Ocean warming has doubled in recent decadesAmy Walsh (Author) Published Date : Jan 19, 2016 20:11 IST
Researchers have found that man-made heat has raised ocean temperatures, twice of what was experienced 150 years ago.
Since the 1990s, the total amount of heat content change in the oceans is twice that of what we d seen up until that point in the past 150 years, said Chris Forest, a Penn State meteorology professor and associate in the university s Earth and Environmental Systems Institute.
Formal detection and attribution studies have used observations and climate models to identify an anthropogenic warming signature in the upper (0 700 m) ocean.
Recently, as a result of the so-called surface warming hiatus, there has been considerable interest in global ocean heat content (OHC) changes in the deeper ocean, including natural and anthropogenically forced changes identified in observational modeling and data re-analysis studies.
Here, researchers examined OHC changes in the context of the Earth s global energy budget since early in the industrial era (circa 1865 2015) for a range of depths. They relied on OHC change estimates from a diverse collection of measurement systems, including data from the nineteenth-century Challenger expedition, a multi-decadal record of ship-based in situ mostly upper-ocean measurements, the more recent near-global Argo floats profiling to intermediate (2,000 m) depths, and full-depth repeated transoceanic sections. Researchers report this in the journal Nature Climate Change.
We show that the multi-model mean constructed from the current generation of historically forced climate models is consistent with the OHC changes from this diverse collection of observational systems. The model-based analysis suggests that nearly half of the industrial-era increases in global OHC have occurred in recent decades, with over a third of the accumulated heat occurring below 700 m and steadily rising.
Analyzing changes in the deepest parts of the ocean has been more difficult. There is less historical data to draw on, but available information does show warming, even in the bottom layers of the ocean in recent decades. Scientists said it is vital to continue studying this and other ocean depths in the coming decades.
People need to understand that the length of the record is critical to making these statements, Forest said. Maintaining good networks of data collection around the globe, in the ocean at all levels is necessary for us to continue to learn how systems are responding. We need to continue getting this data and make sure we know how the ocean is responding over the next 20 years and beyond.
Ocean warming has doubled in recent decades