynamics that sustain this bloom?

Edwards and Nelson are teaming with Harvey Seim from the University of North Carolina and Fumin Zhang from Georgia Tech-Savannah on a project to answer those questions. The project is funded by a $1.6 million grant from the National Science Foundation supporting a team of scientists from all three institutions. With the help of Skidaway Institute research coordinators Trent Moore, Julie Amft and Charles Robertson, the project team will deploy moored and mobile instrument packages and conduct shipboard surveys to test hypotheses of how the winter blooms are formed and sustained.

The team will use some cutting-edge technology that will enhance its ability develop a clear picture of what is happening. This includes instrument packages mounted on moorings; mobile, autonomous “gliders”; underway ship surveys; standard ship-based station sampling; and satellite measurements of sea surface temperature and ocean color.

Skidaway Institute researchers (l-r) Catherine Edwards, Trent Moore, Julie Amft and Jim Nelson examine a glider.

Three moored packages will be deployed to provide continuous measurements of water properties and currents through the winter months. One mooring will be placed at 35 meters of depth, the approximate position of the shoreward edge of the winter bloom.

Two more packages will be placed in approximately 75 and 150 meters of water, with the 75 meter mooring equipped with an instrument package called a SeaHorse. Powered by wave motion, the Seahorse moves up and down its mooring wire, taking measurements throughout the water column. A telemetry system in the surface mooring periodically reports its observations.

The research team will also use another high-tech tool, autonomous underwater vehicles, also called gliders.

Skidaway Institute researchers lower a glider into a tank of water to adjust buoyancy and trim. (l-r) Trent Moore, Dongsik Chang, Charles Robertson and Julie Amft

Two of these torpedo-shaped vehicles, equipped with sensors and recorders, will provide the ability to collect observations under all conditions, including during winter storms when ship operations are not possible. The gliders will survey across the study area, taking and recording measurements as they go. From time to time over the four to five week missions, they will surface, report their data by satellite phone and receive instructions as needed.

The gliders will be controlled from shore with an autonomous glider control system co-developed by Fumin Zhang at Georgia Tech Savannah. Two Georgia Tech-Savannah graduate students, Klimka Szwaykowska and Dongsik Chang, are developing algorithms to optimize the glider sampling given real-time data collected by satellite, the SeaHorse profiler and the gliders themselves.

Catherine Edwards (r) and Dongsik Chang work on the tail of a glider while Klimka Szwaykowska looks on.

Members of the research team will spend much of the winter of 2012 aboard the Skidaway Institute research vessel R/V Savannah, conducting experiments and collecting data.

Armed with a better understanding of the physical processes that “fertilize” the outer shelf and how phytoplankton take advantage of the nutrient input, the research team will be able to answer larger questions about how biology and physics interact in Long Bay.

The project will run for three years.

Update From the Gulf Stream: No Tarballs or oil found in quick survey

June 28, 2010

Professor Jay Brandes wrote this report from a short research cruise to the Gulf Stream this past weekend.

This last Friday-Saturday, I had the opportunity to tag along with a group of 15 K-12 teachers and Dr. Marc Frischer, who was leading them on a cruise out to the Gulf Stream.  It was to be the highlight of a weeklong intensive workshop on ocean literacy for the teachers, and the first time that many of them had been on a ship out of sight of land.

R/V Savannah pulling away from the dock.

I came along to do a little preliminary reconnaissance for possible traces of oil and for plastics in the South Atlantic Bight region.

There has been a considerable amount of concern about oil being carried by the Gulf Stream / Loop Current (see previous posts) from the Deepwater Horizon Spill. While no satellite imagery or other data has suggested that large amounts of oil has reached the Gulf Stream, it is always possible that smaller amounts could have been carried into the current.

Thus it makes sense to take a look for oil traces. Given the timeframe of the cruise (leaving at 4 pm Friday, getting back at midnight Saturday night) there wouldn’t be enough time to conduct an exhaustive survey. However, there was enough time to do a few quick tows. In addition, I wanted to see how much plastic contamination might be out there. Most of us have seen the reports on the “great Pacific Garbage Patch”, and there is a lesser one out in the middle of the North Atlantic as well. But little data exists for out coastal waters.

Unlike the sheets of oil seen in the Gulf, the oil reaching our region is expected to be weathered and broken up into smaller pieces, called tar balls. If they are widely spread out, as expected, then the best and fastest way to collect them (or search for them) is to use what is called a “neuston” net. Neuston refers to organisms living at the sea surface. Such a net is designed be towed behind or beside the research vessel, right at the surface. Scientists also have used such nets to collect floating plastics in the ocean.

We conducted four surveys, towing our net for a half hour in the middle of the Gulf Stream, its edge, the outer shelf, and the middle shelf. We found no tar balls or other oil residues in any of the samples, which was a relief. While I have to caution that these were just small surveys (the net is only 2 meters wide by 1 deep), and it is a big ocean, the lack of any sign of oil is at least a positive sign.

Some of the Gulf Stream plastic

However, the same could not be said about plastics. We found small plastic pieces in all of our net samples, ranging from 1-2 mm size tiny particles to larger pieces a few cm across. One would not see these in looking out from a boat, unlike the big pieces found in the “garbage patches”. But they are of a size that will interfere with marine organisms, because they can be ingested.

Overall, the levels of plastics were low, and I feel that I can describe our offshore environment as relatively pristine, from this standpoint. It is up to all of us to keep it that way.