Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. 24/7 Space News .




EARLY EARTH
Multiple proxy datasets can clarify ancient climate regimes
by Staff Writers
University Park PA (SPX) Jul 04, 2012


The analyzed lake sediments contain calcium carbonate in the form of calcite. The oxygen isotope ratios in this mineral relate directly to the isotope ratio of water in the lake. The researchers looked at sediment from two small lakes in Washington state. Castor Lake is on a plateau and water inflow is only from precipitation and groundwater.

Tree ring and oxygen isotope data from the U.S. Pacific Northwest do not provide the same information on past precipitation, but rather than causing a problem, the differing results are a good thing, according to a team of geologists. The researchers are trying to understand the larger spatial patterns and timing of drought in the arid and semiarid areas of the American West.

"We generally understand that the Medieval Climate Anomaly, a warm period in much of the northern hemisphere that occurred about 950 to 1250 was a dry period in the American West," said Byron A. Steinman, postdoctoral researcher in meteorology, Penn State. "But there is complexity to the patterns of drought and it may not have been dry in winter in the Pacific Northwest."

East of the Cascade Mountains, the Pacific Northwest is dry and hot in the summer and wet in the winter now.

Estimates of past precipitation are made from proxies like tree rings, which can record amounts of precipitation and temperature. But tree rings are better at recording what happens during the spring and summer, when the tree is growing, than in the winter when the tree is not.

Steinman, who worked with Mark B. Abbott, professor of geology and planetary science, University of Pittsburgh, his Ph.D. advisor, looked at oxygen isotopes found in 1,500 years of sediment at the bottom of lakes. The isotopic composition of these sediments can reflect the amount of water that enters the lake, especially during the wet season.

The analyzed lake sediments contain calcium carbonate in the form of calcite. The oxygen isotope ratios in this mineral relate directly to the isotope ratio of water in the lake. The researchers looked at sediment from two small lakes in Washington state. Castor Lake is on a plateau and water inflow is only from precipitation and groundwater.

This lake has no outflow, so most water loss is through evaporation. Lime Lake, on the other hand, loses the majority of water through a permanent outflow stream, although all water enters in the same manner as for Castor Lake. By comparing the two lakes, the researchers could determine the water balance between evaporation and precipitation.

The researchers looked at two stable isotopes of oxygen - oxygen 16 and oxygen 18 - in the sediments. Oxygen 16 is lighter than oxygen 18, so during evaporation and lake draw down, more oxygen 16 evaporates out and the calcite in the sediments contain more oxygen 18. If the lakes are full of water, then there will be more oxygen 16 in the calcite.

The layers of sediment that are laid down each year can be dated either by using carbon 14 dating of organic material or by locating layers of tephra - volcanic ash, that signifies known - dated volcanic eruptions. In this way, the researchers could pinpoint when drought occurred.

"The tree ring data and isotope data match up on a short term, decadal scale," said Steinman. "On a longer term, century scale, the records diverge."

While the decadal ups and down remain the same for both proxies, when viewed on a 100-year or longer scale, the proxies show differences. The tree ring data suggest dry conditions during the Medieval Climate Anomaly summers, while the isotope data suggests wetter than expected winters.

Comparing the lake sediment records to existing records of the Pacific Decadal Oscillation, a warming or cooling of the coastal waters off the Pacific Northwest, the researchers report in the current online issue of the Proceedings of the National Academy of Sciences "a strong centennial timescale relationship over the past 1,500 years between winter precipitation amounts in eastern Washington and Pacific Decadal Oscillation temperature anomalies."

The PDO is linked to the El Nino Southern Oscillation, a tropical phenomenon that influences global weather patterns. During and before the Medieval Climate Anomaly, the North Pacific Ocean was warmer and Washington had greater precipitation than during the Little Ice Age, which occurred from about 1450 to 1850, when there was less precipitation.

Steinman used a previously published and validated model based on established lake physics and modern recorded precipitation and temperature to determine the amounts of rainfall indicated by the isotopic record

"The best thing we could do now is to produce additional quantitative precipitation records, this time with different lake systems," said Steinman.

.


Related Links
Penn State
Explore The Early Earth at TerraDaily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





EARLY EARTH
U Alberta resets date of earliest animal life by 30 million years
Edmonton, Canada (SPX) Jul 03, 2012
University of Alberta researchers have uncovered physical proof that animals existed 585 million years ago, 30 million years earlier than all previous established records show. The discovery was made U of A geologists Ernesto Pecoits and Natalie Aubet in Uruguay. They found fossilized tracks of a centimetre long, slug-like animal left behind 585 million years ago in a silty sediment. ... read more


EARLY EARTH
ESA to catch laser beam from Moon mission

Researchers Estimate Ice Content of Crater at Moon's South Pole

Researchers find evidence of ice content at the moon's south pole

Nanoparticles found in moon glass bubbles explain weird lunar soil behaviour

EARLY EARTH
Fireworks Over Mars: The Spirit of 76 Pyrotechnics

Martian moon Phobos could be life clue

Exhumed rocks reveal Mars water ran deep

Houston Workshop Marks Key Step in Planning Future Mars Missions

EARLY EARTH
Orion's First Test Flight Offers SLS a First Look at Hardware Operation, Integration

The Road to Space

NASA Unveils Orion During Ceremony

Boeing Validates Performance of CST Vehicle's Attitude Control Engine

EARLY EARTH
China open to cooperation

China set to launch bigger space program

Nation has long way to go as space power

An inspiring mission

EARLY EARTH
ESA astronaut Andre Kuipers returns to Earth

First Annual ISS Research and Development Conference in Review

Three astronauts land on Earth from ISS in Russian capsule

ISS crew rests before return to Earth

EARLY EARTH
Avanti Announces Launch Date for HYLAS 2 Satellite

Three Pratt and Whitney Rocketdyne RS-68A Engines Power Delta IV Heavy Upgrade Vehicle on Inaugural Flight

ULA Delta IV Heavy Launches Second Payload in Nine Days for the NRO

ATK Completes Software TIM for Liberty under NASA's Commercial Crew Program

EARLY EARTH
New Planet-weighing Technique Found

Innovative technique enables scientists to learn more about elusive exoplanet

Dramatic change spotted on a faraway planet

New Way of Probing Exoplanet Atmospheres

EARLY EARTH
Deep-sea rare earths found in Japan

Toshiba fined in US antitrust case

Tablet PCs poised to take over PC market

SACLA draws acclaim for unique XFEL design




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement