paleoclimatology

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Smithsonian Scientist and Collaborators Revise Timeline of Human Origins

Many traits unique to humans were long thought to have originated in the genus Homo between 2.4 and 1.8 million years ago in Africa. Although scientists have recognized these characteristics for decades, they are reconsidering the true evolutionary factors that drove them. […]

[Smithsonian paleoanthropologist] Richard Potts developed a new climate framework for East African human evolution that depicts most of the era from 2.5 million to 1.5 million years ago as a time of strong climate instability and shifting intensity of annual wet and dry seasons. This framework, which is based on Earth’s astronomical cycles, provides the basis for some of the paper’s key findings, and it suggests that multiple coexisting species of Homo that overlapped geographically emerged in highly changing environments.

“Unstable climate conditions favored the evolution of the roots of human flexibility in our ancestors,” said Potts, curator of anthropology and director of the Human Origins Program at the Smithsonian’s National Museum of Natural History. “The narrative of human evolution that arises from our analyses stresses the importance of adaptability to changing environments, rather than adaptation to any one environment, in the early success of the genus Homo.”

Read the article

Scientists at the University of Hong Kong have used a Granger causality analysis to establish a relationship between climate shifts and impacts on human society during the period between 1500 and 1800.

Pictured: the Battle of White Mountain during the Thirty Years’ War, a conflict that occurred during several decades of particularly cold weather in Europe.

Ancient Giant Trees Found Petrified in Thailand

“Fossil trees that approached the heights of today’s tallest redwoods have been found in northern Thailand. The longest petrified log measures 72.2 meters (237 feet), which suggest the original tree towered to more than 100 meters (330 feet) in a wet tropical forest some 800,000 years ago.

The trees appear to have been closely related to a species alive today called Koompassia elegans, which belongs to the same family as beans, peas and black locust trees, explained lead author of the study, Marc Philippe of France’s University of Lyon. That is to say, the ancient trees are not closely related to today’s tallest trees, which are the Eucalyptus (gum trees) of Australia andSequoia (redwoods) of California. Both of those living trees can reach about 130 meters (425 feet) in height.

Interestingly, there are no trees living today in Thailand that approach the size of the ancients.

Global Warming Pushing Trees North: The Evidence

“Highest trees nowadays in Thailand are almost 60 meters (200 feet),” wrote Philippe in response to my email query about his new paper coming out in the April issue of the journal Quaternary Science Reviews. ”To my knowledge the highest tree yet recorded in Thailand is a Krabak tree, belonging to the Dipterocarpaceae (‘tropical oaks’), 58 meters (190 feet) tall.”

The sediments in which the fossil trees were found suggest that they lived in a wet forest at the edge of a lowland plain. Today the fossil trees are at an elevation of 170 meters (550 feet) above sea level and the climate flips between wet and dry seasons — what’s called monsoonal. Philippe says it’s possible there has been some uplift of the region since the trees fell” (read more).

(Source: Discovery News)

Hansen et al. on Past and Future Heat

Jim Hansen of NASA has sent a fresh warning to his e-mail list (details below) concluding in a draft paper that past warm spells between ice ages were barely warmer than the present, with a host of implications. I’m sending a query around to a batch of paleoclimatologists and geologists to get reactions. Here’s the Hansen note with links to this paper and another: 

Keep reading

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The Other Carbon Dioxide Problem (by NOAAVisualizations)

Fundamental changes in seawater chemistry are occurring throughout the world’s oceans. Since the beginning of the industrial revolution, the release of carbon dioxide (CO2) from humankind’s industrial and agricultural activities has increased the amount of CO2 in the atmosphere. The ocean absorbs almost a third of the CO2 we release into the atmosphere every year, so as atmospheric CO2 levels increase, so do the levels in the ocean. Initially, many scientists focused on the benefits of the ocean removing this greenhouse gas from the atmosphere. However, decades of ocean observations now show that there is also a downside — the CO2 absorbed by the ocean is changing the chemistry of the seawater, a process called ocean acidification. This change in the ocean’s chemistry will have profound effects on life in the ocean, and those who depend on it.

An integrated remote sensing and GIS analysis of the Kufrah Paleoriver, Eastern Sahara

Ghoneim, E., M. Benedetti, and F. El-Baz, 2012: “An integrated remote sensing and GIS analysis of the Kufrah Paleoriver, Eastern Sahara.” Geomorphology, v. 139–140, pp. 242-257, doi: 10.1016/j.geomorph.2011.10.025.

A combined remote sensing (optical and radar imagery) and GIS (hydrologic network delineation) analysis allows mapping of the Kufrah Paleoriver of Libya and sheds light on its geomorphic evolution during the Neogene. The Kufrah system, which is now largely buried beneath the windblown sands of the Eastern Sahara, drained an area of about 236,000 sq km in central and southern Libya. The river discharged across a large inland delta to the Al-Jaghbub depression in northern Libya, and ultimately through the Sirt Basin to the Mediterranean Sea. Radar imagery reveals buried features of the landscape including drainage divides, locations of possible stream capture, deeply-incised valleys, and the distal margins of the inland delta. Previous studies have shown that the Kufrah Paleoriver is the successor of the Sahabi River, which drained most of central Libya during the late Tertiary. Satellite imagery supports the concept of large-scale drainage rearrangement in the Quaternary, driven by tectonic subsidence that diverted streamflow and sediment discharge away from the Sahabi basin toward the inland delta of the lower Kufrah basin. Paleochannels crossing the delta suggest that at various times during the Quaternary, the Kufrah Paleoriver either drained externally through the deeply-incised Sahabi Paleochannel to the Mediterranean Sea, or drained internally to paleolakes in the Al-Jaghbub depression. Thick alluvial deposits on the delta and lake margins likely provided a major sediment source to build the Great Sand Sea, which covers the region today. The southwestern branch of the Kufrah drainage is aligned with an elongated trough that connects to the Amatinga River system in Chad. Thus the Kufrah watershed may have served as an outlet from Megalake Chad to the Mediterranean Sea during humid phases of the Neogene. If so, the combined Amatinga/Kufrah system may have served as one of the proposed natural corridors used by human and animal populations to cross the Sahara during the Pleistocene. These findings hold promise for modeling past lake levels and paleoclimates, locating groundwater sources in the region, and exploring for reservoirs of oil and natural gas in the region.

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Strong chaos induced by close encounters with Ceres and Vesta

We show here that when we consider their collective effect, the motions of the main asteroids are much more chaotic than previously thought. This is particularly true for the motions of the largest asteroids, Ceres and Vesta, which can be mistakenly considered as regular when their mutual perturbations are not taken into account. More important, the strong interactions during close encounters also affect the planetary motions, and appear as the main limiting factor for establishing very long-term planetary solution for the Earth eccentricity, beyond 60 Myr, which would be useful for paleoclimate studies. Moreover, this limit appears to be an absolute limitation, because the horizon of predictability for the motion of Ceres and Vesta is less than 500 kyr (Fig. 3).

via Astronomy & Astrophysics

What is a typical work day for a geologist?

That question is what led to the creation of this blog.  There really is no typical work day for a geologist.  Being a geologist is nothing like working on an assembly line.  The American Institute of Professional Geologists (AIPG) has recognized more than 40 distinct disciplines within the job title called “geologist.”  So it’s pretty much impossible to describe a typical day for any of us.

I’ve been a geologist for more than 30 years.  In all that time, no two days have been exactly the same.  I’ve never been bored.  Frustrated from time to time for sure, but never bored. 

Since my very early days, I’ve done all of these things and more.

  • Studied air photos, satellite photos and other imagery, and then traveled to the locations on the ground to verify what I saw.
  • Collected rock samples and then specified what kind of analysis needed to be done.
  • Identified rocks and minerals.
  • Created maps using nothing more than a blank sheet of paper, a compass, a protractor, a ruler and a pencil.
  • Written reports that ended up in Federal Court—and we won.
  • Driven four wheel drive vehicles in the back country, and then hiked in the rest of the way.
  • Sat and listened to elderly geologists and mining engineers tell stories of what they did when they were my age, and learned a whole lot from them.  And years later, realized that younger geologists were listening to me with the same attention—much to my surprise.
  • Changed tires in swarms of mosquitoes.
  • Made stupid mistakes once, but not twice.
  • Mapped underground mines.
  • Held gold nuggets in my hand, and no, I didn’t get to keep them.
  • Learned how to perform fire assays for gold.
  • Became the coauthor of a textbook that received some unexpected acclaim and recognition, but not in my own country.

There really is no typical day for a geologist.  A lot of it depends on the general area that a person ends up working in.  I started out as an English major, but took a class in geology and was hooked.  Really, it didn’t take much hooking.  In high school, I had been a bit player in the first Earth Day. Learning about geology is learning about the Earth and all of its processes.  What we learn about Historical Geology can cause us to be annoying in conversations, sometimes, especially when we bring up paleoclimatology.

So I changed my major to Geology thinking that I’d have more job opportunities and that I’d work with people that weren’t as weird, and wouldn’t have to work behind a desk as much.  Now after more than 30 years, I find myself behind a desk more often than not.  But the work is highly rewarding.  Much of what I do has benefits far beyond just my cluttered desk.  We all use resources, and those resources must be used wisely.  And that’s where my work has taken me. 

The money hasn’t been spectacular.   The work has been regular, although I recognize that it wasn’t for all geologists of my generation.  But I’d do it all over again.

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Microfossils Reveal Climatic History of the Gulf of Mexico (by usgs)

Proxy data such as tree rings, ice cores, and microorganisms are collected and analyzed by scientists to unlock past climate records stretching back thousands to millions of years ago. This video podcast examines how scientists can decipher past climate from such records by focusing on a proxy calibration study in the Gulf of Mexico. Microfossils recovered from the northern Gulf of Mexico are used to assess the control of temperature and salinity on the composition of microfossil assemblages and the chemical composition of their shells. The new data will be used to develop better estimates of past conditions from analyses of microfossils in sediment cores.

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Some climate campaigners love to toss around the word “unprecedented" in describing extreme weather phenomena. It’s as if they never read the seminal papers on truly extreme storminess over northeastern North America in recent millenniums or extreme drought patterns in sub-Saharan Africa. It’s sobering to recall that the 2002 paper on storminess shows that the epic damage from Vermont’s “flood of record” in 1927, seen in the video above, is a pale shadow of past scouring superfloods in the region. 

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Researching Ancient Climate Change, Peter deMenocal Faced Threat of Pirates

Paleoclimatologist Peter B. deMenocal was on one of the last research vessels to ply the waters off the Horn of Africa before the region was declared off limits to scientists due to the threat posed by Somali pirates—a peril vividly illustrated in this fall’s hit movie, Captain Phillips.

Fortunately deMenocal was aboard a Dutch-flagged vessel. “If we had been flying the American flag I probably wouldn’t be here today,” says the professor and current chair of the Department of Earth and Environmental Sciences and scientist at Columbia’s Lamont-Doherty Earth Observatory.

After receiving faxes about recent attacks in the area, the crew went on high alert, peering with binoculars across the dark waters off the coast of Somalia.

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Were Rivers Flowing across the Sahara During the Last Interglacial? Implications for Human Migration through Africa (with formal correction)

  • Tom J. Coulthard, Jorge A. Ramirez, Nick Barton, Mike Rogerson and Tim Brücher

“Human migration north through Africa is contentious. This paper uses a novel palaeohydrological and hydraulic modelling approach to test the hypothesis that under wetter climates c.100,000 years ago major river systems ran north across the Sahara to the Mediterranean, creating viable migration routes. We confirm that three of these now buried palaeo river systems could have been active at the key time of human migration across the Sahara. Unexpectedly, it is the most western of these three rivers, the Irharhar river, that represents the most likely route for human migration. The Irharhar river flows directly south to north, uniquely linking the mountain areas experiencing monsoon climates at these times to temperate Mediterranean environments where food and resources would have been abundant. The findings have major implications for our understanding of how humans migrated north through Africa, for the first time providing a quantitative perspective on the probabilities that these routes were viable for human habitation at these times” (read more/open access).

(Open access source: PLoS ONE 8(9): e7483, 2013)

Patterns, processes, and impacts of abrupt climate change in a warm world: the past 11,700 years

Shuman, B., 2012: “Patterns, processes, and impacts of abrupt climate change in a warm world: the past 11,700 years.” Wiley Interdisciplinary Reviews: Climate Change, doi: 10.1002/wcc.152.

Abrupt environmental changes punctuated the warm Holocene epoch (the past ~11,700 years), and studies of these episodes can provide insight into the dynamics that produce rapid climate changes, as well as their ecologic, hydrologic, and geomorphic impacts. This review considers the processes that generated warm world abrupt changes and their landscape and resource effects, including nonlinear climate system interactions, as well as the possibility that large climate variability can linearly produce apparent ‘state shifts.’ Representative examples of Holocene changes illustrate processes that could produce future changes, including (1) rapid changes in ice sheets, such as by ca 8200 years before AD 1950, (2) shifts in the behavior of the El Nino-Southern Oscillation (e.g., at ca 5600 years before AD 1950) and Atlantic Meridional Overturning Circulation (e.g., at ca 2700 years before AD 1950), and (3) land–atmosphere feedbacks, such as were possible in North Africa in the mid-Holocene. These case examples, drawn primarily from the Northern Hemisphere, also reveal the dynamics that generate the types of climate change impacts that would be particularly evident to individuals and societies, such as rapid tree species declines (observed to have taken place within as little time as 6–40 years) and persistent shifts in the regional availability of water. Holocene changes also demonstrate that even progressive climate change can produce important abrupt impacts; that increased rates of background climate forcing may increase the frequency of abrupt responses; and that impacts may well depend upon the particular sequence of changes.

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Fifty-million-year-old fossil beetles that fed only on palm seeds are giving Simon Fraser University biologists Bruce Archibald and Rolf Mathewes new information about ancient climates.

According to their research, published online this week in The Proceedings of the National Academy of Sciences, these fossil beetles indicate that during a period of global warming in the geological past, there were mild, frost-free winters extended even in the uplands of ancient western North America.

Working with co-authors Geoffrey Morse of the University of San Diego, California, and David Greenwood of Manitoba’s Brandon University, researchers used fossil beetles to determine winter temperatures where they couldn’t place a thermometer—in the 50-million-year-old uplands of British Columbia and Washington.

The key to their study was finding a particular group of beetles that only feed on palms.

"The natural distribution of palms is limited today to regions without significant frost days, which their seeds and seedlings can’t survive," Archibald explains. "A cooler upland with palms indicates a specific climate type, where a temperate average yearly temperature—rather like Vancouver today—had warmer winters where palms can complete their lifecycles."

But since detecting palm fossils is difficult, the research duo developed a new technique—they used the beetle fossils to test for the palms’ presence. Read More.

Today, all of the West’s great rivers are dammed, and hardly a drop of the flowing surface water remains unmanaged or uncontrolled. This new norm is insidious: the population has a collective idea of abundant water for consumption, despite what the region’s forests and waterways indicate. Too few of the region’s inhabitants notice the connections between dying forests, drying riverbeds, shrinking lakes and reservoir, and the creeping drought. Water continues to flow through the taps, swimming pools are full, and vegetables are abundant and gleaning on the supermarket shelves. But we should not have to wait until the reservoirs run dry to realize how tenuous our engineered control of the regions water is in face of drought or massive floods. Engineered water management was an aid to building a large century of benign, moderately wet times. It is most certainly not likely to sustain what is now an engorged, vastly overgrown modern society.
—  The West without Water: What past floods, droughts and other climatic clues tell us about tomorrow By B. Lynn Ingram, Frances Malamud-Roam
The oldest ice core: Finding a 1.5 million-year record of Earth's climate

From Phys.org

" This shows Antarctic locations (in bright blue) where 1.5 million years old ice could exist. The figure is modified from Van Liefferinge and Pattyn (Climate of the Past, 2013). Credit: Van Liefferinge and Pattyn

(Phys.org) —How far into the past can ice-core records go? Scientists have now identified regions in Antarctica they say could store information about Earth’s climate and greenhouse gases extending as far back as 1.5 million years, almost twice as old as the oldest ice core drilled to date. The results are published today in Climate of the Past, an open access journal of the European Geosciences Union (EGU).

By studying the past climate, scientists can understand better how temperature responds to changes in greenhouse-gas concentrations in the atmosphere. This, in turn, allows them to make better predictions about how climate will change in the future.

"Ice cores contain little air bubbles and, thus, represent the only direct archive of the composition of the past atmosphere," says Hubertus Fischer, an experimental climate physics professor at the University of Bern in Switzerland and lead author of the study. A 3.2-km-long ice core drilled almost a decade ago at Dome Concordia (Dome C) in Antarctica revealed 800,000 years of climate history, showing that greenhouse gases and temperature have mostly moved in lockstep. Now, an international team of scientists wants to know what happened before that.

At the root of their quest is a climate transition that marine-sediment studies reveal happened some 1.2 million years to 900,000 years ago. “The Mid Pleistocene Transition is a most important and enigmatic time interval in the more recent climate history of our planet,” says Fischer. The Earth’s climate naturally varies between times of warming and periods of extreme cooling (ice ages) over thousands of years. Before the transition, the period of variation was about 41 thousand years while afterwards it became 100 thousand years. “The reason for this change is not known.”

Climate scientists suspect greenhouse gases played a role in forcing this transition, but they need to drill into the ice to confirm their suspicions. “The information on greenhouse-gas concentrations at that time can only be gained from an Antarctic ice core covering the last 1.5 million years. Such an ice core does not exist yet, but ice of that age should be in principle hidden in the Antarctic ice sheet.”

As snow falls and settles on the surface of an ice sheet, it is compacted by the weight of new snow falling on top of it and is transformed into solid glacier ice over thousands of years. The weight of the upper layers of the ice sheet causes the deep ice to spread, causing the annual ice layers to become thinner and thinner with depth. This produces very old ice at depths close to the bedrock.

However, drilling deeper to collect a longer ice core does not necessarily mean finding a core that extends further into the past. “If the ice thickness is too high the old ice at the bottom is getting so warm by geothermal heating that it is melted away,” Fischer explains. “This is what happens at Dome C and limits its age to 800,000 years.”

To complicate matters further, horizontal movements of the ice above the bedrock can disturb the bottommost ice, causing its annual layers to mix up.

"To constrain the possible locations where such 1.5 million-year old – and in terms of its layering undisturbed – ice could be found in Antarctica, we compiled the available data on climate and ice conditions in the Antarctic and used a simple ice and heat flow model to locate larger areas where such old ice may exist," explains co-author Eric Wolff of the British Antarctic Survey, now at the University of Cambridge.

The team concluded that 1.5 million-year old ice should still exist at the bottom of East Antarctica in regions close to the major Domes, the highest points on the ice sheet, and near the South Pole, as described in the new Climate of the Past study. These results confirm those of another study, also recently published in Climate of the Past.

Crucially, they also found that an ice core extending that far into the past should be between 2.4 and 3-km long, shorter than the 800,000-year-old core drilled in the previous expedition.

The next step is to survey the identified drill sites to measure the ice thickness and temperature at the bottom of the ice sheet before selecting a final drill location.

"A deep drilling project in Antarctica could commence within the next 3-5 years," Fischer states. "This time would also be needed to plan the drilling logistically and create the funding for such an exciting large-scale international research project, which would cost around 50 million Euros."

Original - link

More information: Fischer, H. et al.: Where to find 1.5 million yr old ice for the IPICS ‘Oldest-Ice’ ice core, Clim. Past, 9, 2489-2505, DOI: 10.5194/cp-9-2489-2013 , 2013”

More on Paleoclimatology and Core Samples here