Sentences with phrase «by glaciation»

It is by definition (more accurately, by the laws of physics) autocorrelated over some period of time which could be anything up to 35 million years even going by the change caused by the glaciation of Antarctica.

On the other hand, if some of the anthropogenic aerosols act as ice nuclei, supercooled clouds could be converted into ice clouds by the glaciation indirect effect (Lohmann, 2002), resulting in more efficient precipitation formation.

Iodine Source: Seaweed, milk from cows grazed on iodine - rich coastal soil Effects of deficiency: Blindness, mental impairment, goiter Who's at risk: People living in mountainous areas (the Rockies, the Alps, and the Andes), where iodine has been washed away by glaciation and flooding, or in lowland regions far from the oceans (Central Africa and Eastern Europe) Fortification options: Salt Estimated millions of people affected: 740

They suggest that the two raven types may have been geographically isolated, possibly by glaciation, and are now remerging.

There is evidence that ocean circulation patterns are disrupted by glaciations.

The remote and hostile Southern Ocean is home to a diverse and rich community of life that thrives in an environment dominated by glaciations and strong currents.

Not exact matches

Linked by a single root system, Pando consists of tens of thousands of genetically identical trees, cloned from a sprout that emerged after the last glaciation in southern Utah, roughly 13,000 years ago.

Puzzled by types of mollusc that abruptly disappeared from the British fossil record, apparently in response to a glaciation, only to reappear 2 million years later completely unchanged, he asked of Darwin: «Be so good as to explain all this in your next letter.»

We do estimate that an area of hydrocarbon reserves twice the size of Russia was directly influenced by ice sheets during past glaciation.

While the first of the glaciations that the team studied was probably triggered by nonvascular plants such as mosses and liverworts, the second ice age — the one that began around 445 million years ago — may have been brought on by the rise and spread of vascular plants.

So, Retallack suggests, colonization of the land by vascular and nonvascular plants together may help explain the massive drawdown of CO2 that triggered the most recent and stronger of the two major glaciations that Lenton and his colleagues studied.

«In addition, this early phase of evolutionary divergence appears to have preceded the extreme climate changes that led to Snowball Earth, a period marked by severe long - term global glaciation that lasted from about 720 to 635 million years ago,» Dohrmann says.

They have not had the remaking influences of fairly recent glaciation and sedimentation, followed by the biological colonization typical of many rich lands in more temperate zones.

One theory is that the glaciation was triggered by the evolution of large cells, and possibly also multicellular organisms, that sank to the seabed after dying.

The crisp pictures released today show mesas and canyons, sinuous valleys apparently carved by running water, features that hint at former glaciation, and «waterfalls» of dust at the slope of a volcanic caldera.

There seem to have been two distinct Cryogenian ice ages: the so - called Sturtian glaciation between 750 and 700 million years ago, followed by the Varanger (or Marinoan) glaciation, 660 to 635 million years ago.

The late Proterozoic — the time period beginning less than a billion years ago following this remarkable chapter of sustained low levels of oxygen — was strikingly different, marked by extreme climatic events manifest in global - scale glaciation, indications of at least intervals of modern - like oxygen abundances, and the emergence and diversification of the earliest animals.

Michael Mann, a meteorology professor at Penn State who was not involved with the study, said it's «speculative» but «plausible» that global climate models have been underestimating climate sensitivity by assuming too much cloud glaciation.

The current global cycle of glaciation dates to this period and might have been triggered by a transformation of the world's ocean currents, which a slender rib of land separating Atlantic and Pacific would naturally explain.

By matching these isotope ratios to the astronomical cycle — Earth's orbit oscillates between an elliptical and circular path on a roughly 400,000 - year cycle — the researchers found that patterns of glaciation and ice retreat followed the eccentricity of our planet's orbitthey report in the December 22 Science.

Nearby Mauna Loa probably also was glaciated, but evidence of its glaciation has since been destroyed by volcanic eruptions.

There is also an idea that mountain glaciers, and repeated continental glaciation and deglaciation, may actually enhance chemical weathering by their mechanical weathering, even though the cold climate generally inhibits it.

«Hotspot of biodiversity as a characteristic of the Balkans was put forward by biogeographers to indicate that most of the plant and animal species that repopulated the continent after glaciations came from the Balkans,» Roksandic explained.

[10] Earlier still, a 200 - million year period of intermittent, widespread glaciation extending close to the equator (Snowball Earth) appears to have been ended suddenly, about 550 million years ago, by a colossal volcanic outgassing which raised the CO2 concentration of the atmosphere abruptly to 12 percent, about 350 times modern levels, causing extreme greenhouse conditions and carbonate deposition as limestone at the rate of about 1 mm per day.

During glaciation, water was taken from the oceans to form the ice at high latitudes, thus global sea level drops by about 120 meters, exposing the continental shelves and forming land - bridges between land - masses for animals to migrate.

This caused weathering to decrease by about 4 times globally, allowing CO2 and temperatures to recover, terminating the glaciation,» Pogge von Strandmann said.

Ice ages can be further divided by location and time; for example, the names Riss (180,000 — 130,000 years bp) and Würm (70,000 — 10,000 years bp) refer specifically to glaciation in the Alpine region.

The glaciation was favored by an interval when the Earth's orbit favored cool summers but Oxygen isotope ratio cycle marker changes were too large to be explained by Antarctic ice - sheet growth alone indicating an ice age of some size.

Beringia was by no means a tropical paradise for life, but the cold, wind - swept desert was an important ecological refuge for plants and animals when glaciation of the Earth was at its peak.»

In the east of Utrecht lies the Utrechtse Heuvelrug, a chain of hills left as lateral moraine by tongues of glacial ice after the Saline glaciation that preceded the last ice age.

Lesson 3 - Processes of Glaciation Lesson 4 - Glacial landforms shaped by erosion.

The development of Ambergris Caye is tied to sea level and sea level is controlled by major glaciation.

More recently, Marsh has postulated that the onset of glaciation is also due to variations in solar activity, but does not follow the Milankovitch cycles as described by B&L.

It is to be noted here that there is no necessary contradiction between forecast expectations of (a) some renewed (or continuation of) slight cooling of world climate for a few decades to come, e.g., from volcanic or solar activity variations; (b) an abrupt warming due to the effect of increasing carbon dioxide, lasting some centuries until fossil fuels are exhausted and a while thereafter; and this followed in turn by (c) a glaciation lasting (like the previous ones) for many thousands of years.»

Abstract:... beneath portions of the northeastern Laurentide Ice Sheet, characterized by cold - based glaciation, sediment sequences representing multiple interglaciations have been preserved within extant lake basins.

The paper in Ambio (1997) shows in Fig 2 the entrance into glaciation starting now if CO2 is 210 ppmv, but the threshold in our model for entering into glaciation has been indicated many times to be 240 ppmv (see paper by Loutre and Berger cited by Tzedakis et al., and the papers Berger and Loutre in Science 2002, Berger et al. in Surveys in Geophysics 2003).

Ike, if you haven't read Ruddiman's, «Plows, Plagues & Petroleum», it's been out in paperback fro a few months, and bears on this, i.e., evidence of start of lonnnnng glaciation process possibly aborted by early CO2 & CH4.

I remind you of the paper by Kukla et al and the special issue of Quaternary Research in 1972, concluding that based on the comparison with the other interglacials we will enter soon in glaciation (see the introduction of our papers to have a summary of that story).

Here we propose that increasing variablility within the past million yearsmay indicate that the climate system was approaching a second climate bifurcation point, after which it would transition again to a new stable state characterized by permanent mid-latitude Northern Hemisphere glaciation.

The paper was motivated by the idea that the timing of Antarctic glacial movements was set by sea - level changes that reflected Northern Hemisphere glaciation.

Ice age - An ice age or glacial period is characterized by a long - term reduction in the temperature of the Earth's climate, resulting in growth of continental ice sheets and mountain glaciers (glaciation).

The degradation of the extrapolar glaciation of the Earth will be apparent in rising ocean level already by the year 2050, and there will be a drastic rise of the ocean thereafter caused by the deglaciation - derived runoff (see Table 11).

Evidence of previous glaciations is erased by subsequent glaciations and ongoing erosion.

Glaciations in the Ordovician and Devonian were apparently accompanied by high [compared with now] levels of atmospheric CO2.

Actually, the high CO2 concentrations during large glaciations in the paleozoic were discovered by scientists trying to understand how the earth became deglaciated after essentially freezing over.

I.e., The glaciations were not initiated by CO2, but they were exacerbated by feedbacks that increased CO2.

It was developed by scientists at CAGE — Centre for Arctic Gas Hydrate Environment and Climate, and shows that seafloor off Western Svalbard was covered by a large ice sheet during the last glaciation.

Fossil fuel consumption rates will slowly diminish over the coming decades as fossil fuels are gradually depleted, and the resultant atmospheric and oceanic CO2 is predicted by IPCC modelers to END glaciation cycles and thus, to open much of Canada and Siberia to greatly improved agriculture and forestry.

The concept of «snowball earth» is based on interpretation of some geological formations as evidence of glaciation — an interpretation that is not shared by a number of Canadian geologists specializing in glaciation (an important phenomenon in Canadian geology).

C: Datasets suggesting a drying environment at 2.5 Ma, shown by λ 18O from benthic foraminifera, a proxy for global temperature, smoothed with a Gaussian window of 200 ky; eustatic sea level; and magnetic susceptibility, a proxy for ice rafted debris and Northern Hemisphere glaciation.