New Discoveries Could Improve Climate Projections

USGS News Release, December 11, 2009

New discoveries about the deep ocean’s temperature variability and
circulation system could help improve projections of future climate
conditions.

The deep ocean is affected more by surface warming than previously thought,
and this understanding allows for more accurate predictions of factors such
as sea level rise and ice volume changes.

High ocean surface temperatures have also been found to result in a more
vigorous deep ocean circulation system. This increase results 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 deep ocean is relatively unexplored, and we need a true understanding
of its many complex processes,” said U.S. Geological Survey Director Marcia
McNutt. “An understanding of climate change and its impacts based on sound,
objective data is a keystone to the type of long-term strategies and
solutions that are being discussed now at the United Nations conference in
Copenhagen.”

USGS 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.

“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.

Read the full article, published <http://www.clim-past.net/5/769/2009/>  in
Climate of the Past.

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. Learn more
about PRISM research <http://geology.er.usgs.gov/eespteam/prism/index.html>