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Photo of assorted reef fish at Shark Reef off Beqa Island.

Assorted reef fish at Shark Reef off Beqa Island.

Photograph by Mattias Klum, National Geographic

Dan Vergano

National Geographic

Published October 31, 2013

The ocean depths may store more heat from global warming than suspected, suggests a 10,000-year record of past ocean temperatures measured in Indonesian seafloor cores.

At the same time, since 1950 Pacific Ocean waters have been warming at a rate 15 times faster than the rest of the seafloor, as reported in the journal Science.

"Under normal, natural conditions the oceans are a buffer for temperature changes in the atmosphere," says study lead author Yair Rosenthal of Rutgers University in New Jersey. "But right now, we are completely out of equilibrium." (See "What is Global Warming?")

Because the ocean depths are thought to absorb about 90 percent of the excess heat seen from global warming, increased attention has turned to their heat-absorbing capabilities in recent years.

Much of the roughly seven inches (18 centimeters) of average sea-level rise seen globally in the last century stems from "thermal expansion" of the oceans as they absorb heat. (See video: "A Way Forward: Facing Climate Change.")

The effect is expected to add almost two feet (61 centimeters) of sea-level rise, on average, to coasts worldwide in this century, leaving aside the effects of melting glaciers.

Seafloor Secrets

In the study, Rosenthal and his colleagues analyzed tiny, shelled creatures called foraminifera that pile up on the ocean floor and have preserved a record of past seawater temperatures from the last 10,000 years. (See also "Global Warming.")

The ratio of magnesium to calcium in the shells of the tiny single-celled creatures indicates the ocean temperatures at their time of formation. So the team could look at changes in this ratio to see shifts in ocean temperatures over time.

The scientists looked at two seafloor records from Indonesian water at depths of 1,480 to 3,018 feet (455 to 920 meters). The sites were selected because they are seen as representative of places where Pacific Ocean waters have mixed for millennia.

The study improves on recent work on past ocean temperatures, chiefly because it is looking at multiple sites from multiple depths, says paleoclimate expert David Anderson of the National Oceanic and Atmospheric Administration's National Climatic Data Center, located in Boulder, Colorado.

"Any story that can tell us how the upper 1,000 meters [of the ocean] warms and cools as the Earth's energy balance changes is of interest," says Anderson.

Ocean Thermometer

Overall, the ancient shells tell a story of long-term cooling of ocean waters, a drop ranging from 1.5 to 2.2 degrees Celsius (2.7 to 3.8 degrees Fahrenheit) across the depth, starting from roughly 7,000 years ago until the Middle Ages.

The records also discern a bump in temperatures during a warm period around the year 1200, followed by a drop during the Little Ice Age that stretched from 1550 to 1850.

"What we see is that it takes decades for the ocean to absorb changes in surface temperatures," Rosenthal says. "Clearly there is warming going on now, and there is some possibility of [the ocean] serving as a bigger buffer for [warming].

"But we need to understand the ocean better before we can say that with confidence," he cautions.

Follow Dan Vergano on Twitter.

10 comments
Reynaldo Adams
Reynaldo Adams

this report said nothing besides the fact that humans don't know anything concerning the weather, besides how to gain credibility for a conspiracy that they help conjure up from nothing.  the heading says everything, but the actual report says nothing. and yet we still have people on the band-wagon saying humans are destroying Earth, thanx judith walker for not reading.

Daryl Johanssen
Daryl Johanssen

And it is rising more and more during storms and leaving people with no sand in front of their homes, as any individual who has ever even visited anyone who owns an oceanfront home can attest to. 

Judith Walker
Judith Walker

Its FACT that humans are DESTROYING the planet.

Ian Sloan
Ian Sloan

there is more garbage in this report than there is floating in the ocean ...

This sort of alarmist nonsense is the last busted flush of the IPCC and their acolytes, who think that no one actually has any access to the ARGO buoy system, or sea level information, and can see the absolute fallacy of this nonsense

Tyson Eheler
Tyson Eheler

This shows that global warming could be a possibility.

Albert Kappers
Albert Kappers

@Ian Sloan  can you add a link please to access the data of the ARGO buoy system that should prove the contrary? I looked for it but couldn't find it.

Laura Roerden
Laura Roerden

@Ian Sloan Could you explain both what exactly you think is garbage about this and what the motivation might be for international bodies to distort science? And your degrees and qualifications? While you're at it, I'd like a full explanation of the ocean chemistry behind your readings of the data? 


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