A stalagmite in a West Virginia cave has yielded the most detailed geological record to date on climate cycles in eastern North America over the past 7,000 years. The new study confirms that during periods when Earth received less solar radiation, the Atlantic Ocean cooled, icebergs increased and precipitation fell, creating a series of century-long droughts.
A research team led by Ohio University geologist Gregory Springer examined the trace metal strontium and carbon and oxygen isotopes in the stalagmite, which preserved climate conditions averaged over periods as brief as a few years. The scientists found evidence of at least seven major drought periods during the Holocene era, according to an article published online in the journal Geophysical Research Letters.
“This really nails down the idea of solar influence on continental drought,” said Springer, an assistant professor of geological sciences.
Geologist Gerald Bond suggested that every 1,500 years, weak solar activity caused by fluctuations in the sun’s magnetic fields cools the North Atlantic Ocean and creates more icebergs and ice rafting, or the movement of sediment to ocean floors. Other scientists have sought more evidence of these so-called “Bond events” and have studied their possible impact on droughts and precipitation. But studies to date have been hampered by incomplete, less detailed records, Springer said.
The stalagmites from the Buckeye Creek Cave provide an excellent record of climate cycles, he said, because West Virginia is affected by the jet streams and moisture from the Gulf of Mexico and the Pacific Ocean.
Other studies have gleaned climate cycle data from lakes, but fish and other critters tend to churn the sediment, muddying the geological record there, said study co-author Harold Rowe, an assistant professor of geological sciences at the University of Texas at Arlington.
“(The caves) haven’t been disturbed by anything. We can see what happened on the scale of a few decades. In lakes of the Appalachian region, you’re looking more at the scale of a millennium,” Rowe said.
Strontium occurs naturally in the soil, and rain washes the element through the limestone. During dry periods, it is concentrated in stalagmites, making them good markers of drought, Rowe explained. Carbon isotopes also record drought, Springer added, because drier soils slow biological activity. This causes the soil to “breathe less, changing the mix of light and heavy carbon atoms in it,” he said.
In the recent study, the scientists cut and polished the stalagmite, examined the growth layers and then used a drill to take 200 samples along the growth axis. They weighed and analyzed the metals and isotopes to determine their concentrations over time.
The data are consistent with the Bond events, which showed the connection between weak solar activity and ice rafting, the researchers said. But the study also confirmed that this climate cycle triggers droughts, including some that were particularly pronounced during the mid-Holocene period, about 6,300 to 4,200 years ago. These droughts lasted for decades or even entire centuries.
Though modern records show that a cooling North Atlantic Ocean actually increases moisture and precipitation, the historic climate events were different, Springer said. In the past, the tropical regions of the Atlantic Ocean also grew colder, creating a drier climate and prompting the series of droughts, he explained.
Unfortunately, at this point the media release replaces data with computer modelled global warming alarmism:
The climate record suggests that North America could face a major drought event again in 500 to 1,000 years, though Springer said that manmade global warming could offset the cycle.
“Global warming will leave things like this in the dust. The natural oscillations here are nothing like what we would expect to see with global warming,” he said.
Though some climate and drought records exist for the Western and Midwest areas of North America, the eastern Appalachian region hasn’t been studied much to date, Rowe said. The research team plans to examine additional stalagmite records from West Virginia and Tennessee to paint a better picture of North American climate cycles.
Collaborators on the study also included Lawrence Edwards, Ben Hardt and Hai Cheng of the University of Minnesota.
Ohio University Research News – ATHENS, Ohio (Aug. 19, 2008): New climate record shows century-long droughts in eastern North America
Weak sun created cool oceans, lowered rainfall seven times in 7,000 years
Abstract:
Elevated Sr/Ca ratios and δ13C values in Holocene-age stalagmite BCC-002 from eastcentral North America record six centennial-scale droughts during the last five North Atlantic Ocean ice-rafted debris (IRD) episodes, previously ascribed to solar irradiance minima. Spectral and cross-spectral analyses of the multi-decadal resolution Sr/Ca and δ13C time series yield coherent ~200 and ~500 years periodicities. The former is consistent with the de Vries solar irradiance cycle. Cross-spectral analysis of the Sr/Ca and IRD time series yields coherent periodicities of 715- and 455-years, which are harmonics of the 1,450±500 year IRD periodicity. These coherencies corroborate strong visual correlations and provide convincing evidence for solar forcing of east-central North American droughts and strengthen the case for solar modulation of mid-continent climates. Moisture transport across North America may have lessened during droughts because of weakened north-south temperature and pressure gradients caused by cooling of the tropical Pacific and Atlantic Oceans. across the region throughout much of the year. As such, hydroclimates of eastern NA are dually sensitive to the climate state of the North AO and mid-latitude transcontinental teleconnections linking the Pacific and North Atlantic oceans [McCabe et al., 2004; Seager, 2007]. Herein, we demonstrate that this dual dependency allowed an east-central NA paleoclimate archive (speleothem) to directly record solar-forcing of Mid- to Late Holocene droughts that were caused by weakening of moisture transport over east-central NA in response to cooling of the Pacific and Atlantic Oceans.
Conclusions:
Seven significant Mid- to Late Holocene droughts are recorded in West Virginia stalagmite BCC-002 as elevated Sr/Ca ratios and δ13C values. Six droughts correlate with cooling of the Atlantic and Pacific Oceans as part of the North Atlantic Ocean ice-rafted debris cycle, which has been linked to the solar irradiance cycle. The Sr/Ca and δ13C time series display periodicities of ~200 and ~500 years and are coherent in those frequency bands. The ~200-year periodicity is consistent with the de Vries (Suess) solar irradiance cycle. We interpret the ~500- year periodicity to be a harmonic of the IRD oscillations. Visually, the Sr/Ca and IRD time series show strong correlations and cross-spectral analysis of the Sr/Ca and IRD time series yields statistically significant coherencies at periodicities of 455 and 715 years. These latter values are very similar to the second (725-years) and third (480-years) harmonics of the 1450±500-years IRD periodicity [Bond et al., 2001]. Collectively, these findings and a 1,200-year periodicity in the Sr/Ca time series, demonstrates solar forcing of droughts in east-central North America on multiple time scales. Droughts typically occur during solar minima when SST in the Atlantic and Pacific Oceans are comparatively cool. These SST anomalies cause migration of the jet stream away from east-central NA, yielding decreased meridional moisture transport and reduced convergence over east-central NA. Our findings appear to corroborate works indicating that millennial-scale solar-forcing is responsible for droughts and ecosystem changes in central and eastern North America [Viau et al., 2002; Willard et al., 2005; Dennison et al., 2007], but our high-resolution time series provide much stronger evidence in favor of solar-forcing of North American drought by yielding unambiguous spectral analysis results.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
“Weak sun created cool oceans, lowered rainfall seven times in 7,000 years”
Well, duh. The sun hasn’t been varying to that extent lately.
A 1500 year solar cycle is, er… every 1500 years.
The way this SJT character gets in first on almost every post makes me wonder if he’s a paid troll. If not, SJT, keep working at it. They say you should fake it till you make it.
Century-Long *Doubts* surely?
Don’t you just love this kinda stuff:
“(The caves) haven’t been disturbed by anything. We can see what happened on the scale of a few decades. In lakes of the Appalachian region, you’re looking more at the scale of a millennium.”
Yet here we are in good ol’ West Virginie, nearly more paleoindian sites than in the rest of the whole U. S of A e.g.:
Greenbrier County, West Virginia, 4-6 October, 2002 Led by Greg Springer, this trip will explore the balance of physical versus chemical erosion in rivers and karst in the scenic mountains of southeastern West Virginia. Highlights include exploration of Buckeye Creek Cave (about 5 miles of LARGE passages with abundant speleothems) and….
“Errr Ugg!
Yes, Grrrgg me old paleo-indian mate, nuvver nice blueberry ale mate?
Nahhh – jeeez its cold – throw another dog on the fire willya?
Sure buddy – hey would ya like me to throw yr trouble ‘n strife on the fire – been givin ya a bit o’ grief lately I hear, what with her frickin’ chillblains an’ all.
Whatever, mate – just make sure you keep the heat up front close to me bearskins. Wouldn’t want to dry out any of those stalagmites back there and stuff up those Ohio Uni geologist muffas 7000 years from now….”
Imagine that, global warming will prevent North American drought.
Idiot SJT quotes:
“Weak sun created cool oceans, lowered rainfall seven times in 7,000 years”
Than idiot SJT says:
“Well, duh. The sun hasn’t been varying to that extent lately.”
What is your point SJT? If you were going to point out anything useful you might point out that our CSIRO is blatantly lying to the public and linking warming with drought. And that therefore they ought to be either horsewhipped or we must conclude that the very stupid have become upwardly-mobile.
First, I’d like to criticize Paul for inserting the obviously incorrect editorial comment in bold. He blames the media for inserting material from computer models, when in fact the comments come from Mr. Springer himself, and do not refer to computer models.
Steve, you assert that the data from the caves was compromised by human occupation. I find that difficult to believe, for two reasons. First, the caves in question are stated to be five miles in length — that’s much too large for human occupation to significantly affect (remember, human occupation was restricted to the first hundred feet or so). Second, and more important, you have no evidence that the caves were occupied by humans. There are many cave systems that are not usable for human occupation because of the size of the entry way or the geometry of the first hundred feet. To be usable, a cave system needs a large entryway and a flat platform at the entryway. Many haves have entrances that slope steeply upwards or downwards. In the absence of evidence on this matter, ridiculing the scientists who did the work is unfair.
Lief Svalgaard says that neither Bond nor anyone else ever succeeded in proving that Bond cycles had a solar cause. This paper doesn’t appear to have done it either. IIRC there is a competing non-solar explanation for the cycles, although I can’t recall any details.
Unfortunately for residents of the southwestern U.S. (population 50M+), AGW-induced drying is already underway:
——————————-
Drier, warmer springs in US Southwest stem from human-caused changes in winds
Human-driven changes in the westerly winds are bringing hotter and drier springs to the American Southwest, according to new research from The University of Arizona in Tucson.
Since the 1970s the winter storm track in the western U.S. has been shifting north, particularly in the late winter. As a result, fewer winter storms bring rain and snow to Southern California, Arizona, Nevada, Utah, western Colorado and western New Mexico.
“We used to have this season from October to April where we had a chance for a storm,” said Stephanie A. McAfee. “Now it’s from October to March.”
The finding is the first to link the poleward movement of the westerly winds to the changes observed in the West’s winter storm pattern. The change in the westerlies is driven by the atmospheric effects of global warming and the ozone hole combined.
“When you pull the storm track north, it takes the storms with it,” said McAfee, a doctoral candidate in the UA’s department of geosciences.
“During the period it’s raining less, it also tends to be warmer than it used to be,” McAfee said. “We’re starting to see the impacts of climate change in the late winter and early spring, particularly in the Southwest. It’s a season-specific kind of drought.”
Having drier, warmer conditions occur earlier in the year will affect snowpack, hydrological processes and water resources, McAfee said.
Other researchers, including the UA’s Laboratory of Tree-Ring Research Director Tom Swetnam, have linked warmer, drier springs to more and larger forest fires.
McAfee’s co-author Joellen L. Russell said, “We’re used to thinking about climate change as happening sometime in the future to someone else, but this is right here and affects us now. The future is here.”
McAfee and Russell, a UA assistant professor of geosciences, will publish their paper, Northern Annular Mode Impact on Spring Climate in the Western United States, in Geophysical Research Letters, a journal of the American Geophysical Union. The National Oceanic and Atmospheric Administration funded the research via the Climate Assessment for the Southwest program at the UA.
Atmospheric scientists have documented that the westerly winds, or storm track, have been shifting poleward for several decades. The southwestern U.S. has experienced less winter precipitation during the same period.
Computer models of future climate and atmospheric conditions suggest the storm track will continue to move north and that precipitation will continue to decrease in the southwestern U.S.
The timing of the change from wet, cool winter weather to the warmer dry season is important for many ecological processes in the arid Southwest. Therefore, McAfee wanted to know how the shift in the storm track affected precipitation during the transition from winter to spring.
For the period 1978 to 1998, the researchers compared the month-to-month position of the winter storm track, temperature and precipitation records from the western U.S., and pressure at different levels in the atmosphere.
The team used a statistical method called Monte Carlo simulations to test whether the coincidence of storm track and weather patterns had occurred by chance.
Russell said the results of the simulation showed, “It’s very rare that you get this distribution by chance.” Therefore, she said, the changes in late winter precipitation in the West from 1978 to 1998 are related to the changes in the storm track path for that same time period.
McAfee said her next step is investigating whether western vegetation has changed as the storm track has changed.
Hmm, standard html codes don’t seem to work. The source for that was eurekalert.org.
Geesuz Steve – you have a couple years of less then average rain and some long-hair in Arizona says were getting climate change.
Here’s a clue for you – Arizona’s state flower is the Saguaro Cactus flower.
http://phoenix.about.com/library/blsaguaroflower2.htm
The saguaro flowers have a short life; they open at night and close permanently during the next day. _ Can you guess why that is?
Here’s the biggest reason why McAfee and Russell think climate change is something happening “right here and now”.
http://www.climateaudit.org/?p=1821 < behold the official climate change measureing thermometer for the University of Arizona at Tucson.
I won’t bore you with how many times, I have had to sandbag [Marine Reserves] to keep the various rivers in Sacramento behind their banks – because frankly it bores me too. It bored me back when I was doing it even. Trust me, it was a lot of times.
It seems to me that if the problem with measuring lake sediments is that fish disturb the silty bottom smearing the timeline resolution, then the solution is to study lakes that don’t have any fish.
They have plenty of steril lakes in New England due to water acidity.
“Unfortunately for residents of the southwestern U.S. (population 50M+), AGW-induced drying is already underway:”
You are just lying Bloom as usual. Its been cooling. How is cooling AGW? Idiot?
And how do you make that link between drying and CO2.
Bloom is the first liar I ever met on the internet looking into this science fraud. He never comes up with evidence and he always keeps lying.
Good point, Graeme, how can this claimed phenomena be due to global warming when the planet has not warmed for a decade or more?
How can the shift in the storm track be attributed to a global warming that has not been present for the last 1/4 of the interval?
UH…we are in a Maunder Minimum right now(..low solar activity), solar cycle 24(…each solar cycle is 11 years) is predicted to have only 94 sunspots…that is 94 in 11 years!
The last Maunder minimum lasted almost 1500 years. A professor of mine once said that you can talk about AGW all you want but the fact is the earth is in between periods of glaciation.
I hope I see this in my lifetime!
my ¢