Concern about ocean iron levels: implications for reduced ocean uptake of CO2

Parliamentary Yearbook examines an article which reports large regional variations in the presence of iron in our oceans.  This is important because ocean iron plays a vital role in determining the rate at which oceans absorb atmospheric carbon dioxide. This absorption - and its rate - are critically important to the rate and  extent  of global warming and so affects the prospects for human survival.

The burning of coal, oil and methane gas provides the main source of energy in modern society.  However, this process releases carbon dioxide as a by-product. Years of burning these fossil fuels have significantly increased carbon dioxide levels in the Earth’s atmosphere. The atmospheric carbon dioxide level has become so great that it acts like a blanket. An overwhelming majority of the world’s scientists agree that this is causing the Earth to warm and driving climate change.

The oceans play an important role in moderating the impact of global warming.  According to the National Oceanography Centre, the oceans absorb one quarter of all the carbon dioxide emitted into the atmosphere.  Once dissolved into the ocean, it is estimated that this absorbed human waste product will stay there for more than 500 years on average. So, as with the rain forests, the oceans form a sink absorbing pollution. As is now well understood, pollution of the common environment is not a cost of production which is computed by our market-based costing system and is instead an “externality” assigned to populations. In this way, market accounting can continue to respect and privilege the paramount interests of short-term economic profit and rent on which – with the best will in the world - our present form of life unsustainably depends.

One way the ocean takes up carbon dioxide is through the process of photosynthesis occurring in microscopic plant-like organisms called phytoplankton. These single cell plants use energy from the sun to convert carbon dioxide and nutrients into complex organic compounds which form new plant material. During the process, phytoplankton also release oxygen into the water.  It is a vitally important process. Half of the world’s oxygen is produced via phytoplankton photosynthesis.

However, photosynthesis is limited by a lack of iron. Dr Will Homoky, from the University of Southampton, has recently described the importance of iron in this process: “Iron acts like a giant lever on marine life, storing carbon.  It switches on growth of microscopic marine plants, which extract carbon dioxide from our atmosphere and lock it away in the ocean.”

‘Continental margins’ are a major source of dissolved iron entering the oceans.  This is the zone of the ocean floor that separates the thin oceanic crust - composed of rocks rich in iron and magnesium - from thick continental crust (made of the igneous, sedimentary and metamorphic rock that forms continents). 

To date, iron measurements have been taken from a limited number of global regions. However, a new study, which focused on a region in Atlantic waters off the coast of South Africa, has identified that the amount of dissolved iron released into the oceans varies in ways previously not understood, by up to 10,000 times. 

The study, led by researchers based at the National Oceanography Centre in Southampton, reports that the amount of iron leaking from continental margin sediments varies significantly between regions.  Alarmingly, the study identified substantially smaller levels of iron being released into the seawater than measured anywhere before.

The findings are important because they have implications for models of climate change and could alter predictions for the future of climate change in the most unwelcome way.

The scientific community continues to issue its warnings. But to largely deaf ears in business, government and media, for reasons that are deep and not easily changed.

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