Scientists from the Woods Hole Oceanographic Institution (WHOI) have conducted a new study to measure levels of carbon at various depths in the Arctic Ocean.
The study, recently published in the journal Biogeosciences, provides data that will help researchers better understand the Arctic Ocean’s carbon cycle—the pathway through which carbon enters and is used by the marine ecosystem. It will also offer an important point of reference for determining how those levels of carbon change over time, and how the ecosystem responds to rising global temperatures.
“Carbon is the currency of life. Where carbon is coming from, which organisms are using it, how they’re giving off carbon themselves—these things say a lot about how an ocean ecosystem works,” says David Griffith, the lead author on the study. “If warming temperatures perturb the Arctic Ocean, the way that carbon cycles through that system may change.”
Griffith’s team sampled suspended particles of organic matter, as well as organic carbon and carbon dioxide (CO2) dissolved into the surrounding water. This is the first time that researchers have focused broadly on measuring multiple types of carbon at the same time and place in the Arctic Ocean—due to its remote location and the challenges of operating in sea ice, few comprehensive carbon surveys had been conducted there before this study.
Griffith and his colleagues conducted their fieldwork in 2008 aboard the Canadian Coast Guard icebreaker Louis S. St. Laurent. At two different spots in the Canada Basin, an area northwest of the Canadian coast, they gathered samples from 24 depths ranging from the surface to the ocean floor 3800 meters (roughly 12,500 feet) below.
Collecting samples at those intervals was necessary, Griffith says, because the Arctic Ocean is separated into distinct layers, each with its own unique carbon characteristics. At the surface is a freshwater layer from river runoff and sea-ice melt. Below that is a layer of cold water from the Pacific, and below that is a warm, salty Atlantic layer. The deepest layer is slowly replaced by mixing with overlying Atlantic water.
Measuring the different amounts of carbon in each layer (and determining its source) is an essential step in understanding the flow of carbon through the marine ecosystem, says Griffith: “It’s kind of like understanding how freight and people move in a city. If you don’t know what’s coming in and out, it’s really hard to understand how the city works.”