What’s up with GP15?

“GP15” is the code name of this GEOTRACES research expedition from Alaska to Tahiti. GP15 draws a vertical line down the middle of the Pacific Ocean at longitude 152° West. The 67-day voyage aboard the Research Vessel Roger Revelle spans more than 5,000 miles of ocean.

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Clouds off the stern of the Research Vessel Roger Revelle near Vancouver Island. Photo: Alex Fox

“GP15 is like the Pacific Ocean’s greatest hits album,” says Co-chief Scientist Phoebe Lam of the University of California, Santa Cruz. “If you were going to choose one track to understand every major ocean process, this would be a strong contender.”

This expedition is a study of extremes. It begins collecting samples of seawater in the marine equivalent of a rainforest and ends in an underwater desert.

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The path of GP15 along longitude line 152° West. Each dot represents a station where the expedition will pause to collect samples. The different colors indicate how many measurements must be retrieved from each station. Red dots are “Super Stations,” which take multiple days to complete. Blue and purple dots are different kinds of “Full Stations,” typically requiring 24 or 36 hours. White dots are “Demi-Stations,” that can be completed in less than a day. Finally, green dots are places the R/V Roger Revelle will stop in port. Image: GEOTRACES

The waters off Alaska are filled with microscopic plants called phytoplankton. They are what drive Alaska’s productive fisheries and are the dinner bell to which giant whales are drawn. But phytoplankton depend on abundant nutrients like nitrogen and rare trace nutrients like iron to turn the sun’s energy into food. GP15’s investigations will probe where exactly those nutrients and others can be found, how abundant they are and where they’re coming from.

Tahiti may be known for rainbow studded coral reefs, but the ocean surrounding those reefs is crystal clear precisely because it is so devoid of nutrients. Without abundant nutrients, phytoplankton become scarce and different ocean processes come into play, all of which will be captured by GP15’s samples.

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A sunset at sea from the bridge of the Roger Revelle. Photo: Kenneth Olsen

Bookended by these two divergent undersea ecosystems, GP15 will chart how one extreme transforms into the other. Along the way, the 37 scientists aboard the Roger Revelle will sample water that hasn’t seen the sun in 1000 years, pass by hydrothermal vents—thought to be a potentially significant source of iron—and skirt a hotbed of deep sea mining activity.

Deep sea mining has the potential to stir up toxic trace elements, and this GEOTRACES expedition is perfectly positioned to take a chemical snapshot of these waters before any underwater excavation begins. An unbiased baseline of the area’s ocean chemistry will ensure that the environmental impacts of deep sea mining can be laid bare.

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Members of the science team work around the clock to make the most of GP15’s time at sea. Photo: Alex Fox

The data collected on GP15 will complement the findings of the last GEOTRACES expedition, conducted in 2013, from Peru to Tahiti—the horizontal to GP15’S vertical line.

At a time when the world’s climate is changing ever more rapidly, the oceans remain a bellwether. The oceans absorb more and more carbon dioxide and heat every year, and unless large scale studies like GP15 continue, the consequences may blindside humanity.

GP15 blog posts written by Alex Fox unless otherwise stated.

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GEOTRACES GP15 is supported by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this material do not necessarily reflect the views of the National Science Foundation.

What is GEOTRACES?

This expedition from Alaska to Tahiti is part of the GEOTRACES research program, but what does that mean?

GEOTRACES is a global collaboration of oceanographers seeking to better understand ocean chemistry. “We are like the CSI of oceanographers,” says Co-chief scientist Phoebe Lam of the University of California Santa Cruz.

“Events and processes in the ocean leave behind chemical clues. GEOTRACES is about finding them, using them to reconstruct what happened and, ultimately, better understand how the world works.”

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Members of the GEOTRACES GP15 science party and crew coordinate deck operations aboard the Research Vessel Roger Revelle en route to Alaska. Photo: Alex Fox

The clues GEOTRACES focuses on are called trace elements and isotopes. These chemicals can be nutrients, tracers of current and past ocean processes or contaminants from human activity. Where they go and how long they take to get there impacts the global climate as well as the ocean ecosystems humans depend on.

GEOTRACES scientists hunt down these clues on oceanographic research expeditions all over the world. Scientists from 35 countries have contributed to the program. The expeditions crisscross the globe along carefully considered routes designed to capture the full range of ocean conditions—from deep to shallow and from huge plankton blooms to turquoise marine deserts.

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Yellow lines represent completed expeditions, red lines are planned expeditions (including GP15) and black lines are expeditions completed as part of a collaboration with another research program. Image: GEOTRACES

Reconstructing ocean events and cycles from the chemicals in seawater requires knowing how much of some element can be found in a given part of the ocean, but also figuring out how it got there and where it’s going. Understanding what drives the existing patchwork of elements in the ocean can also allow scientists to predict how those patterns and cycles might change in the future.

Another distinguishing feature of GEOTRACES research expedition is that they study a wide range of trace elements and isotopes all at once. “With GEOTRACES you have all these different scientists measuring very specific things, and they’re important, but when you join all the data together the whole is much greater than the sum of its parts,” says Chief Scientist Greg Cutter of Old Dominion University. The full suite of measurements provides context that allows for a richer interpretation of any one stream of data.

Despite knowing how important these chemicals are to marine life, in many cases little is known about where they come from, where they’re going, how they get there and what chemical reactions occurred along the way.

GEOTRACES attacks this knowledge gap by studying the distribution and movement of these key trace elements and isotopes at the global scale.

What are trace elements?

Trace elements are rare by definition, but some trace elements are essential nutrients for living things while others are toxic. For example, both humans and phytoplankton, the microscopic marine plants at the base of the ocean food web, need iron. Without iron, humans become anemic and phytoplankton can’t use sunlight to grow. On the other hand, heavy metals like lead or mercury are toxic.

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Chief Scientist Greg Cutter secures the GEOTRACES CTD Rosette, one of the most important instruments on board. Photo: Alex Fox

“Just like the plants in your garden, certain nutrients are needed for plant growth in the ocean,” says expedition Co-chief Scientist Karen Casciotti of Stanford University.

“We’re interested in what controls the delivery of those nutrients, because they can help us understand why there are huge booms of marine life in some places but not others,” says Casciotti.

In the ocean, iron can be the difference between a saltwater desert and a feeding bonanza complete with whales, fish and seabirds. On the global scale, the presence or absence of these rare nutrients limits how much life the oceans can support and helps determine where it is found.

This has very real consequences for humans as well as whales and fish. A productive year in the oceans could mean a boost to the global fishing economy, but it also helps determine how much carbon dioxide is absorbed by the oceans each year.

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Pacific white-sided dolphins take flight alongside the Research Vessel Roger Revelle. Photo: Kevin Cahill

When phytoplankton turn sunlight into food they suck up carbon dioxide, one of the primary greenhouse gases contributing to climate change. But phytoplankton also need iron to make the chemical reaction, called photosynthesis, go. An ocean full of carbon dioxide is no use without iron. By limiting the amount of carbon dioxide phytoplankton can use for photosynthesis, trace elements like iron can influence global climate.

The importance of trace elements as nutrients is well established, but where they are and how they got there is in some cases a mystery. To trace the path of these essential trace elements chemical oceanographers can use isotopes.

What are isotopes and what do they have to do with oceanography?

Many elements on the periodic table have isotopes—atoms with the same name and chemical properties, but different masses. Their non-standard masses make them distinctive and allow them to be picked out by scientists looking to do some chemical detective work.

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The scientists of GP15 each collect their share of seawater brought up from the depths by the CTD Rosette. Photo: Alex Fox

When isotopes are radioactive, they can be used like stopwatches. Their predictable rates of decay allow scientists to infer how long it took the radioactive isotope to get where it is or how long it has been there.

Other isotopes can be used like fingerprints that identify their source. For example, certain isotopes only come from underwater cracks in the earth’s crust called hydrothermal vents.

A third use of isotopes is as a way of tracking chemical or biological processes. For example, some organisms prefer one isotope over another. So, if an oceanographer sees a certain ratio of isotopes in the water, it tells them something about what various marine critters are up to.

GEOTRACES seeks to establish the distribution of key trace elements and isotopes in the ocean while also uncovering the processes that brought them there. This approach has the power predict the patterns of marine life these elements underpin, as well as the ocean’s responses to our rapidly changing world.

The U.S. GEOTRACES program is funded by the U.S. National Science Foundation.

GP15 blog posts written by Alex Fox unless otherwise stated.

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GEOTRACES GP15 is supported by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this material do not necessarily reflect the views of the National Science Foundation.

Loading up and shoving off

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The 277-foot R/V Roger Revelle is the home, laboratory and transportation for the 59 scientists and crew studying ocean chemistry between Alaska and Tahiti.Here the Revelle sits in port at Smith Cove in Seattle, WA, while all was made ready for more than two months at sea. Photo: Alex Fox

At noon on September 18 the Research Vessel Roger Revelle set sail, and a journey of more than 5,000 miles began. Over the prior four days, more than 50 scientists and crew worked together to pack the nearly 300-foot Revelle to the gills.

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Crates upon crates waiting to be loaded on the R/V Roger Revelle in Seattle’s Smith Cove. Photo: Alex Fox

Organizing chaos

Cranes, forklifts and muscle lifted 88 full pallets of equipment on board for the 67-day oceanographic expedition from Alaska to Tahiti. Three shipping containers converted into laboratories now sit where there was once empty deck. Down below, narrow hallways and steep staircases lead to a hive of workstations devoted to different types of analysis. The scientific equipment on board supports 26 separate research projects from 25 of the nation’s leading research institutions.

Scientists and crew will lower many of the key instruments on board to the bottom of the ocean. On their way back up, some instruments collect seawater while others measure things like the water’s temperature and salinity. To manage these deep sea dunks, the Revelle is packing roughly 95,000 feet of cable attached to four huge winches—more than three times the height of Mount Everest (29,029 feet).

Some samples hauled up from the depths need lab space free of potential contaminants to be accurately measured. Creating such a space on a ship that is decidedly not free of contaminants requires a lot of plastic, tape and an array of air filters.

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One of the doors to the clean room in the main lab flaps open, and a transparent plastic window adds a homey touch to the sterile environment. Photo: Alex Fox

Scientists build these clean rooms, called “bubbles,” with walls of plastic that balloon out with the clean air the filters are pumping in. That air escapes through the door flaps of the bubble and the slight pressure of leaking air helps keep wayward gunk from getting in.

On such a long expedition and with so many people on board, everyday details like food are writ large.

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A handful of the 12 pallets of food the ship’s crane hoisted on board. To get the boxes of food down to the ship’s fridge, freezer and storage rooms all hands on deck formed a human conveyor belt. Photo: Alex Fox

Twelve pallets stacked six-feet high took more than three hours and all hands on deck to bring down to the ship’s refrigerator, freezer and dry food storage rooms. The cost of all that food topped $43,000. That total may seem astronomical, but, spread across 59 people and 67 days, each person’s daily share of food is $10.87.

Leaving port

At 11:30 a.m., over the loudspeaker the captain called out, “All ashore who’s going ashore!”A flurry of trash bags and cardboard boxes flew over the ship’s rails into a nearby dumpster and a few stragglers made their escapes.

Then one of the ship’s cranes lifted the gangway plank leading from dry land to the floating Revelle. The 20-odd-feet of steel rose lightly off its hinge and pirouetted into parallel with the ship’s side where it was secured in place.

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Seattle fades into the distance as the R/V Roger Revelle motors full steam ahead at 12 knots on September 18. Photo: Alex Fox

The 59 people on board prepared for the next month living and working together to better understand the Pacific Ocean, and thick ropes were untied and thrown back to the Revelle. After days of intermittent rain in Seattle, the noonday sun burned through to blue sky and lit the way out of Puget Sound.

GP15 blog posts written by Alex Fox unless otherwise stated.

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GEOTRACES GP15 is supported by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this material do not necessarily reflect the views of the National Science Foundation.

Packing time!

One of the most important parts of going to sea is planning. That includes what we will do at sea to achieve our science objectives, but also what we need to pack and take with us. Once we depart, there is no turning back!

Across the country, participating laboratories have packed up and shipped all of the research supplies that will be needed for the cruise. These items are now en route to Seattle for mobilization, starting on September 14.

Mobilization is the period of time we get to load and set up the ship according to our needs for this cruise. We will be posting updates during mobilization later this week. But for now, we wanted just to post a few pictures of shipments heading out to Seattle for the cruise.

Post by Co-chief Scientist Karen Casciotti.

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GEOTRACES GP15 is supported by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this material do not necessarily reflect the views of the National Science Foundation.

The Journey Begins (almost)

The GEOTRACES GP15 oceanographic research cruise will set sail September 18, 2018 from Seattle, Washington. Our expedition will end in Tahiti on November 24, 2018. Follow us here, as well as on Facebook (@followGP15) and Twitter (@followGP15).

The track our cruise will follow is shown on the map below!cruise track 30July2018

Post by Co-chief Scientist Karen Casciotti.

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GEOTRACES GP15 is supported by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this material do not necessarily reflect the views of the National Science Foundation.