Ocean Carbon Sleuths

Wednesday, March 29, 2017

Scientists at UC Santa Barbara’s Earth Research Institute, led by oceanographer David Siegel, have taken on the challenge of quantifying present conditions in the ocean’s carbon cycle and developing tools to predict its future states. Knowledge obtained as a result of the project will provide a deeper understanding of how the ocean’s carbon-transport processes may affect climate change around the world.

“Predicting how the ocean’s carbon cycle changes in the future remains one of the greatest challenges in oceanography,” Siegel said.

To gain the knowledge and understanding they seek, the researchers have developed a plan that involves using a wide range of data-collection methods to inform a comprehensive understanding of how the world’s oceans process carbon. Called the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) Science Plan, the blueprint, which was written for NASA, will employ such methods as modeling, sampling, and remote sensing to get a deep understanding of how the ocean — the Earth’s most effective carbon sink — absorbs and stores carbon.

While the total amount of carbon found on Earth and in its atmosphere remains constant, the levels of carbon held in the air and the ocean, in rock, and in living organisms shifts continuously. Because of its depth and vastness, the ocean plays a major role in that constant, complex carbon flux. Some mechanisms dissolve carbon in surface waters, while others cause it to be absorbed in the process of photosynthesis. Organisms take up carbon as part of the shells or exoskeletons they form, and when they die, much of that material sinks to the sea bed, forming sediments and, eventually, rocks. A fraction of ocean carbon is also released back into the air when deep waters circulate upward and meet the warmer temperatures of the surface, causing evaporation.

Understanding this biological pump is critical, according to Siegel. Rising temperatures and changes in nutrient concentrations could, for instance, affect the ocean’s surface ecosystem and, hence, its ability to absorb and sequester carbon effectively, which would, in turn, influence carbon levels in the atmosphere.

The researchers are pursuing several types of data sets detailing the ecosystem characteristics of the ocean’s surface, such as water temperature, salinity, oxygen levels, and phytoplankton types, sizes, and productivity. That information can be used to create snapshots of the ocean’s biological pump, which can be used to understand how it functions as a complete global system. Further analysis will help scientists understand where carbon moves and how much of it gets converted into organic matter. According to Siegel, this would provide a better idea of how air-sea exchanges of carbon dioxide are affected and what happens to combusted fossil fuels.

Given increasing levels of CO2 in the atmosphere and the oceans and the continuing increase in global carbon emissions, detailed knowledge of how the planet's largest carbon sink functions and interacts with other planetary systems cannot come too soon.

UC Santa Barbara beach at sunset