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A Worrying Prognosis for Ocean Health

By Alex Hammond

Funded by the European Union (EU) and implemented by Mercator Ocean International, a center for global ocean analysis and forecasting, Copernicus Marine Environment Monitoring Service (CMEMS) is one of six services delivered by the EU Copernicus Earth Observation Programme (CEOP). Dedicated to ocean observation and monitoring, it provides regular and systematic core reference information on the state of the physical oceans and European regional seas.

The continued findings of this ocean monitoring program are published annually in the CMEMS Ocean State Report, which charts physical changes in the world’s ocean over several decades. The second edition of the report focuses on the more pronounced variations recorded in 2016 and arrives in the wake of a number of record-breaking extreme weather events across Europe.

The report is a summation of the work of more than 100 scientific experts from more than 30 European research centers, which draws upon empirical data gathered from both satellite and in-situ measurements, as well as numerical models carried out under CEOP. Its overarching aim is to collate, analyze and interpret this unique corpus of data, describing both natural oceanic variation, as well as consequential changes resulting from climate change.

The report draws particular attention to the rising heat content of the global oceans and European seas. Corroborating previous studies, the research indicates that the volume of sea ice in the Arctic is declining by an estimated 15.4 percent, and sea ice extent is receding by 6.2 percent per decade. It reveals a simultaneous decline in the volume and extent of Antarctic sea ice in the closing stages of 2016—an event unprecedented in the history of satellite observation of the region.

This is startling news given that, until now, it was understood that Antarctic sea ice was slowly but steadily growing at a rate of 1.6 percent in extent and 8.8 percent in volume per decade. The triggers for this reversal are unclear; however, it has been hypothesized that it could be the consequence of a complex interplay of variations in ocean hydrography and air-sea interfaces, such as wind-driven processes.

The large variations in the Atlantic Meridional Overturning Circulation (AMOC), a sweeping ocean conveyor system that circulates water throughout the Atlantic, between 1993 to 2016 are also chronicled in detail. AMOC has weakened significantly since 2005; however, owing to historically high variability, researchers are still reluctant to declare this as an ongoing trend. The weakening of the AMOC has also been linked with a deceleration of the Gulf Stream over the past 25 years. This is of particular concern, given that the Gulf Stream affects sea levels and draws nutrients up from the ocean depths, both of which are crucial in sustaining marine ecosystems and fisheries worldwide.

The potential future consequences on marine ecosystems are further explored in the report’s documentation of oceanic carbon sequestration. The latest results illustrate that while carbon uptake by the world’s oceans was relatively stable during the 1990s, a sharp increase in CO2 sea-to-air exchange has been recorded since the early 2000s. Often referred to as climate change’s “evil twin,” this acidification of the oceans will have a devastating impact on biodiversity and knock-on effects on fisheries and aquaculture. When coupled with a weakened AMOC, this presents a significant threat to food security for millions of people worldwide.

While this article can only offer a snapshot of the 150-page report, it is clear that the extensive assortment of data collected and analyzed by CMEMS paints a bleak picture for ocean health in the coming century. To develop effective mitigation measures, it is vital we develop better sustainable and science-based reporting and management strategies. Achieving these requires long-term, continuous and state-of-the-art monitoring of the oceans on a variety of spatial scales.

The ongoing publication of the Ocean State Report will assist in this endeavor, as it presents great value as a reference document on ocean health and climate. It is designed to serve stakeholders across the commercial and scientific marine sectors, as well as to support major EU policies. In doing so, it helps businesses in the blue economy better understand and anticipate future changes in the environment in which they operate, while also informing and stimulating further multidisciplinary scientific research.

Furthermore, it will support national and regional authorities in preparing more effective and robust strategies for tackling the challenges of an ever-changing climate.

The Ocean State Report is an open-access publication issued as an annual special supplement in the Institute of Marine Engineering, Science and Technology (IMarEST) Journal of Operational Oceanography (JOO). To read the full report, visit tandfonline.com/tjoo.


Alex Hammond is the technical communications executive at the Institute of Marine Engineering, Science and Technology. He has a master’s degree in ecology from the University of Southampton in the U.K. Hammond has experience in science communications across the science and engineering domain, with particular experience in marine biology and issues relating to coral reef ecology.