Scientists from the Woods Hole Oceanographic Institution (WHOI) have concluded a study to measure levels of carbon at various levels in the Arctic Ocean, providing a baseline for further understanding.
The study was recently published in the journal Biogeosciences. It provides data that will help researchers in the future as they try to better understand the Arctic Ocean’s carbon cycle.
“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 travelled aboard the Canadian Coast Guard icebreaker Louis S. St. Laurent to the Canada Basin in 2008 and gathered samples from 24 depths ranging from the surface to the ocean floor 2,800 metres below. They sampled suspended particles of organic matter as well as organic carbon and carbon dioxide dissolved into the surrounding water.
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.”
Griffith then turned their samples over to Ann McNichol, a WHOI senior researcher and staff chemist. At WHOI’s National Ocean Sciences Accelerator Mass Spectrometer Facility (NOSAMS), Ann tallied the number of carbon atoms in each specimen.
In addition to understanding the basic carbon cycle in the Arctic Ocean, Griffith’s team hopes that the results of this baseline study will help evaluate how Arctic Ocean carbon levels and global climate interact. Griffith says there are several ways this could happen.
As the Arctic gradually warms, it may cause a more intense precipitation cycle over northern Canada, Alaska, and Siberia, generating more rainfall each year. This in turn would cause more runoff from melting permafrost and eroded soil—both rich sources of organic carbon.
One possible outcome of that scenario could be an increase of carbon dioxide in the region. As bacteria in Arctic Ocean use the new influx of carbon as a food source, they may create CO2 as a byproduct. A second possibility, Griffith posits, is that warming temperatures and melting sea ice might boost the production of phytoplankton, tiny plant-like organisms that live near the ocean’s surface and thrive on carbon dioxide in the water. As those phytoplankton die (or are eaten by other organisms and released as waste), they would sink to the sea floor, causing the carbon in their bodies to be sequestered in thick sediments—effectively removing the increased carbon from the environment.
“Those are just a few aspects of what might happen. But for every one that we think about, there could be 10 others that drive the system in a different direction,” says Griffith. “We don’t yet have the kind of data to say anything definitive about how the Arctic would be affected by warming climate—but what we do have is a very important baseline of data to help evaluate changes that will happen in the future. Without that, you‘re unfortunately just guessing at how things change over time.”
Adapted from material provided by Woods Hole Oceanographic Institution (WHOI).