An uncertain future for the Arctic ocean

© F. Bernard / Tara Expeditions Foundation

At the beginning of December 2018, the National Oceanic and Atmospheric Administration (NOAA) stated in its annual report that 2018 has been the second-warmest year recorded in the Arctic Ocean since 1900. Further evidence that global warming is accelerating. Polar regions are particularly impacted by the changes related to anthropic activities.

An ecosystem facing profound and irreversible changes

High temperature records are increasing. This is only one of many clues illustrating how our behaviors impact the planet. The Arctic Ocean is often presented by scientists as one of the ecosystems the most affected by climate disruptions. As a result, the question of how this ecosystem will evolve in the years to come is even more pressing than for other ecosystems. Scientists have recently confirmed that the Arctic Ocean is warming up twice as fast as the rest of the planet. Over the course of 2018, the air temperature anomaly rose by 1.7°C on average.

Ice sheets are getting thinner and receding, thus increasing the surface area of open water, less efficient in reflecting solar radiation. More heat is absorbed which amplifies global warming. According to the National Snow and Ice Data Center, the ice cover in the Arctic Ocean in November decreased from 11.5 million square kilometers in 1978 to 9.8 in 2018, i.e. a decline of 15%. In November 2016 – the warmest year on record – the ice cover was particularly low: 8.6 million square kilometers. Regardless of the period of the year and region studied, the Arctic ice extent decreases. Moreover, ocean currents and circulation change, water warms up and acidifies, and species migrate or disappear. The list of environmental impacts goes on and on.

© National snow and ice data center
Average monthly ice cover in the Arctic Ocean © National Snow and Ice Data Center
 

The marine ecosystems of this polar region are directly affected by all these disturbances. Impacts on plankton – first link in the food chain – spread to the entire food chain, up to top predators. As a result of global warming, some species migrate northward, possibly distressing the ecosystem’s initial organization. Within a few years, when maritime transport develops in the Arctic Ocean, invasive species, transported by vessels, will also risk impacts.

Understanding how the Arctic ecosystem functions: an emergency

To describe the situation in the Arctic Ocean, scientists often speak of an upcoming “changeover”, a point of no return beyond which profound and irreversible changes are to be expected. We need to predict and define this changeover as best as we can to anticipate the inevitable consequences of the ocean disruptions, both in terms of organization of the Arctic Ocean ecosystem and marine resources.

Aware of the specific challenges revolving around the Arctic Ocean, the Tara Expeditions Foundation has been studying for a long time the issue facing this ecosystem and its microscopic organisms. We must remember that planktonic species play a fundamental role in the chemical composition of Earth’s atmosphere and climate change. Since the entire food chain depends on these organisms, they are, in many ways, a central element for the whole planet. Many oceanographers with complementary skills came together during the Tara Oceans Polar Circle expedition to collect a very large amount of biological and environmental data with the purpose of untangling the complexity of the Arctic planktonic ecosystem.

C.Sardet/CNRS/Tara Oceans Polar Circle
© C.Sardet/CNRS/Tara Oceans Polar Circle

The lab work is still in progress and requires more time, but once completed, scientists will be able to explain how plankton populations evolve and organize depending on temperature, oxygen and pH conditions, and how the upcoming changes will impact their structure.

Ocean species in general, and plankton in particular, are still poorly known. Scientists estimate that the vast majority is still unknown. The data collected aboard the schooner Tara will therefore allow us to update the catalog of ocean plankton diversity, offering a high discovery potential for mankind and its future.

 

Margaux Gaubert

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