NOC study shows sea level continues to rise

Warming of the ocean and the melting of the glaciers and ice sheets

For 150 million people living in coastal areas around the world, rising sea level will become a genuine threat according to a new international study which found convincing evidence the sea level has been rising over the past 200 years – and continues to rise.

Warming of the ocean and the melting of the glaciers and ice sheets are the cause of the sea level rise, said Dr Svetlana Jevrejeva from the UK’s National Oceanography Centre (NOC), who co-authored the scientific research paper.

“There is a huge inertia in the climate system, so even if we stop the warming of our planet now – if we stop emitting greenhouse gases into the atmosphere today – the global sea level will continue to rise for the next few hundred years.

“We are facing a colossal challenge – to deal with carbon emissions as soon as possible,” said Dr Jevrejeva.

With about 150 million people living within one metre of high tide globally, sea level rise is one of the most damaging aspects of a warming climate. The vulnerability of extensively populated coastal areas, the threats to infrastructure, and population migration are major concerns for society, Dr Jevrejeva said.

“Fifteen of the world’s 20 megacities, with populations of more than 10 million, are sensitive to sea level rise and increased coastal storm surges.

“Soon we will have to make very hard decisions in the UK and globally: which coastal area is going to be protected and which could be abandoned? It means that as a civilization we are not able to protect some of our cultural heritage, unique beaches and cliffs.”

The scientific paper called Trends and acceleration in global and regional sea levels since 1807‘ has been published in the Global and Planetary Change journal. Co-authors with Dr Jevrejeva are JC Moore from the Beijing Normal University in China, A Grinsted from the University of Copenhagen in Denmark, AP Matthews from NOC and G Spada from the Dipartimento di Scienze di Base e Fondamenti, Università degli Studi “Carlo Bo” in Urbino, Italy.

The study looked at global sea level reconstruction based on 1,277 tide gauge records dating from 1807 to 2010. Tide gauge observations suggest that sea level rose by 6 cm during the nineteenth century, 19 cm during the twentieth century, and the sea level has continued to rise this century.

Sea level is the integrated response of the climate system to changes in the atmosphere, cryosphere and ocean. It could be considered as an indicator of the health of our planet. Over the past 2000 years, sea level was almost stable but since the 1800s it has started to rise.

The ocean has stored over 90 percent of the energy in the climate system, resulting in ocean thermal expansion and hence sea level rise. In addition, the warming ocean is playing an important role in supplying the heat to the Polar Regions, contributing to the ice loss from ice sheets.

To understand the past sea level rise the researchers used the historical tide gauge records collected by the Permanent Service for Mean Sea Level (PSMSL), which were key assets. Established in 1933, the PSMSL has been responsible for the collection, publication, analysis and interpretation of sea level data from the global network of tide gauges. It is based in Liverpool at the National Oceanography Centre. All of PSMSL’s data are available from the web page http://www.psmsl.org/data/.

Dr Jevrejeva said: “Credit goes to all tide gauge operators, local authorities, national data centres and individuals for making these data available for the PSMSL. Scientists, including myself, working for PSMSL take care of these data and make them available for the wider scientific community. PSMSL data have been employed intensively in studies such as those of the Intergovernmental Panel on Climate Change (IPCC).

Dr Jevrejeva is currently working on future sea level projections in coastal areas globally for the EU project RISES-AM. In that project, the team is providing estimates of sea level rise by 2100 for the high-end scenarios, which is where the temperature rises more than 2⁰ Celsius.

Source:National Oceanography Centre