Featured Research

from universities, journals, and other organizations

New Study Reports Large-Scale Salinity Changes In The Oceans

Date:
December 18, 2003
Source:
National Science Foundation
Summary:
Tropical ocean waters have become dramatically saltier over the past 40 years, while oceans closer to Earth’s poles have become fresher, scientists report in the December 18th issue of the journal Nature.

Arlington, Va. -- Tropical ocean waters have become dramatically saltier over the past 40 years, while oceans closer to Earth’s poles have become fresher, scientists report in the December 18th issue of the journal Nature. These large-scale, relatively rapid oceanic changes suggest that recent climate changes, including global warming, may be altering the fundamental planetary system that regulates evaporation and precipitation and cycles fresh water around the globe.

Related Articles


The study was conducted by Ruth Curry of the Woods Hole Oceanographic Institution (WHOI); Bob Dickson of the Centre for Environment, Fisheries, and Aquaculture Science in Lowestoft, U.K.; and Igor Yashayaev of the Bedford Institute of Oceanography in Dartmouth, Canada.

"This study is important because it provides direct evidence that the global water cycle is intensifying," said Elise Ralph, associate director of the National Science Foundation's (NSF) physical oceanography program, which funded the research. "This is consistent with global warming hypotheses that suggest ocean evaporation will increase as Earth's temperature does. These issues are particularly important as pressure on freshwater resources has become critical in many areas around the world."

An acceleration of Earth's global water cycle can potentially affect global precipitation patterns that govern the distribution, severity and frequency of droughts, floods and storms. It would also exacerbate global warming by rapidly adding more water vapor—itself a potent, heat-trapping greenhouse gas—to the atmosphere. And it could continue to freshen North Atlantic Ocean waters to a point that could disrupt ocean circulation and trigger further climate changes.

The oceans and atmosphere continually exchange fresh water. Evaporation over warm, tropical and subtropical oceans transfers water vapor to the atmosphere, which transports it toward both poles. At higher latitudes, that water vapor precipitates as rain or snow and ultimately returns to the oceans, which complete the cycle by circulating fresh water back toward the equator. The process maintains a balanced distribution of water around our planet.

The oceans contain 96 percent of the Earth's water, experience 86 percent of planetary evaporation, and receive 78 percent of planetary precipitation, and thus represent a key element of the global water cycle for study, the scientists said. Because evaporation concentrates salt in the surface ocean, increasing evaporation rates cause detectable spikes in surface ocean salinity levels. In contrast, salinity decreases generally reflect the addition of fresh water to the ocean through precipitation and runoff from the continents.

Curry, Dickson, and Yashayaev analyzed a wealth of salinity measurements collected over recent decades along a key region in the Atlantic Ocean, from the tip of Greenland to the tip of South America. Their analysis showed the properties of Atlantic water masses have been changing—in some cases radically—over the five decades for which reliable and systematic records of ocean measurements are available, the scientists report.

They observed that surface waters in tropical and subtropical Atlantic Ocean regions became markedly saltier. Simultaneously, much of the water column in the high latitudes of the North and South Atlantic became fresher.

This trend appears to have accelerated since 1990—when 10 of the warmest years since records began in 1861 have occurred. The scientists estimated that net evaporation rates over the tropical Atlantic have increased by five percent to ten percent over the past four decades.

These results indicate that fresh water has been lost from the low latitudes and added at high latitudes, at a pace exceeding the ocean circulation's ability to compensate, say the scientists. Taken together with other recent studies revealing parallel salinity changes in the Mediterranean, Pacific, and Indian Oceans, a growing body of evidence suggests that the global hydrologic cycle has revved up in recent decades.

Among other possible climate impacts, an accelerated evaporation - precipitation cycle would continue to freshen northern North Atlantic waters. The North Atlantic is one of the few places on Earth where surface waters become dense enough to sink to the abyss. The plunge of this great mass of cold, salty water helps drive a global ocean circulation system, often called the Ocean Conveyor. This Conveyor helps draw warm Gulf Stream waters northward in the Atlantic, pumping heat into the northern regions that significantly moderates wintertime air temperatures, especially in Europe.

If the North Atlantic becomes too fresh, its waters would stop sinking and the Conveyor could slow down. Analyses of ice cores, deep-sea sediment cores, and other geologic evidence have clearly demonstrated the Conveyor has abruptly slowed down or halted many times in Earth's history. That has caused the North Atlantic region to cool significantly and brought long-term drought conditions to other areas of the Northern Hemisphere over time spans as short as years to decades.

Melting glaciers and Arctic sea ice, another consequence of global warming, are other sources of additional fresh water to the North Atlantic. An accelerated water cycle also appears to be increasing precipitation in higher latitudes, contributing to the freshening of North Atlantic waters and increasing the possibility of slowing the Conveyor.

A cooling of the North Atlantic region would slow the melting process, curtail the influx of fresh water to the North Atlantic. The Conveyor would again begin to circulate ocean waters. But global warming and an accelerated water cycle would continue to bring fresh water to high latitudes—possibly enough to maintain a cap on the Conveyor even if the Arctic melting ceased. Monitoring Earth's hydrological cycle is critical, the scientists said, because of its potential near-term impacts on Earth's climate.

The research was also supported by the Framework V Programme of the European Community, the National Oceanic and Atmospheric Administration's Consortium on the Ocean's Role in Climate, and the Ocean and Climate Change Institute at the Woods Hole Oceanographic Institution.


Story Source:

The above story is based on materials provided by National Science Foundation. Note: Materials may be edited for content and length.


Cite This Page:

National Science Foundation. "New Study Reports Large-Scale Salinity Changes In The Oceans." ScienceDaily. ScienceDaily, 18 December 2003. <www.sciencedaily.com/releases/2003/12/031218075158.htm>.
National Science Foundation. (2003, December 18). New Study Reports Large-Scale Salinity Changes In The Oceans. ScienceDaily. Retrieved October 23, 2014 from www.sciencedaily.com/releases/2003/12/031218075158.htm
National Science Foundation. "New Study Reports Large-Scale Salinity Changes In The Oceans." ScienceDaily. www.sciencedaily.com/releases/2003/12/031218075158.htm (accessed October 23, 2014).

Share This



More Earth & Climate News

Thursday, October 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Dances With Wolves in China's Wild West

Dances With Wolves in China's Wild West

AFP (Oct. 23, 2014) One man is on a mission to boost the population of wolves in China's violence-wracked far west. The animal - symbol of the Uighur minority there - is under threat with a massive human resettlement program in the region. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
San Diego Zoo's White Rhinos Provide Hope for the Critically Endangered Species

San Diego Zoo's White Rhinos Provide Hope for the Critically Endangered Species

Reuters - Light News Video Online (Oct. 22, 2014) The pair of rare white northern rhinos bring hope for their species as only six remain in the world. Elly Park reports. Video provided by Reuters
Powered by NewsLook.com
Trick-or-Treating Banned Because of Polar Bears

Trick-or-Treating Banned Because of Polar Bears

Buzz60 (Oct. 21, 2014) Mother Nature is pulling a trick on the kids of Arviat, Canada. As Mara Montalbano (@maramontalbano) tells us, the effects of global warming caused the town to ban trick-or-treating this Halloween. Video provided by Buzz60
Powered by NewsLook.com
Traditional Farming Methods Gaining Ground in Mali

Traditional Farming Methods Gaining Ground in Mali

AFP (Oct. 20, 2014) He is leading a one man agricultural revolution in Mali - Oumar Diatabe uses traditional farming methods to get the most out of his land and is teaching others across the country how to do the same. Duration: 01:44 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins