You are looking at 1-20 of 61 entries  for:

  • All: Ice-rafting events x
clear all

View:

Overview

Ice-rafting events

Glacial surges in sudden changes of climate Calved from greenland's glaciers, icebergs migrate south in spring and early summer, carried by the subzero ...

Ice-rafting events

Ice-rafting events  

Magic Universe: A Grand Tour of Modern Science

...their hunch that ice-rafting events continued after the ice age. They were much less conspicuous in terms of the amount of rafted material, but they had about the same rhythm, and their effects on climate were not negligible. Datings were approximate, but it turned out that the most recent ice-rafting events were about 350 and 600 years ago, during the period long known to historians of climate as the Little Ice Age. A big reduction in rafted debris around 800 years ago fitted with a well-known Medieval Warm Period. Ice rafting 1700 years ago coincided...

Ice-rafting events

Ice-rafting events  

Reference type:
Overview Page
Glacial surges in sudden changes of climateCalved from greenland's glaciers, icebergs migrate south in spring and early summer, carried by the subzero Labrador Current. When they meet the warm ...
Heinrich event

Heinrich event   Quick reference

A Dictionary of Weather (2 ed.)

Reference type:
Subject Reference
Current Version:
2008

...event A period of increased iceberg calving from the Laurentide (North American) ice sheet into the North Atlantic during the last ice age . At least six of these events have been recognized from the increased frequency of large-sized, ice-rafted debris deposited in marine sediments. The greatly increased input of light fresh water to the surface layer probably caused major disruptions to oceanic circulation, specifically to the Great Ocean Conveyor Belt , with consequent effects upon the climate in the northern hemisphere, and particularly in areas...

Heinrich Events

Heinrich Events   Reference library

The Oxford Companion to Global Change

Reference type:
Subject Reference
Current Version:
2009

...contain iceberg-rafted detritus, have a high carbonate content that is probably derived from the source region of Paleozoic limestones and dolomites in eastern Canada and possibly northwestern Greenland ( Bond et al., 1992 ). This suggests that the lithic sediments of the Heinrich events were excavated by the Hudson Strait ice stream, which drained a large part of the former Laurentide ice sheet. Rapid fluctuation in this ice stream not only produced the sudden Heinrich events (of which there have been 6 over 60 thousand years) but also led to the creation of...

Bond oscillation

Bond oscillation   Quick reference

A Dictionary of Geography (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...oscillation ( Bond cycles, Bond event ) Bond et al. (1997) Science 278: 1257 established quasi-periodic ( c .1500 years) climate fluctuations during the Holocene. They related ice-rafted debris (IRD) with the slowdown of the Atlantic thermohaline circulation (THC) and, later, to variations in solar radiation, as the IRD fluctuations were coherent with the production rates of cosmogenic nuclides of 14 C and 10 Be ( Bond et al. (2001) Science 294: 2130 ). Therefore, Bond cycles suggest that solar radiation must have had a marked influence on...

Greenland ice cores

Greenland ice cores   Reference library

The Oxford Companion to the Earth

Reference type:
Subject Reference
Current Version:
2003

...contain ice-rafted debris from Canada and low numbers of foraminifera, which reflect low oceanic productivity. The Heinrich events seem to be spaced at intervals of about 10 000 years and occur during the coldest of a series of Dansgaard–Oeschger phases. The apparent regularity of these cycles may suggest a link with the Earth's precessional cycle. However, others argue it might be due to the internal dynamics of the Laurentide ice sheet, alternately building up and discharging large amounts of ice. The fact that similar and synchronous discharge events have now...

Cryosphere

Cryosphere   Reference library

Magic Universe: A Grand Tour of Modern Science

Reference type:
Subject Reference
Current Version:
2009
Subject:
Science and technology, History of Science
Length:
2,865 words

...stones and other debris in hills called terminal moraines, which remain when the glaciers retreat. Moraines have helped to chart the extent of the ice during past ice ages. They also preserve a record of repeated advances and retreats of the mountain glaciers during the past 10,000 years. These may be related to cooling events seen in outbursts of icebergs and sea-ice in the North Atlantic, called ice-rafting events, which in turn seem to be linked to changes in the Sun's behaviour. The confusing and sometimes contradictory impressions of the cryosphere are...

Glaciation

Glaciation   Reference library

Encyclopedia of Global Change

Reference type:
Subject Reference
Current Version:
2005
Subject:
Science and technology, Environmental Science, Social sciences, Environment
Length:
5,712 words
Illustration(s):
5

...Dryas, ca. 13,000–11,500 years ago) are reflected in ocean sediments. The so-called Heinrich Events, consisting of abundant ice-rafted debris in the North Atlantic, record episodes in the glacial history of the Quaternary North American ice sheet. Also, the thermally generated North Atlantic Deep Water appears to have switched on and off during the Neogene (25 million to 1.8 million years ago). The “Little Ice Age,” including advances of alpine glaciers, occurred during our present interglacial between about 450 and 150 years ago. At present, the Earth is...

glacial sediments

glacial sediments   Reference library

The Oxford Companion to the Earth

Reference type:
Subject Reference
Current Version:
2003
Subject:
Science and technology, Earth Sciences and Geography
Length:
1,203 words
Illustration(s):
1

...a varve ). The silty layers are in some instances graded or multiple owing to deposition by either single or repeated events. The darker clay layers may also show grading. The couplets are produced by the introduction and deposition of silt during summer melting followed by slow deposition of fine suspended clay during winter, often under an ice cover. The continental shelves surrounding glaciers are cloaked with till deposited by ice rafting from the adjacent land. They are commonly cut by erosional surfaces with gravel concentrates produced by...

Sea Ice

Sea Ice   Reference library

Encyclopedia of Global Change

Reference type:
Subject Reference
Current Version:
2005
Subject:
Science and technology, Environmental Science, Social sciences, Environment
Length:
4,223 words
Illustration(s):
5

...a pancake. Deeper inside the ice edge, sheltered from waves, the pancakes freeze together in groups that finally coalesce to form a continuous ice sheet. With the open water surface cut off, the growth rate drops to a low level and the ultimate sheet thickness at winter's end may be only a few centimeters more than the thickness of the constituent pancakes. Such ice is called consolidated pancake ice and has a rough, jagged bottom morphology, unlike congelation ice. Pancakes at the time of consolidation may be rafted or upended, and freeze together in...

Paleoclimate

Paleoclimate   Reference library

The Oxford Companion to Global Change

Reference type:
Subject Reference
Current Version:
2009
Subject:
Science and technology, Environmental Science, Social sciences, Environment
Length:
3,725 words
Illustration(s):
4

...events have been identified in ice-core records: 24 of them have been recognized in the period from 115,000 to 14,000 years ago. [ See Dansgaard-Oeschger Cycles .] The nature and causes of such abrupt climatic fluctuations within glacials have been discussed by Adams et al. ( 1999 ). Some cold snaps, termed Heinrich events ( Andrews , 1998 ), have been identified in ocean-sediment cores through the evidence of debris rafted by icebergs. At least seven Heinrich events occurred between 66,000 and 12,000 years ago. [ See Heinrich Events .]...

Pliocene

Pliocene   Reference library

The Oxford Companion to the Earth

Reference type:
Subject Reference
Current Version:
2003

...Anglia and small patches of sands in southern England. All evidence points to the Pliocene as a time of continuing cooling of world climate, with major pulses of ice-rafted rock debris being released into the North Atlantic. The warm Gulf Stream and the cold Labrador Current were in operation and climate was highly seasonal. About halfway through the Pliocene epoch several important tectonic events occurred. The continuing activity of the African Rift system saw the opening of the Red Sea rift to the point where oceanic crust was generated there for the first...

Carbon cycle

Carbon cycle   Reference library

Magic Universe: A Grand Tour of Modern Science

Reference type:
Subject Reference
Current Version:
2009
Subject:
Science and technology, History of Science
Length:
3,112 words

...the North Atlantic become chilly then? A whole chapter of the climate story concerns that cooling and a series of others like it, which are called ice-rafting events. Their causes were much debated. Dave Keeling thought that changes in the Moon's tides were involved, whilst Gerard Bond of Columbia and his colleagues linked ice rafting to weakening magnetic activity on the Sun. Either way, they were natural events, driving the level of carbon dioxide, not obeying it. Wagner's birch-leaf results on ancient levels of carbon dioxide passed virtually unnoticed by...

Ice Ages

Ice Ages   Reference library

Encyclopedia of Climate and Weather (2 ed.)

Reference type:
Subject Reference
Current Version:
2011
Subject:
Science and technology, Earth Sciences and Geography, Social sciences, Environment
Length:
3,162 words
Illustration(s):
4

...ice sheet can significantly depart from this convention (for the Scandinavian ice sheet, see Svendsen et al., 2004 ). Alpine glaciers in both hemispheres descended by 600 to 1,400 meters elevation depending on the latitude of the mountain ranges ( e.g., Mark et al., 2005 ; Stansell et al., 2007 ; Osipov, 2004 ; Florineth and Schlüchter, 2000 ). In geological terms, this last ice age ended around 8,000 years ago, and much evidence remains intact that allows a fairly detailed reconstruction of events. Pleistocene oscillations between the major ice age...

Pleistocene

Pleistocene   Reference library

Alastair G. Dawson

The Oxford Companion To Archaeology (2 ed.)

Reference type:
Subject Reference
Current Version:
2012
Subject:
Archaeology
Length:
3,019 words

...North American/North Atlantic/European Sector and Comparison with the Geological Record of North America.” Quaternary Science Reviews 4 (1985): 147–187. Shackleton, Nicholas J. “Oxygen Isotopes, Ice Volume and Sea Level.” Quaternary Science Reviews 6 (1987): 183–190. Shackleton, Nicholas J. , et al. “Oxygen Isotope Calibration of the Onset of Ice-Rafting and History of Glaciation in the North Atlantic Region.” Nature 307 (1984): 620–623. Alastair G....

Paleoclimate

Paleoclimate   Reference library

Encyclopedia of Global Change

Reference type:
Subject Reference
Current Version:
2005
Subject:
Science and technology, Environmental Science, Social sciences, Environment
Length:
4,877 words
Illustration(s):
5

...cores through the evidence of iceberg-rafted debris. These have been termed Heinrich events (Andrews, 1998). At least seven Heinrich events occurred between 66,000 and 12,000 years ago. Interglacials In general terms, the Quaternary interglacials, though short-lived, appear to have been essentially similar in their climate, fauna, flora, and landforms to the Holocene interglacial in which we live today. One of the most important characteristics was that they witnessed the rapid retreat and decay of the great ice sheets and saw the replacements of tundra...

Climate change

Climate change   Reference library

Magic Universe: A Grand Tour of Modern Science

Reference type:
Subject Reference
Current Version:
2009
Subject:
Science and technology, History of Science
Length:
3,591 words

...well as the community that believes that greenhouse is a major problem.’ The link between carbon dioxide and climate is further examined in Carbon cycle . For more about ice and climate change , see Cryosphere . Uncertainties about the workings of the ocean appear in Ocean currents . Aspects of the climatic effects of the variable Sun appear in Earthshine and Ice-rafting events . Natural drivers of brief climate change are El Ninõ and Volcanic explosions...

Cores

Cores   Reference library

Encyclopedia of Climate and Weather (2 ed.)

Reference type:
Subject Reference
Current Version:
2011
Subject:
Science and technology, Earth Sciences and Geography, Social sciences, Environment
Length:
4,191 words
Illustration(s):
3

...and temperature also vary as the Earth oscillates between ice age and interglacial conditions, clearly the 18 O isotope record is not a perfect reflection of ice volume. This problem can be partially circumvented by comparing cores from different locations and foraminifera living at different depths in the ocean. Other quantities in an ocean sediment core, including the concentrations of dust (small mineral particles blown from the continents), other terrestrial minerals, pollen, and ice-rafted debris (coarse unsorted rock fragments transported by...

Natural Climate Fluctuations

Natural Climate Fluctuations   Reference library

Encyclopedia of Global Change

Reference type:
Subject Reference
Current Version:
2005
Subject:
Science and technology, Environmental Science, Social sciences, Environment
Length:
6,703 words
Illustration(s):
6

...subsequently been termed Heinrich events (Broecker et al., 1992). The key features of sediment delivery among Heinrich events are the presence of icebergs, meltwater plumes, and massive gravity flows called turbidites . These processes, which are associated with cold events (stadials), produce sediments with a high lithic content, whereas the foraminifera-rich non-Heinrich sediments were deposited during warmer (interstadial) periods. Record of Henirich ice rafting events (H1–H6) in the North Atlantic: (A) ice-rafted sediment derived from land sources;...

Bernal's ladder

Bernal's ladder   Reference library

Magic Universe: A Grand Tour of Modern Science

Reference type:
Subject Reference
Current Version:
2009
Subject:
Science and technology, History of Science
Length:
608 words

...the implications were largely unheeded, was the evidence that the evolution of species plays a significant part in the response of ecosystems to current changes ( see Eco-evolution ). Similarly situated was the role of solar variations in major changes of climate ( see Ice-rafting events ). Grudging acceptance, as achieved on rung 3 of Bernal's ladder, came for the evidence that adult brains continually renew their nerves cells and can reorganize their connections ( see Brain wiring ). A ding-dong argument had raged all through the 20th century, between...

View: