What is GEOTRACES?
GEOTRACES is a global effort to better understand the world’s oceans through chemistry and oceanography. The goal of GEOTRACES is to figure out the distributions of various elements and their isotopes in the ocean. Many “trace elements” (which are by definition scarce) are also important for marine life. For instance, phytoplankton, the tiny plants at the base of many ocean food webs, need iron to grow. Everything from tiny fish to giant whales eat phytoplankton, in the population of marine ecosystems and carbon dioxide uptake by the oceans. Until quite recently, these elements could not be measured at a global scale. Understanding the distributions of these elements and isotopes will increase the understanding of processes that shape their distributions and also the processes that depend on these elements.
What is GP15?
This expedition, code named “GP15,” was an important U.S. GEOTRACES mission. The Research Vessel Roger Revelle carried 59 scientists and crew through the Pacific Ocean along 152° W between Alaska and Tahiti (see map below). This path allowed us to examine the influence of strong margin fluxes, atmospheric dust deposition, and the distal ends of hydrothermal plumes from the Juan de Fuca Ridge and East Pacific Rise as well as oxygen minimum zones, equatorial upwelling, and some of the lowest-nutrient waters in the world’s oceans in the 
South Pacific gyre at 20°S. It was the first meridional section of the U.S. GEOTRACES program, and indeed, this transect allowed us to explore virtually all of the processes and fluxes known to introduce trace elements to the ocean.
This project also provides baseline measurements of trace elements in the Clarion-Clipperton fracture zone (~7.5°N-17°N, ~155°W-115°W) where large-scale deep sea mining is planned. Environmental impact assessments are underway in partnership with the mining industry, but the effect of mining activities on trace elements in the water column is one that could be uniquely assessed by the GEOTRACES community.
This expedition supported a large variety of individual science projects to study the chemical and biological interactions of trace elements, with some research being conducted on board the ship, and additional research at participating academic laboratories across the country (please see our collaborators page).
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You can find an archive of blog posts created during this expedition here.
Blog posts created or edited by Alex Fox.
Follow GEOTRACES GP15 on WordPress.com
Funding for this research is provided by NSF Chemical Oceanography.
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.
GEOTRACES GP15 