PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Global ocean currents explain why Northern Hemisphere is the soggier one

2013-10-21
(Press-News.org) Contact information: Hannah Hickey
hickeyh@uw.edu
206-543-2580
University of Washington
Global ocean currents explain why Northern Hemisphere is the soggier one

A quick glance at a world precipitation map shows that most tropical rain falls in the Northern Hemisphere. The Palmyra Atoll, at 6 degrees north, gets 175 inches of rain a year, while an equal distance on the opposite side of the equator gets only 45 inches. Scientists long believed that this was a quirk of the Earth's geometry – that the ocean basins tilting diagonally while the planet spins pushed tropical rain bands north of the equator. But a new University of Washington study shows that the pattern arises from ocean currents originating from the poles, thousands of miles away.

The findings, published Oct. 20 in Nature Geoscience, explain a fundamental feature of the planet's climate, and show that icy waters affect seasonal rains that are crucial for growing crops in such places as Africa's Sahel region and southern India.

In general, hotter places are wetter because hot air rises and moisture precipitates out.

"It rains more in the Northern Hemisphere because it's warmer," said corresponding author Dargan Frierson, a UW associate professor of atmospheric sciences. "The question is: What makes the Northern Hemisphere warmer? And we've found that it's the ocean circulation."

Frierson and his co-authors first used detailed measurements from NASA's Clouds and Earth's Radiant Energy System, or CERES, satellites to show that sunlight actually provides more heat to the Southern Hemisphere – and so, by atmospheric radiation alone, the Southern Hemisphere should be the soggier one.

After using other observations to calculate the ocean heat transport, the authors next used computer models to show the key role of the huge conveyor-belt current that sinks near Greenland, travels along the ocean bottom to Antarctica, and then rises and flows north along the surface. Eliminating this current flips the tropical rain bands to the south.

The reason is that as the water moves north over many decades it gradually heats up, carrying some 400 trillion (that's four with 14 zeroes after it) watts of power across the equator.

For many years, slanting ocean basins have been the accepted reason for the asymmetry in tropical rainfall.

"But at the same time, a lot of people didn't really believe that explanation because it's kind of a complicated argument. For such a major feature there's usually a simpler explanation," Frierson said.

The ocean current they found to be responsible was made famous in the 2004 movie "The Day After Tomorrow," in which the premise was that the overturning circulation shut down and New York froze over. While a sudden shutdown like in the movie won't happen, a gradual slowing – which the recent United Nations report said was "very likely" by 2100 – could shift tropical rains south, the study suggests, as it probably has in the past.

The slowdown of the currents is predicted because increasing rain and freshwater in the North Atlantic would make the water less dense and less prone to sinking.

"This is really just another part of a big, growing body of evidence that's come out in the last 10 or 15 years showing how important high latitudes are for other parts of the world," Frierson said.

Frierson's earlier work shows how the changing temperature balance between hemispheres influences tropical rainfall. A recent study by Frierson and collaborators looked at how pollution from the industrial revolution blocked sunlight to the Northern Hemisphere in the 1970s and '80s and shifted tropical rains to the south.

"A lot of the changes in the recent past have been due to air pollution," Frierson said. "The future will depend on air pollution and global warming, as well as ocean circulation changes. That makes tropical rainfall particularly hard to predict."



INFORMATION:

Co-authors of the paper are Yen-Ting Hwang, Elizabeth Maroon, Xiaojuan Liu and David Battisti at the UW; Neven Fuckar at the University of Hawaii; Richard Seager at Columbia University; Sarah Kang at South Korea's Ulsan National Institute of Science and Technology; and Aaron Donohoe at the Massachusetts Institute of Technology.

The research was funded by the National Science Foundation, the Japan Agency for Marine-Earth Science and Technology, the National Aeronautic and Space Administration, the National Oceanic and Atmospheric Administration and the U.S. Department of Defense.

For more information, contact Frierson at 206-685-7364 or dargan@atmos.washington.edu.



ELSE PRESS RELEASES FROM THIS DATE:

2 genetic wrongs make a biochemical right

2013-10-21
2 genetic wrongs make a biochemical right Genetic mutation found to restore translational balance in mice WORCESTER, MA – In a biological quirk that promises to provide researchers with a new approach for studying and potentially treating ...

Flu virus wipes out immune system's first responders to establish infection

2013-10-21
Flu virus wipes out immune system's first responders to establish infection CAMBRIDGE, Mass. (October 20, 2013) -- Revealing influenza's truly insidious nature, Whitehead Institute scientists have discovered that the virus is able to infect its ...

Blood stem cells age at the unexpected flip of a molecular switch

2013-10-21
Blood stem cells age at the unexpected flip of a molecular switch Scientists report in Nature they have found a novel and unexpected molecular switch that could become a key to slowing some of the ravages of getting older as it prompts blood ...

Mixing nanoparticles to make multifunctional materials

2013-10-21
Mixing nanoparticles to make multifunctional materials Standardized technique opens remarkable opportunities for 'mix and match' materials fabrication UPTON, NY-Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have developed ...

Rats! Humans and rodents process their mistakes

2013-10-21
Rats! Humans and rodents process their mistakes Study finds parallels in neural processing of 'adaptive control' PROVIDENCE, R.I. [Brown University] — People and rats may think alike when they've made a mistake and are trying to adjust their thinking. That's ...

Cells' 'molecular muscles' help them sense and respond to their environments

2013-10-21
Cells' 'molecular muscles' help them sense and respond to their environments Johns Hopkins researchers used suction to learn that individual "molecular muscles" within cells respond to different types of force, a finding that may explain how cells "feel" the ...

Inherited gene variation tied to high-risk pediatric leukemia and greater risk of relapse

2013-10-21
Inherited gene variation tied to high-risk pediatric leukemia and greater risk of relapse Study led by St. Jude Children's Research Hospital finds an inherited gene variation -- more common among Hispanic Americans -- is tied to increased risk of developing ...

Clean living is a luxury wild animals can't afford, study suggests

2013-10-21
Clean living is a luxury wild animals can't afford, study suggests Domestic animals will choose to steer clear of dirt – but their wild cousins can't be so picky and may be at increased risk of disease as a result. A study of wild mice has shown that ...

Large-scale deep re-sequencing reveals cucumber's evolutionary enigma

2013-10-21
Large-scale deep re-sequencing reveals cucumber's evolutionary enigma The latest study was published online in Nature Genetics October 20, 2013, Shenzhen, China - In a collaborative study published online today in Nature Genetics, researchers from the Genome Centre of Chinese Academy of Agricultural ...

Neuron 'claws' in the brain enable flies to distinguish 1 scent from another

2013-10-21
Neuron 'claws' in the brain enable flies to distinguish 1 scent from another Cold Spring Harbor, NY -- Think of the smell of an orange, a lemon, and a grapefruit. Each has strong acidic notes mixed with sweetness. And yet each fresh, bright scent is ...

LAST 30 PRESS RELEASES:

Climate crisis could force wild vanilla plants and pollinating insects apart, threatening global supply

Teens report spending 21% of each driving trip looking at their phone

Study explores the ‘social norms’ of distracted driving among teens

Diver-operated microscope brings hidden coral biology into focus

Enhancing the “feel-good” factor of urban vegetation using AI and street view images

A single genetic mutation may have made humans more vulnerable to cancer than chimpanzees

Innovative nanocomposite hydrogel shows promise for cartilage regeneration in osteoarthritis treatment

2025 Guangci Laboratory Medicine Innovation and Development Conference

LabMed Discovery is included in the ICI World Journals database

LabMed Discovery is included in the China Open Access Journal (COAJ) database

Vaccination support program reduces pneumonia-related mortality by 25 percent among the elderly

Over decades, a healthy lifestyle outperforms metformin in preventing onset of Type 2 diabetes

Mental health disorders, malaria, and heart disease most affected by covid pandemic

Green transition will boost UK productivity

Billions voted in 2024, but major new report exposes cracks in global democracy

Researchers find “forever chemicals” impact the developing male brain

Quantum leap in precision sensing across technologies

Upgrading biocrude oil into sustainable aviation fuel using zeolite-supported iron-molybdenum carbide nanocatalysts

For effective science communication, ‘just the facts’ isn’t good enough

RT-EZ: A golden gate assembly toolkit for streamlined genetic engineering of rhodotorula toruloides

Stem Cell Reports announces five new early career editors

Support networks may be the missing link for college students who seek help for excessive drinking

The New England Journal of Medicine shines spotlight on forensic pathology

Scientists discover protein that helps lung cancer spread to the brain

Perceived social status tied to cardiovascular risks in women but not in men

Brain tumor growth patterns may help inform patient care management

This might be America's first campus tree inventory

Emoji use may impact relationship outcomes

Individual merit, not solidarity, prioritized by early childhood education policies

Preclinical study unlocks a mystery of rapid mouth healing

[Press-News.org] Global ocean currents explain why Northern Hemisphere is the soggier one