ScienceDaily
Your source for the latest research news
Follow Facebook Twitter LinkedIn Subscribe RSS Feeds Newsletters
New:
  • Lost Medieval Chapel: Cult of Disemboweled Saint
  • Old-Growth Trees More Drought Tolerant
  • Early Life Experiences: Long-Lasting Impact ...
  • Nanomaterial Cuts Fat in Specific Parts of Body
  • 3D Printing Metal-Plastic Composite Structures
  • 2,000-Year-Old Shipwreck: Complex Trade
  • Mammoth Problem With Extinction Timeline
  • Ancient DNA: Origin Story of Ashkenazi Jews
  • Landslide Risk Remains Long After a Quake
  • Physicists Observe Wormhole Dynamics
advertisement
Follow all of ScienceDaily's latest research news and top science headlines!
Science News
from research organizations

1

2

Earth's Most Prominent Rainfall Feature Creeping Northward

Date:
August 9, 2009
Source:
University of Washington
Summary:
The rain band near the equator that determines the supply of freshwater to nearly a billion people throughout the tropics and subtropics has been creeping north for more than 300 years. If the band continues to migrate at just less than a mile a year, which is the average for all the years it has been moving north, then some Pacific islands near the equator may be starved of freshwater by midcentury or sooner.
Share:
FULL STORY

The rain band near the equator that determines the supply of freshwater to nearly a billion people throughout the tropics and subtropics has been creeping north for more than 300 years, probably because of a warmer world, according to research published in the July issue of Nature Geoscience.

advertisement

If the band continues to migrate at just less than a mile (1.4 kilometers) a year, which is the average for all the years it has been moving north, then some Pacific islands near the equator – even those that currently enjoy abundant rainfall – may be drier within decades and starved of freshwater by midcentury or sooner. The prospect of additional warming because of greenhouse gases means that situation could happen even sooner.

The findings suggest "that increasing greenhouse gases could potentially shift the primary band of precipitation in the tropics with profound implications for the societies and economies that depend on it," the article says.

"We're talking about the most prominent rainfall feature on the planet, one that many people depend on as the source of their freshwater because there is no groundwater to speak of where they live," says Julian Sachs, associate professor of oceanography at the University of Washington and lead author of the paper. "In addition many other people who live in the tropics but farther afield from the Pacific could be affected because this band of rain shapes atmospheric circulation patterns throughout the world."

The band of rainfall happens at what is called the intertropical convergence zone. There, just north of the equator, trade winds from the northern and southern hemispheres collide at the same time heat pours into the atmosphere from the tropical sun. Rain clouds 30,000 feet thick in places proceed to dump as much as 13 feet (4 meters) of rain a year in some places. The band stretching across the Pacific is generally between 3 degrees and 10 degrees north of the equator depending on the time of year. It has recently been hypothesized that the intertropical convergence zone does not reside in the southern hemisphere for reasons having to do with the distribution of land masses and locations of major mountain ranges in the world, particularly the Andes mountains, that have not changed for millions of years.

The new article presents surprising evidence that the intertropical convergence zone hugged the equator some 3 ½ centuries ago during Earth's little ice age, which lasted from 1400 to 1850.

advertisement

The authors analyzed the record of rainfall in lake and lagoon sediments from four Pacific islands at or near the equator.

One of the islands they studied, Washington Island, is about 5 degrees north of the equator. Today it is at the southern edge of the intertropical convergence zone and receives nearly 10 feet (2.9 meters) of rain a year. But cores reveal a very different Washington Island in the past: It was arid, especially during the little ice age.

Among other things, the scientists looked for evidence in sediment cores of salt-tolerant microbes. On Washington Island they found that evidence in 400- to 1,000-year-old sediment underlying what is now a freshwater lake. Such organisms could only have thrived if rainfall was much reduced from today's high levels on the island. Additional evidence for changes in rainfall were provided by ratios of hydrogen isotopes of material in the sediments that can only be explained by large changes in precipitation.

Sediment cores from Palau, which lies about 7 degrees north of the equator and in the heart of the modern convergence zone, also revealed arid conditions during the little ice age.

In contrast, the researchers present evidence that the Galapagos Islands, today an arid place on the equator in the Eastern Pacific, had a wet climate during the little ice age.

advertisement

They write, "The observations of dry climates on Washington Island and Palau and a wet climate in the Galapagos between about 1420-1560/1640 provide strong evidence for an intertropical convergence zone located perennially south of Washington Island (5 degrees north) during that time and perhaps until the end of the eighteenth century."

If the zone at that time experienced seasonal variations of 7 degrees latitude, as it does today, then during some seasons it would have extended southward to at least the equator, Sachs says. This has been inferred previously from studies of the intertropical convergence zone on or near the continents, but the new data from the Pacific Ocean region is clearer because the feature is so easy to identify there.

The remarkable southward shift in the location of the intertropical convergence zone during the little ice age cannot be explained by changes in the distribution of continents and mountain ranges because they were in the same places in the little ice age as they are now. Instead, the co-authors point out that the Earth received less solar radiation during the little ice age, about 0.1 percent less than today, and speculate that may have caused the zone to hover closer to the equator until solar radiation picked back up.

"If the intertropical convergence zone was 550 kilometers, or 5 degrees, south of its present position as recently as 1630, it must have migrated north at an average rate of 1.4 kilometers – just less than a mile – a year," Sachs says. "Were that rate to continue, the intertropical convergence zone will be 126 kilometers – or more than 75 miles – north of its current position by the latter part of this century."

Other co-authors of the paper that went online June 28 are three of Sachs' former postdoctoral students, Dirk Sachse at the University of Potsdam, Germany; Rienk Smittenberg at the Swiss Federal Institute of Technology Zurich, Switzerland; and Zhaohui Zhang at the Nanjing University, China; as well as Stjepko Golubic of Boston University; and David Battisti, UW professor of atmospheric sciences.

The work was funded by the National Science Foundation, National Oceanic and Atmospheric Administration and the Gary Comer Science and Education Foundation.

make a difference: sponsored opportunity

Story Source:

Materials provided by University of Washington. Note: Content may be edited for style and length.


Cite This Page:

  • MLA
  • APA
  • Chicago
University of Washington. "Earth's Most Prominent Rainfall Feature Creeping Northward." ScienceDaily. ScienceDaily, 9 August 2009. <www.sciencedaily.com/releases/2009/07/090701135535.htm>.
University of Washington. (2009, August 9). Earth's Most Prominent Rainfall Feature Creeping Northward. ScienceDaily. Retrieved December 2, 2022 from www.sciencedaily.com/releases/2009/07/090701135535.htm
University of Washington. "Earth's Most Prominent Rainfall Feature Creeping Northward." ScienceDaily. www.sciencedaily.com/releases/2009/07/090701135535.htm (accessed December 2, 2022).

  • RELATED TOPICS
    • Earth & Climate
      • Global Warming
      • Ice Ages
      • Geography
      • Climate
      • Oceanography
      • Earth Science
      • Earthquakes
      • Atmosphere
advertisement

  • RELATED TERMS
    • Tropic of Cancer
    • San Andreas Fault
    • Tropic of Capricorn
    • Circle of latitude
    • Water scarcity
    • Bering Strait
    • Arctic Circle
    • Hadley cell
advertisement

  Print   Email   Share

advertisement

1

2

3

4

5
Most Popular
this week

PLANTS & ANIMALS
Put the Kettle On! How Black Tea (and Other Favorites) May Help Your Health Later in Life
Honey Bee Life Spans Are 50 Percent Shorter Today Than They Were 50 Years Ago
525-Million-Year-Old Fossil Defies Textbook Explanation for Brain Evolution
EARTH & CLIMATE
New Catalyst Could Be Key for Hydrogen Economy
Fossil Overturns More Than a Century of Knowledge About the Origin of Modern Birds
Earth Might Be Experiencing 7th Mass Extinction, Not 6th
FOSSILS & RUINS
Oldest Evidence of the Controlled Use of Fire to Cook Food, Researchers Report
Human Evolution Wasn't Just the Sheet Music, but How It Was Played
World's Oldest Meal Helps Unravel Mystery of Our Earliest Animal Ancestors
advertisement

Strange & Offbeat
 

PLANTS & ANIMALS
Ranches of the Future Could Be Home to Cows Wearing Smart-Watch-Style Sensors Powered by Their Movements
Flowers Show Their True Colors
Male Orb-Weaving Spiders Fight Less in Female-Dominated Colonies
EARTH & CLIMATE
A Waste Windfall: New Process Shows Promise Turning Plastic Trash Into Pharmaceuticals
DNA Sequence Enhances Understanding Origins of Jaws
Ancient Superpredator Got Big by Front-Loading Its Growth in Its Youth
FOSSILS & RUINS
Fossil Overturns More Than a Century of Knowledge About the Origin of Modern Birds
Mammoth Problem With Extinction Timeline
New Quantum Computing Feat Is a Modern Twist on a 150-Year-Old Thought Experiment
Explore More
from ScienceDaily

RELATED STORIES

Widespread Retreat and Loss of Marine-Terminating Glaciers in the Northern Hemisphere
Jan. 31, 2022 — Researchers have mapped out all the glaciers that end in the ocean in the Northern Hemisphere and provide a measure of their rate of change over the last 20 years. Their findings will help us better ...
The Arctic Ocean Was Covered by a Shelf Ice and Filled With Freshwater
Feb. 3, 2021 — The Arctic Ocean was covered by up to 900 m thick shelf ice and was filled entirely with freshwater at least twice in the last 150,000 years. This surprising finding is the result of long-term ...
Increasing Arctic Freshwater Is Driven by Climate Change
July 30, 2020 — Climate change is driving increasing amounts of freshwater into the Arctic Ocean. Within the next few decades, this will lead to increased freshwater moving into the North Atlantic Ocean, which could ...
One Wet Winter Can Shake Up San Francisco Bay's Invasive Species
Dec. 7, 2017 — For many Californians, last year's wet winter triggered a case of whiplash. After five years of drought, rain from October 2016 to February 2017 broke more than a century of records. In San Francisco ...
advertisement


SD
  • SD
    • Home Page
    • Top Science News
    • Latest News
  • Home
    • Home Page
    • Top Science News
    • Latest News
  • Health
    • View all the latest top news in the health sciences,
      or browse the topics below:
      Health & Medicine
      • Allergy
      • Alternative Medicine
      • Birth Control
      • Cancer
      • Diabetes
      • Diseases
      • Heart Disease
      • HIV and AIDS
      • Obesity
      • Stem Cells
      • ... more topics
      Mind & Brain
      • ADD and ADHD
      • Addiction
      • Alzheimer's
      • Autism
      • Depression
      • Headaches
      • Intelligence
      • Psychology
      • Relationships
      • Schizophrenia
      • ... more topics
      Living Well
      • Parenting
      • Pregnancy
      • Sexual Health
      • Skin Care
      • Men's Health
      • Women's Health
      • Nutrition
      • Diet and Weight Loss
      • Fitness
      • Healthy Aging
      • ... more topics
  • Tech
    • View all the latest top news in the physical sciences & technology,
      or browse the topics below:
      Matter & Energy
      • Aviation
      • Chemistry
      • Electronics
      • Fossil Fuels
      • Nanotechnology
      • Physics
      • Quantum Physics
      • Solar Energy
      • Technology
      • Wind Energy
      • ... more topics
      Space & Time
      • Astronomy
      • Black Holes
      • Dark Matter
      • Extrasolar Planets
      • Mars
      • Moon
      • Solar System
      • Space Telescopes
      • Stars
      • Sun
      • ... more topics
      Computers & Math
      • Artificial Intelligence
      • Communications
      • Computer Science
      • Hacking
      • Mathematics
      • Quantum Computers
      • Robotics
      • Software
      • Video Games
      • Virtual Reality
      • ... more topics
  • Enviro
    • View all the latest top news in the environmental sciences,
      or browse the topics below:
      Plants & Animals
      • Agriculture and Food
      • Animals
      • Biology
      • Biotechnology
      • Endangered Animals
      • Extinction
      • Genetically Modified
      • Microbes and More
      • New Species
      • Zoology
      • ... more topics
      Earth & Climate
      • Climate
      • Earthquakes
      • Environment
      • Geography
      • Geology
      • Global Warming
      • Hurricanes
      • Ozone Holes
      • Pollution
      • Weather
      • ... more topics
      Fossils & Ruins
      • Ancient Civilizations
      • Anthropology
      • Archaeology
      • Dinosaurs
      • Early Humans
      • Early Mammals
      • Evolution
      • Lost Treasures
      • Origin of Life
      • Paleontology
      • ... more topics
  • Society
    • View all the latest top news in the social sciences & education,
      or browse the topics below:
      Science & Society
      • Arts & Culture
      • Consumerism
      • Economics
      • Political Science
      • Privacy Issues
      • Public Health
      • Racial Disparity
      • Religion
      • Sports
      • World Development
      • ... more topics
      Business & Industry
      • Biotechnology & Bioengineering
      • Computers & Internet
      • Energy & Resources
      • Engineering
      • Medical Technology
      • Pharmaceuticals
      • Transportation
      • ... more topics
      Education & Learning
      • Animal Learning & Intelligence
      • Creativity
      • Educational Psychology
      • Educational Technology
      • Infant & Preschool Learning
      • Learning Disorders
      • STEM Education
      • ... more topics
  • Quirky
    • Top News
    • Human Quirks
    • Odd Creatures
    • Bizarre Things
    • Weird World
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:

  • Email Newsletters
  • RSS Feeds
Follow Us

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

  • Facebook
  • Twitter
  • LinkedIn
Have Feedback?

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?

  • Leave Feedback
  • Contact Us
About This Site  |  Staff  |  Reviews  |  Contribute  |  Advertise  |  Privacy Policy  |  Editorial Policy  |  Terms of Use
Copyright 1995-2022 ScienceDaily or by other parties, where indicated. All rights controlled by their respective owners.
Content on this website is for information only. It is not intended to provide medical or other professional advice.
Views expressed here do not necessarily reflect those of ScienceDaily, its staff, its contributors, or its partners.
Financial support for ScienceDaily comes from advertisements and referral programs, where indicated.
— CCPA: Do Not Sell My Information — GDPR: Privacy Settings —