Climate Change Caused by the Ocean Circulation and Atmosphere

The Thermohaline Circulation or ocean conveyor belt moves heat and water between the hemispheres, along the ocean bottom. It also moves carbon dioxide.

Most of the concerns about climate change have focused on the amount of greenhouse gases that have been released into the atmosphere, but in a new study published in Science, a group of Rutgers researchers have found that circulation of the ocean plays an equally important role in regulating the earth's climate.

In their study, the researchers say the major cooling of Earth and continental ice build-up in the Northern Hemisphere 2.7 million years ago coincided with a shift in the circulation of the ocean - which pulls in heat and carbon dioxide in the Atlantic and moves them through the deep ocean from north to south until it's released in the Pacific.

The ocean conveyor system, Rutgers scientists believe, changed at the same time as a major expansion in the volume of the glaciers in the northern hemisphere as well as a substantial fall in sea levels.

It was the Antarctic ice, they argue, that cut off heat exchange at the ocean's surface and forced it into deep water. They believe this caused global climate change at that time, not carbon dioxide in the atmosphere.

"We argue that it was the establishment of the modern deep ocean circulation - the ocean conveyor - about 2.7 million years ago, and not a major change in carbon dioxide concentration in the atmosphere that triggered an expansion of the ice sheets in the northern hemisphere," says Stella Woodard, lead author and a post-doctoral researcher in the Department of Marine and Coastal Sciences.

Their findings, based on ocean sediment core samples between 2.5 million to 3.3 million years old, provide scientists with a deeper understanding of the mechanisms of climate change today.

The study shows that changes in heat distribution between the ocean basins is important for understanding future climate change.

However, scientists can't predict precisely what effect the carbon dioxide currently being pulled into the ocean from the atmosphere will have on climate.

Still, they argue that since more carbon dioxide has been released in the past 200 years than any recent period in geological history, interactions between carbon dioxide, temperature changes and precipitation, and ocean circulation will result in profound changes.

Scientists believe that the different pattern of deep ocean circulation was responsible for the elevated temperatures 3 million years ago when the carbon dioxide level in the atmosphere was arguably what it is now and the temperature was 4 degree Fahrenheit higher.

They say the formation of the ocean conveyor cooled the earth and created the climate we live in now.

"Our study suggests that changes in the storage of heat in the deep ocean could be as important to climate change as other hypotheses, tectonic activity or a drop in the carbon dioxide level, and likely led to one of the major climate transitions of the past 30 million years," says Yair Rosenthal, co-author and professor of marine and coastal sciences at Rutgers

El Niño 2014: Ocean Circulation - Signs of a modest return

The image shows Kelvin waves of high sea level (red/yellow) crossing the Pacific Ocean at the equator. 

The waves can be related to El Niño events. Green indicates normal sea level, and blue/purple areas are lower than normal. 

Data are from the NASA /European Jason-2 satellite, collected Sept. 13-22, 2014. 

Image credit: NASA/JPL-Caltech

Prospects have been fading for an El Niño event in 2014, but now there's a glimmer of hope for a very modest comeback.

Scientists warn that unless these developing weak-to-modest El Niño conditions strengthen, the drought-stricken American West shouldn't expect any relief.

The latest sea-level-height data from the NASA /European Ocean Surface Topography Mission (OSTM) /Jason-2 satellite mission show a pair of eastward-moving waves of higher sea level, known as Kelvin waves, in the Pacific Ocean, the third such pair of waves this year.

Now crossing the central and eastern equatorial Pacific, these warm waves appear as the large area of higher-than-normal sea surface heights (warmer-than-normal ocean temperatures) hugging the equator between 120 degrees west and the International Dateline.

The Kelvin waves are traveling eastward and should arrive off Ecuador in late September and early October.

A series of larger atmospheric "west wind bursts" from February through May 2014 triggered an earlier series of Kelvin waves that raised hopes of a significant El Niño event.

Just as the warming of the eastern equatorial Pacific by these waves dissipated, damping expectations for an El Niño this year, these latest Kelvin waves have appeared, resuscitating hopes for a late arrival of the event.

For an overview of 2014's El Niño prospects and Kelvin waves, please see: phys.org/news/2014-05-el-nino.html

This latest image highlights the processes that occur on time scales of more than a year but usually less than 10 years, such as El Niño and La Niña.

The image also highlights faster ocean processes such as Kelvin waves. As Patzert says, "Jason-2 is a fantastic Kelvin wave counter."

These processes are known as the interannual ocean signal. To show that signal, scientists refined data for this image by removing trends over the past 21 years, seasonal variations and time-averaged signals of large-scale ocean circulation.

For a more detailed explanation of what this type of image means, visit: sealevel.jpl.nasa.gov/science/… lninopdo/latestdata/

For a time sequence of the evolution of the 2014 El Nino, visit: sealevel.jpl.nasa.gov/science/… /latestdata/archive/