Sentences with phrase «during glacial times»

The increased atmospheric dust load during glacial times is thought to be due to a generally colder and drier atmosphere, which increased the number and strength of dust sources through reduced vegetation cover (28), and reduced washout of suspended particles during transport (7).

By extrapolating from its radiative forcing in the current climate, we estimate that dust reduces precipitation during glacial times by as much as half the reduction due to the colder climate alone.

This method tries to maximize using pure observations to find the temperature change and the forcing (you might need a model to constrain some of the forcings, but there's a lot of uncertainty about how the surface and atmospheric albedo changed during glacial times... a lot of studies only look at dust and not other aerosols, there is a lot of uncertainty about vegetation change, etc).

One explanation (ix) conceived in the 1980s invokes more stratification, less upwelling of carbon and nutrient - rich waters to the surface of the Southern Ocean and increased carbon storage at depth during glacial times.

Dr. Archer has worked on the ongoing mystery of the low atmospheric CO2 concentration during glacial time 20,000 years ago, and on the fate of fossil fuel CO2 on geologic time scales in the future, and its impact on future ice age cycles, ocean methane hydrate decomposition, and coral reefs.

The climate record obtained from two long Greenland ice cores reveals several brief climate oscillations during glacial time.

75 During glacial time (and perhaps during the cold flips as well), the tropics were less wet than now — but some desert regions such as Nevada were less dry.

Not exact matches

The last glacial period spanned from 110,000 to 10,000 years ago; during that time the Earth was colder and glaciers covered significantly more land.

She analyzed samples that had broken off the formations to see what periods of time during a period called the last glacial period had high rainfall, and which had low rainfall.

These may be submerged ancient shorelines cut during times of lower sea level, «the most recent of which occurred during the last glacial period, which ended about 19,000 years ago,» Chaytor said.

«Although this period is around the late glacial maximum, there is a blip at 23,000 years during which time it was milder.»

But for the other half of the picture — what happened in the oceans during that time — there is only a relatively short record extending back about 20,000 years to the last glacial cycle.

«Neanderthals were almost certainly making fire during the last glacial period,» says Sorensen, referring to a time about 100,000 to 35,000 years ago.

Blunier, T. and E. J. Brook, 2001: Timing of millennial - scale climate change in Antarctica and Greenland during the last glacial period.

Vetoretti and Peltier (2004) found that glacial inceptions can be caused either by a strong obliquity forcing or by a combination of eccentricity - precession forcing and low CO2 values, which is in line with results from Berger and Loutre (2001) who found that CO2 is important during times like the MIS - 11, when the insolation variations are too small to drive glacial - interglacial cycles.

Melting of glacial ice could play an important role in maintaining water security during times of drought or similar climate extremes, the committee noted.

For example, atmospheric carbon dioxide grew by approximately 30 % during the transition from the most recent cold glacial period, about 20,000 years ago, to the current warm interglacial period; the corresponding rate of decrease in surface ocean pH, driven by geological processes, was approximately 50 times slower than the current rate driven largely by fossil fuel burning.

The vertical movements that occurred during retreat of the ice sheets in late glacial time are very much more complex than during postglacial time.

Kelly and Lowell (2009) say that «subsequent to late - glacial or early Holocene time, most local glaciers were smaller than at present or may have disappeared completely during the Holocene Thermal Maximum,»

What is known is that during the period called Little Ice Age, global glacial were advancing, and starting around 1850, instead advancing global glacier became retreating, this trend of glacial retreat continues to the present time, but not all glaciers adding during the Little Ice Age have not yet melted.

The demonstration that D - O events are globally distributed and that they operated during previous glacial periods has led to extensive research into the relative hemispheric timing and causes of these events.

Meanwhile, this biomarker approach has been used successfully in many studies dealing with the reconstruction of Arctic sea ice history during the last glacial to Holocene time interval, i.e., the last about 30 ka31, 32,33,34,35,36,37.

This type of behavior is especially evident during transitions from glacial to interglacial conditions, when climate is affected by a wide variety of time - varying influences and is relatively unstable.

Dansgaard — Oeschger events (often abbreviated D — O events) are rapid climate fluctuations that occurred 25 times during the last glacial period.

Last Glacial Maximum (LGM)- The Last Glacial Maximum refers to the time of maximum extent of the ice sheets during the last glaciation, approximately 21 ka.

As there is a lot of talk of the see - saw mechanism (in decadal - centurial scale) during the glacial terminations, might this effect be noticeable also in shorter periods of time?

This fossilized coral reef was alive about 20,000 years ago, during the height of the last glacial period, a time when Earth was around 9 degrees Fahrenheit (5 degrees Celsius) cooler than it is now, and the city of Chicago was buried beneath an ice sheet almost 2 miles (3 kilometers) thick.

Even on the Siberian continental margin, where water temperatures are colder than the global average, and where the sediment column retains the cold imprint from its exposure to the atmosphere during the last glacial time 20,000 years ago, any methane hydrate must be buried under at least 200 m of water or sediment.

These rapid changes in atmospheric CO2 and CH4 concentrations are also recorded during the Heinrich Stadials of MIS 3, demonstrating an important mechanism that operates on centennial time scales during the glacial and deglaciation, which may point to important thresholds in the global carbon cycle.

«For micro-organisims which have generation times of a few days, adaptation may happen during the next 100 years or so as the ocean continues to acidify to critical levels,» explained the researcher from the IFM - Geomar centre, braving glacial winds in a bright yellow padded windbreaker and a woolen hat.

Related Volcanoes, Tree Rings, and Climate Models: This is how science works Fossil Focus: Using Plant Fossils to Understand Past Climates and Environments Atmospheric oxygen over Phanerozoic time Coupled carbon isotopic and sedimentological records from the Permian system of eastern Australia reveal the response of atmospheric carbon dioxide to glacial growth and decay during the late Palaeozoic Ice Age

«The Laurentide Ice Sheet was a massive sheet of ice that covered hundreds of thousands of square miles, including most of Canada and a large portion of the northern United States, multiple times during Quaternary glacial epochs.

Imputities are a main problem in Greenland ice cores where a mix of seasalt / carbonate and acidic dust from Icelandic volcanoes can produce CO2 in situ, but is less of interest in deep inland Antarctic ice cores, except during the deepest times of glacials, when far more dust is deposited.

``... expect to see changes in pH that are three times greater and 100 times faster than those experienced during the transitions from glacial to interglacial periods.

Actually, by the time you approach 200ppmv for CO2, you have already reached the break point in the curve, beyond which additional CO2 has much less impact on the RF — and this is close to the glacial value — suggesting that CO2 changes do not drive the glacial cycles (CO2 changes are supposed to amplify T rise during deglaciation, but there is scant evidence for this and the assumption that it did also underlay the IPCC belief — and a great many references in academic papers give a T degrees C per ppmv CO2 without stating over which range of concentrations this is meant to apply.

There has been no average or typical state for global climate during Pleistocene and Holocene times; the Earth system has been in continual flux between interglacial and glacial patterns.