Yawn. |
Posted on 12/22/2003 9:36:04 AM PST by cogitator
Tropical ocean waters have become dramatically saltier over the past 40 years, while oceans closer to Earth's poles have become fresher, scientists reported today in the journal Nature. Earth's warming surface may be intensifying evaporation over oceans in the low latitudes -- raising salinity concentrations there -- and transporting more fresh water vapor via the atmosphere toward Earth's poles.
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.
The study was conducted by Ruth Curry, a research specialist in the WHOI Physical Oceanography Department, Bob Dickson of the Centre for Environment, Fisheries, and Aquaculture Science in Lowestoft, United Kingdom, and Igor Yashayaev of the Bedford Institute of Oceanography in Dartmouth, Nova Scotia, Canada.
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 exacerbate global warming by rapidly adding more water vapor -- itself a potent, heat-trapping greenhouse gas -- to the atmosphere. It could also continue to freshen northern 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% of the Earth's water, experience 86% of planetary evaporation, and receive 78% of planetary precipitation, and thus represent a key element of the global water cycle for study, the scientists said. Since 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 transect in the Atlantic Ocean, from the tip of Greenland to the tip of South America. Their analysis showed that "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 observed that surface waters in tropical and subtropical Atlantic Ocean regions became markedly more saline. 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 ten 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 5% to 10% over the last 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," the authors said. 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 -- a linchpin and potential Achilles' heel in Earth's climate system. 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 waters 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 that 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 one source 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, and the Conveyor would again begin to circulate ocean waters. However, 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 supported by the National Science Foundation, 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 Woods Hole Oceanographic Institution.
So, in other words, this has happened WITHOUT human industrial activity.
sorry, resistance was futile
IT'S THE END OF THE WORLD!! AAAAAAaaaargh!!
next thing we will be presented with is, that's why whales want to beach themselves.
Too much salt for their taste!
When are these antagonistic environmental wackos going to run out of straws?
Yawn. |
And that is the unwritten platform of the Democratic Party.
Certainly. And there's no implication that human activity is causing this, because the amount of global warming due to human activity over the past century has not yet been accurately quantified.
At the end of the last glacial period (which is what "Ice Age" usually refers to), the warming trend led to the formation of very large freshwater lakes on the North American continental shelf, behind the retreating glaciers. When the ice dams broke, all of this freshwater entered the North Atlantic, causing the abrupt cessation of deepwater formation and the shutdown of the normal mode of thermohaline circulation. Global temperature literally plunged (5-10 C) and this cold period lasted for the next 1000 years -- and warmed up in 1-2 decades just as much when the circulation pattern resumed.
This possibility has been considered due to the current modest warming trend, but most research indicates that a complete shutdown of deepwater formation in the North Atlantic is unlikely. Thus, the effects of a significant alteration of the volume of deepwater formation and a significant change in the rate of thermohaline circulation are much harder to specify. Bottom line: things will change. How much, when, and where is still quite uncertain.
Yes, and perhaps somewhat increased precipitation.
The change in freezing point is insignificant compared to the effect of temperature. Deepwater formation is critically related to salinity and temperature, but freezing and thawing are much more temperature-controlled.
But... I do know that there is enough carbonate sediment at the bottom of the oceans to fully neutralize every possible CO2 molecule that could go into the atmosphere from fossil fuel energy production -- that means if every reserve (coal, oil, gas, oil shale, methane hydrates) were completely burned up. But if all of the fossil fuels were burned up in 200-300 years, it would take about 10,000 years for all of the CO2 to get into the ocean, change the seawater chemistry, accelerate the dissolution of the carbonate sediment, and then let the seawater chemistry and atmosphere evolve back to normal.
1,000 or 10,000 years is an eyeblink in a paleoclimate history that is millions of years long. So there's your answer. Earth's lifetime and many of its geological processes operate on timescales far longer than human lifetimes. In the geological perspective, the current alteration of the atmosphere is happening so fast as to be virtually unnoticeable. From the human perspective, things may change noticeably.
Right now it qualifies as an Effect. It could become a Cause.
How do you test by experiment the theory that an asteroid hit the Yucatan Peninsula about 65 million years ago?
April 2003: The global average temperature departure was 0.14°C; the Northern Hemisphere temperature departure was 0.25°C; and the Southern Hemisphere departure was 0.03°C.
Below: Monthly satellite temperatures for the Northern Hemisphere (top) and Southern Hemisphere (bottom). Trend lines indicate statistically significant changes only.
Or.. it could be since he was inside the dragon, it was the stomach acid! (or Shrek's breath!)
Also, the Solar Constant is roughly 1 kw/m2 at the surface of Earth and roughly 1379 kw/m2</sup) in space. It has been slowly INCREASING for many decades.
Also:
MIT researcher finds evidence of global warming on Neptune's largest moon
JUNE 24, 1998
CAMBRIDGE, Mass. -- We're not the only ones experiencing global warming. A Massachusetts Institute of Technology researcher has reported that observations obtained by NASA's Hubble Space Telescope and ground-based instruments reveal that Neptune's largest moon, Triton, seems to have heated up significantly since the Voyager space probe visited it in 1989. The warming trend is causing part of Triton's surface of frozen nitrogen to turn into gas, thus making its thin atmosphere denser.
While no one is likely to plan a summer vacation on Triton, this report in the June 25 issue of the journal Nature by MIT astronomer James L. Elliot and his colleagues from MIT, Lowell Observatory and Williams College says that the moon is approaching an unusually warm summer season that only happens once every few hundred years. Elliot and his colleagues believe that Triton's warming trend could be driven by seasonal changes in the absorption of solar energy by its polar ice caps.
"At least since 1989, Triton has been undergoing a period of global warming. Percentage-wise, it's a very large increase," said Elliot, professor of Earth, Atmospheric and Planetary Sciences and director of the Wallace Astrophysical Observatory. The 5 percent increase on the absolute temperature scale from about minus-392 degrees Fahrenheit to about minus-389 degrees Fahrenheit would be like the Earth experiencing a jump of about 22 degrees Fahrenheit.
Triton is a simpler subject than Earth for studying the causes and effects of global warming. "It's generally true around the solar system that when we try to understand a problem as complex as global warming -- one in which we can't control the variables -- the more extreme cases we have to study, the more we can become sure of certain factors," Elliot said. "With Triton, we can clearly see the changes because of its simple, thin atmosphere."
The moon is approaching an extreme southern summer, a season that occurs every few hundred years. During this special time, the moon's southern hemisphere receives more direct sunlight. The equivalent on Earth would be having the sun directly overhead at noon north of Lake Superior during a northern summer.
Elliot and his colleagues believe that Triton's temperature has increased because of indications that the pressure of the atmosphere has increased. Because of the unusually strong correlation between Triton's surface ice temperature and its atmospheric pressure, Elliot said scientists can infer a temperature increase of 3 degrees Fahrenheit over nine years based on its recent increase in surface vapor pressure. Any ice on Triton that warms up a little results in a big increase in atmospheric pressure as the vaporized gas joins the atmosphere.
Scientists used one of the Hubble telescope's three Fine Guidance Sensors in November 1997 to measure Triton's atmospheric pressure when the moon passed in front of a star. Two of Hubble's guidance sensors are normally used to keep the telescope pointed at a celestial target by monitoring the brightness of guide stars. The third can serve as a scientific instrument.
In this case, the guidance sensor measured a star's gradual decrease in brightness as Triton passed in front of it. The starlight got dimmer as it traveled through Triton's thicker atmosphere and then got cut off completely by the moon's total occultation of the star. This filtering of starlight through an atmosphere is similar to what happens during a sunset. As the sun dips toward the horizon, its light dims because it is traveling through denser air and because the sun's disk gets "squashed."
By detecting that Triton's atmosphere had thickened, astronomers were able to deduce that the temperature of the ice on Triton's surface has increased. "This pressure increase implies a temperature increase," Elliot wrote. "At this rate, the atmosphere has at least doubled in bulk since the time of the Voyager encounter." Like the Earth, Triton's atmosphere is composed mostly of molecular nitrogen, but its surface pressure is much less than that of the Earth--about the same as that 45 miles high in the Earth's atmosphere.
In their Nature paper, Elliot and his colleagues list two other possible explanations for Triton's warmer weather. Because the frost pattern on Triton's surface may have changed over the years, it may be absorbing a little more of the sun's warmth. Or changes in reflectivity of Triton's ice may have caused it to absorb more heat. "When you're so cold, global warming is a welcome trend," said Elliot.
About the same size and density as Pluto, Triton--one of Neptune's eight moons--is 30 times as far from the sun as the Earth. It is very cold and windy, with winds close to the speed of sound, and has a mixed terrain of icy regions and bare spots. Triton is a bit smaller than our moon, but its gravity is able to keep an atmosphere from completely escaping because it is so cold. Its composition is believed to be similar to a comet's, although it is much larger than a comet. Triton was captured into a reverse orbit by Neptune's strong gravitational pull.
Other astronomers who participated in this investigation are MIT research assistant Heidi B. Hammel and technical assistants Michael J. Person and Stephen W. McDonald of MIT; Otto G. Franz, Lawrence H. Wasserman, John A. Stansberry, John R. Spencer, Edward W. Dunham, Catherine B. Olkin and Mark W. Buie of Lowell Observatory; Jay M. Pasachoff, Bryce A. Babcock and Timothy H. McConnochie of Williams College.
This work is supported in part by NASA, the National Science Foundation and the National Geographic Society.
The actual paper is in the journal Nature. That's where the beef (and the numbers) are.
Unless you're a trained oceanographer, you probably wouldn't be able to grasp the significance of the actual numbers -- the graphic presentation is much more effective.
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We need to have an international panel of smart people to tell everybody what to do. Otherwise, we will have global catastrophe.