Oceans: The Largest Active Carbon Reservoir

From global warming to rising sea levels, CO2 emissions have severely impacted many aspects of our climate. But the effects of CO2 would be a lot worse if it weren’t for the oceans. The oceans are the world’s largest active carbon reservoir, absorbing about a quarter of human CO2 emissions to the atmosphere. Ocean circulation and biology help transport carbon down, away from the atmosphere, and into the deep waters of the interior ocean.

But uptake of this extra CO2 is also causing the seawater to become more acidic at a faster rate, which adds extra stress to marine organisms already struggling to adapt to pollution and the changing climate. The ‘ocean acidification’ also means that the carbon storage capacity of seawater is declining and they are less able to mitigate future increases in atmospheric CO2. In order to predict how much CO2 remains in the atmosphere, researchers are trying to figure out how much carbon the ocean can continue to absorb.

Matthew Humphreys, a tenure track scientist at the Royal Netherlands Institute for Sea Research (NIOZ), is one of the researchers studying how the oceans respond to CO2 emissions. Matthew is part of a project focusing on carbon absorption in the Dutch sector of the North Sea. This is an extremely productive and commercially important area filled with fisheries and shellfish aquaculture sites--which are very vulnerable to changing climate, ocean acidification, and changes in CO2 levels. Every month, the Dutch Ministry of Infrastructure and Water Management (Rijkswaterstaat) collects samples of sea water from the area which Matthew uses to observe the seasonal changes in pH and carbon levels to try and determine long term trends. 

“The seasonal cycle is changing and we’re starting to see a bigger range of seasonal extremes in pH,” says Matthew. “It can cause problems for the organisms in the water if the carbon levels or pH change too much. You're exposing them to a tougher range of chemical conditions that they've got to adapt to. I'm trying to identify what's driving those changes, with the ultimate goal of being able to predict them better into the future.”

It is important that Matthew has access to the oceans to be able to do this work. Fortunately, NIOZ serves as national marine research facilitator for the scientific community in the Netherlands, so it has its own fleet of three research vessels. Just a month after starting his position, Matthew was already on a research cruise to the Caribbean on the Pelagia, NIOZ’s open ocean vessel. He was invited on board by another NIOZ scientist who wanted him to do some carbon dioxide work. Matthew was excited by the opportunity to get to know other colleagues at the institute and start working at sea. “I was in a very theoretical position before, doing a lot of computer work,” he says. “NIOZ has all these great lab facilities and the ships, which actually give me a lot of opportunities to get back to the ocean and do oceanography.”

In addition to the fleet and lab facilities, NIOZ also has fantastic technicians. There are three technicians who are dedicated to running the nutrient and carbonate chemistry equipment, something Matthew describes as “unprecedented” in his experience. The technicians help run samples, prepare for research cruises, and train PhD students. “They’re just a really great resource,” Matthew says.

He is also very complimentary of the NIOZ community and working atmosphere. Everyone at the institute takes a coffee break together at 10 and then stops for lunch at 12 to eat together in the canteen. “I came from a place where everyone ate lunch at their desks a lot of the time and wouldn't really stop working, so NIOZ is a nice change. And I've actually started working on new collaborations with some people in different fields that I met during the coffee breaks that probably wouldn't have come up otherwise,” says Matthew.

Like many NIOZ researchers, Matthew lives in the town of Den Helder which is an hour from Amsterdam by train and 20 minutes from NIOZ by ferry. “Taking the ferry to work every day is actually a really nice way to start your day at an oceanography institute. It does feel like you're doing it properly,” Matthew points out. “It’s been an easy transition to NIOZ and Den Helder. I’m really happy here.”