Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Climate Change: Ocean Warming Underestimated

26.01.2016

To date, research on the effects of climate change has underestimated the contribution of seawater expansion to sea level rise due to warming of the oceans. A team of researchers at the University of Bonn has now investigated, using satellite data, that this effect was almost twice as large over the past twelve years than previously assumed. That may result in, for example, significantly increased risks of storm surges. The scientists are presenting their findings in the renowned scientific journal “Proceedings of the National Academy of Sciences of the United States of America” (PNAS).

In principle, water in the oceans acts like a mercury thermometer: when the temperature goes up, the liquid expands and climbs up the little tube. Since the world’s oceans are similarly locked in between the continents, their levels also rise when they heat up due to rising temperatures.


Dr.-Ing. Roelof Rietbroek from the Institute for Geodesy and Geoinformation at the University of Bonn, with a global illustration of the rise in sea levels on his computer monitor.

© Photo: Johannes Seiler/Uni Bonn

“In the deeper parts of the ocean, even a small amount of warming is enough to create a significant rise in sea level,” says Dr.-Ing. Roelof Rietbroek from the Institute of Geodesy and Geoinformation at the University of Bonn. An increase of several millimeters a year, he says, is not rare in deep-sea zones.

“To date, we have underestimated how much the heat-related expansion of the water mass in the oceans contributes to a global rise in sea level,” says Dr. Jürgen Kusche, Professor of Astronomical, Physical and Mathematical Geodesy at the University of Bonn.

Together with researchers at the Deutsches GeoForschungsZentrum (GFZ) in Potsdam and the Alfred Wegener Institute (AWI) in Bremerhaven, the geodesists used gravity field data from the GRACE satellites and sea-level measurements from the altimeters on Jason-1 and Jason-2 to calculate how much sea levels had risen, both due to warming-related expansion of the water and due to the increase of ocean mass from 2002 to 2014.

Effect is twice as large as the melting ice masses in Greenland

Until now, it was assumed that sea levels rose an average of 0.7 to 1.0 millimeters a year due to this “thermometer effect.” According to the new calculations, however, the ocean’s expansion contributed with about 1.4 millimeters a year – in other words, almost twice as much as previously assumed. “This height difference corresponds to roughly twice the volume from the melting ice sheets in Greenland,” says Dr. Rietbroek.

In addition, the sea-level rise varies strongly due to volume expansion in various ocean regions along with other effects. According to the research team’s calculations, the Philippines hold the record with about 15 millimeters a year, while the levels are largely stable on the West Coast of the United States – because there is hardly any ocean warming in that region.

Risk of storm surges could increase significantly

The main areas threatened by rising sea levels are coastal settlements, where regional changes can play a greater role than the global increase. “No country will raise its levees because of a couple of millimeters,” says Dr. Rietbroek. “But these small amounts add up to several centimeters within decades. Under such conditions, the likelihood of a destructive storm surge could increase dramatically.” From the perspective of the research team, it is thus worth keeping an eye on the expansion-related sea-level rise in the world’s oceans in light of climate change. Little measurement data is available, they say, to show how much the oceans are warming up and expanding at depths of thousands of meters in conjunction with rising global air temperatures.

“Up to now, the physical expansion processes in the deep sea have been considered only to a limited extent,” says the geodesy researcher from the University of Bonn. However, he says, they play a key role in estimating the climate effects. Therefore it would be highly interesting to observe future heat-related expansion of the world’s oceans, using new satellite missions, and to reinterpret measurement data from the past. A longer observation period will help show what proportion of the rise in sea level is due to human activity, and what proportion is due to natural causes. Dr. Rietbroek: “In addition, the estimated trend in sea level is much less affected by natural fluctuations compared to the observed trend in global temperatures, so it is a more reliable indicator of climate change.”

Publication: Revisiting the Contemporary Sea Level Budget on Global and Regional Scales, Proceedings of the National Academy of Sciences of the United States of America (PNAS), DOI: 10.1073/pnas.1519132113

Media contact:

Dr.-Ing. Roelof Rietbroek
Institute of Geodesy and Geoinformation
University of Bonn
Tel. ++49-228-733577
Email: roelof@geod.uni-bonn.de
Twitter: @r_rietje

Weitere Informationen:

http://store.pangaea.de/Publications/RietbroekR-etal_2015/Sealevel_pnasRietbroek... Google Earth can also be used to visualize some of the results available here

Johannes Seiler | idw - Informationsdienst Wissenschaft
Further information:
http://www.uni-bonn.de/

Further reports about: Climate Friedrich-Wilhelms-Universität levels oceans sea level

More articles from Earth Sciences:

nachricht Climate satellite: Tracking methane with robust laser technology
22.06.2017 | Fraunhofer-Gesellschaft

nachricht How reliable are shells as climate archives?
21.06.2017 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Study shines light on brain cells that coordinate movement

26.06.2017 | Life Sciences

Smooth propagation of spin waves using gold

26.06.2017 | Physics and Astronomy

Switchable DNA mini-machines store information

26.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>