Ocean Temperature Finding May Improve Projections, USGS Says

U.S. Geological Survey scientists created the first ever 3-D reconstruction of an ocean during a past warm period, focusing on the mid-Pliocene warm period 3.3 to 3 million years ago. They found that the deep ocean is affected more by surface warming than previously thought, which could allow for more accurate predictions of sea level rise and ice volume changes attributed to global climate change. High ocean surface temperatures have been found to result in a more vigorous deep ocean circulation system, resulting in a faster transport of large quantities of warm water, with possible impacts including reduction of sea ice extent and overall warming of the Arctic.

The study was published "Pliocene three-dimensional global ocean temperature reconstruction" in Climate of the Past.

"Our findings are significant because they improve our previous understanding that the deep ocean stayed at relatively constant, cold temperatures and that the deep ocean circulation system would slow down as surface temperatures increased," said USGS scientist Harry Dowsett. "By looking at conditions in the past, we acquire real data that allow us to see the global climate system as it actually functioned."

"The average temperature of the entire ocean during the mid-Pliocene was approximately one degree warmer than current conditions, showing that warming wasn’t just at the surface but occurred at all depths" said USGS scientist Marci Robinson. "Temperatures were determined by analyzing marine plankton fossils, which are organisms that inhabited the water’s surface, as well as fossils of bottom-dwelling organisms, known as ostracodes."

Global average surface temperatures during the mid-Pliocene were about 3°C (5.5°F) greater than today and within the range projected for the 21st century by the Intergovernmental Panel on Climate Change. Therefore it may be one of the closest analogs in helping to understand Earth’s current and future conditions. USGS research on the mid-Pliocene is also the most comprehensive global reconstruction for any warm period.

The USGS led this research through the Pliocene Research, Interpretation and Synoptic Mapping group. The primary collaborators in PRISM are Columbia University, Brown University, University of Leeds, University of Bristol, the British Geological Survey and the British Antarctic Survey.

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