Chemical oceanography is the study of the pathways that chemical species follow on their transit through the oceans. Chemical oceanographers examine vast ranges of time and space scales...
- From molecular level to global in space
- From fractions of a second to billions of years in time
Besides addressing purely geochemical issues, chemical oceanographers work at the boundaries between chemistry and biology, geology and physics. There they apply their efforts to a broad spectrum of interdisciplinary challenges.
Human activities, such as fossil fuel combustion, biomass burning, and agriculture, release large amounts of carbon dioxide and other gases that influence climate into the atmosphere. As the atmospheric carbon dioxide level rises, both scientific and societal concerns grow over potential greenhouse warming and climate change. An important fraction of the carbon dioxide released into the atmosphere by human activities ends up in the ocean; without the oceans, atmospheric carbon dioxide levels would be even higher than they are today. Much research in chemical oceanography focuses on quantifying the ocean's rate of uptake of carbon dioxide and understanding the biological pump by which the carbon dioxide that enters the surface ocean is transferred to deep waters and sediments, to be sequestered from the atmosphere for millennia.
Some focal points of current research at WHOI and MIT are:
- Applying new physical and chemical measurements to the study of the air-sea boundary layer.
The result? Direct gas exchange estimates and new information on boundary layer properties that can be used by modelers to apply satellite-based measurements to the determination of ocean-wide air-sea gas exchange.
- Developing chemical and molecular techniques for understanding the controls on the photosynthetic activities of organisms living in the surface ocean.
These developments are coupled to the continual improvement of instruments that, when mounted on floating buoys, can make continuous, at-sea measurements.
- Improving and deploying instruments to measure the rain of particles from the surface to the deep ocean and to understand the processes that alter the particles during their transit.
These efforts have led to improvements in sediment traps so they can capture representative samples of falling particles and to the development of in situ pumps to capture suspended particles.
- Incorporating new chemical sensors and new technologies into instruments designed to sample marine sediments and to measure the composition of the waters contained in them.
These developments are driven by an increasing recognition that sampling of sedimentary pore waters must be carried out in situ, on the sea floor—a requirement that challenges even the most innovative engineers.
- Understanding past, abrupt climate change can provide key insights into what may await us in the future.
Scientists at WHOI and MIT are developing tools for investigating past changes. Organic geochemists exploit knowledge of specific biochemical pathways and advances in analytical instrumentation to develop chemical and isotopic tracers of biogeochemical processes and seawater characteristics that have changed over time.
New developments in mass spectrometry are allowing more types of measurements on more types of samples than ever before, thereby helping investigators to continually broaden the scope of the study of past climate change.
- Tracing the pathways of anthropogenic emissions through the oceans (for example, bomb fallout tritium,carbon-14, and plutonium, Chernobyl and Fukushima radionuclides, anthropogenic lead and mercury, and organic pollutants such as PAH (polycyclic aromatic hydrocarbons)
As well as establishing the anthropogenic footprint upon the ocean, these studies help us to estimate transport times and mechanisms that move these substances through the ocean.
Connecting earth to sea
The organic and inorganic chemistry of seawater and marine sediments cannot be isolated from processes on land and in the earth's crust beneath the ocean. As a result, there is a strong solid earth geochemistry component to research at WHOI and MIT.
Extensive sampling, both on land and beneath the sea, sophisticated laboratory experiments at in situ temperatures and pressures, and thermodynamic modeling are some of the techniques that are coupled with the wide array of state-of-the-art analytical instruments available at WHOI for the study of solid earth processes.
Studies are underway to understand the ways in which continental weathering influence the composition of river water and seawater, to evaluate the effect of undersea hydrothermal activity on the composition of seawater and oceanic crust, and to reconstruct paleo-environmental conditions on land and in the sea.
Sampling and measuring
All work in chemical oceanography at MIT and WHOI is driven by the goals of collecting the best samples and making the best measurements possible, using and sometimes leading the development of the latest sampling and analytical tools.
To achieve these goals, you might find yourself...
- Elbow-deep in a nitrogen-filled glove bag, sampling sediments for organic or inorganic contaminants
- Wading in coastal waters to measure exchanges between land and ocean via groundwater flow
- Deploying instruments and making measurements on a rolling ship at sea
- Exploring hydrothermal vents in a submersible
- Sampling rocks in Antarctica, armed with a hammer and a backpack
The range of research opportunities open to you in chemical oceanography in the WHOI/MIT Joint Program is limited only by your imagination.