when was the older dryas

What caused the Oldest Dryas?

Fauna. Species were mainly Arctic but during the Glacial Maximum, the warmer weather species had withdrawn into refugia and began to repopulate Europe in the Oldest Dryas.

When did the Younger Dryas end?

about 11,500 years agoThis near-glacial period is called the Younger Dryas, named after a flower (Dryas octopetala) that grows in cold conditions and that became common in Europe during this time. The end of the Younger Dryas, about 11,500 years ago, was par- ticularly abrupt.

Why did the Younger Dryas end?

Abrupt climate change The change to glacial conditions at the onset of the Younger Dryas in the higher latitudes of the Northern Hemisphere, between 12,900 and 11,500 calibrated years BP, has been argued to have been quite abrupt.

What triggered the Younger Dryas?

Conventional geologic wisdom blames the Younger Dryas on the failure of glacial ice dams holding back huge lakes in central North America and the sudden, massive blast of freshwater they released into the north Atlantic. This freshwater influx shut down ocean circulation and ended up cooling the climate.

Is a new ice age possible?

Will we enter into a new ice age? No. Even if the amount of radiation coming from the Sun were to decrease as it has before, it would not significantly affect the global warming coming from long-lived, human-emitted greenhouse gases.

When was the last Ice Age?

The Last Glacial Period (LGP), also known colloquially as the last ice age or simply ice age, occurred from the end of the Eemian to the end of the Younger Dryas, encompassing the period c. 115,000 – c. 11,700 years ago.

Are we in an ice age?

We are in an interglacial period right now. It began at the end of the last glacial period, about 10,000 years ago. Scientists are still working to understand what causes ice ages. One important factor is the amount of light Earth receives from the Sun.

What ended the last Ice Age?

New University of Melbourne research has revealed that ice ages over the last million years ended when the tilt angle of the Earth's axis was approaching higher values.

When did the last Ice Age end?

The last glacial period began about 100,000 years ago and lasted until 25,000 years ago.

What was unique about the Younger Dryas?

The Younger Dryas was characterized by cooler average temperatures that returned parts of Europe and North America to ice age conditions. The onset of the Younger Dryas took less than 100 years, and the period persisted for roughly 1,300 years.

What year did climate change begin?

The instrumental temperature record shows the signal of rising temperatures emerged in the tropical ocean in about the 1950s. Today's study uses the extra information captured in the proxy record to trace the start of the warming back a full 120 years, to the 1830s.

When was the Little Ice Age?

1303Little Ice Age / Start date

Was the Younger Dryas triggered by a flood?

It is widely believed that this cold event was triggered by a flood of fresh water that poured into the northern Atlantic (1) and disrupted the thermohaline ocean circulation (2).

How long ago was the Loch Lomond Stadial?

The Younger Dryas / Loch Lomond Stadial was an abrupt period of renewed cooling between 12,900 and 11,700 years ago and has long been associated with the regrowth of glaciers in much of upland Britain.

Why did the Loch Lomond Stadial happen?

A sudden cooling of the atmosphere in the Northern Hemisphere happened around 12,900 years ago, called the Younger Dryas, which caused the ice caps to expand and form the Loch Lomond Stadial ice masses shown in the map below3.

What caused the Bolling allerod?

Here we show that the release of heat from warm waters in the deep North Atlantic Ocean probably triggered the Bølling-Allerød warming and reinvigoration of the Atlantic meridional overturning circulation.

What is the oldest dryas?

The Oldest Dryas is a biostratigraphic subdivision layer corresponding to a relatively abrupt climatic cooling event, or stadial, which occurred during the last glacial retreat.

What is the stratigraphic layer of Dryas?

As with the Younger and Older Dryas events, the stratigraphic layer is marked by abundance of the pollen and other remains of Dryas octopetala, an indicator species that colonizes arctic-alpine regions. In the Alps, the Oldest Dryas corresponds to the Gschnitz stadial of the Würm glaciation.

What is the oldest dryas?

Zone I-a, Oldest Dryas. The sedimentation of white laminated calcareous gyttja on sterile blue–grey clay started during the Oldest Dryas. The pollen concentrations of the white gyttja are very low (<200 grains/mL). In the relative pollen diagrams, the Oldest Dryas is dominated by non-arboreal pollen (mainly Artemisia, Cyperaceae, Helianthemum, Poaceae). The low pollen concentrations indicate that pollen precipitation was mainly the result of long-distance transport. Biomass production in and around the Gasserplatz lake was very low, considering the relatively high δ 13 C values.

Why did the Dryas occur?

The cause of the Younger Dryas is thought to be shutdown of the North Atlantic thermohaline circulation due to an outpouring of glacial meltwater from North America (see Chapter 2 ). As climate warmed and continental ice sheets melted, large quantities of freshwater accumulated in what are now the Great Lakes of the United States and Canada. Ice blocked drainage of these lakes for many years. Finally, the blockage was breached, and huge amounts of freshwater gushed out the St. Lawrence seaway and into the North Atlantic. There, the freshwater diluted the salinity of the Gulf Stream, preventing it from sinking. This disrupted the thermohaline circulation and shut down the Gulf Stream. The heat pumped from the equator by the Gulf Stream suddenly ceased to arrive in the North Atlantic, resulting in a rapid cooling. When the freshwater pulse stopped, the thermohaline circulation turned back on and the region rapidly resumed warming.

What are the bio- and isotope stratigraphies of the Late Glacial on the Swiss Plateau?

Ecologically, the most remarkable change from the shrub–tundra in the Oldest Dryas to a juniper–birch forest in the early Bølling (i.e., a shift in dominance from dwarf birches to tree birches) coincides with the rapid shift in oxygen isotopes of at least 3 around 14 500 cal yr BP. It is accompanied by changes in the assemblages of insects (chironomids, Chaoborus, Coleoptera, and Trichoptera) and Cladocera as well as a change in abundances among mollusks. The subdivision of the Oldest Dryas based on pollen and plant macrofossils (see text for details) is also reflected in the biostratigraphies of the invertebrates: First occurrences coincide with the stepwise development of the vegetation. The rapid cooling at the beginning and the rapid warming at the end of the Younger Dryas are recorded in the oxygen isotope ratios and all biostratigraphies.

How did the temperature change during the Younger Dryas?

The temperature changes during the Younger Dryas were dramatic . In Greenland, the swings at the opening and closing of the cold snap have been estimated to be more than 10 °C in a century. In Britain, a warming of 10–15 °C has been estimated for the end of the cold snap. Temperature swings in other areas of the world were less, but there is evidence that the Younger Dryas was a global phenomenon.

Where is Biscaye Peat Bog?

Biscaye peat bog (400 m, Lourdes) in the depression immediately behind the frontal Würmian moraine formed of unweathered material and related to the lowest terrace. It has provided a pollen sequence from the last 45,000 years and demonstrates that the glacial maximum dates from the Early Würmian and that the deglaciation began in the Lourdes basin at 29,500 B.P. ( Mardones & Jalut, 1983 ).

Is the Younger Dryas oscillation a terrestrial or terrestrial event?

The approach taken here is one of many possible approaches to this topic: namely, a terrestrial geological one. This is, however, adequate since the original identification, naming, and documentation of the Younger Dryas event was carried out by Scandinavian Quaternary terrestrial geologists and paleobotanists. In addition, the Younger Dryas is still probably best manifested by an often distinct lithologic change in lacustrine records of western Europe ( Fig. 1 ).

Who published the pollen diagram of late glacial lake deposits in the Alpine region?

Similar oscillations in pollen diagrams of Late Glacial lake deposits in the Alpine region have been published by Bortenschlager (1984).

What is the Older Dryas?

In the Greenland oxygen isotope record, the Older Dryas appears as a downward peak establishing a small, low-intensity gap between the Bølling and the Allerød. This configuration presents a difficulty in estimating its time, as it is more of a point than a segment. But which point, and how long a segment should be assigned? The segment is small enough to escape the resolution of most C-14 series; i.e., the points are not close enough together to find it.

When was the Dryas period?

The Older Dryas was a stadial (cold) period between the Bølling and Allerød interstadials (warmer phases) approximately 14,000 years ago ( BP ), towards the end of the Pleistocene epoch. Its age is not well defined, with estimates varying by 400 years, but its duration is agreed to have been around two centuries. The gradual warming since the last glacial maximum 27-24,000 years BP has been interrupted by two cold spells, the Older Dryas having been followed by the Younger Dryas (c. 12,900-11,650 BP). In northern Scotland the glaciers were thicker and deeper during the Older than the succeeding Younger Dryas, and there is no evidence of human occupation of Britain. In north-west Europe an earlier Oldest Dryas is also recognised. They are named after an indicator genus, the arctic and alpine plant Dryas, the remains of which are found in higher concentrations in deposits from colder periods.

Where are Dryas found?

Older Dryas species are usually found in sediment below the bottom layer of the bog. Indicator species are the Alpine plants:

Can you capture the old Dryas?

Capturing the Older Dryas through high resolution dating continues to be of concern to researchers in climatology.

Dating

The dates of this period are approximately 16,050-13,050 BC, from Roberts, 1998. A date from Kilkeel, Northern Ireland, extends the start of the period to as early as 17,050 BC.

Late Pleistocene climate sequence

The complete sequence of late Pleistocene climatic periods defined for northern Europe are the Oldest Dryas, the Bölling (interstadial), the Older Dryas (stadial), the Allerød (interstadial), and the Younger Dryas (stadial). The Holocene begins immediately afterward. The last three just mentioned are also Blytt-Sernander periods.

Flora

During the Oldest Dryas, a treeless Europe similar to the Arctic tundra presented itself. It contained shrubs and herbaceous plants such as:

Fauna

Species are mainly Arctic; however, during the glacial maximum the warmer weather species had withdrawn into refugia. Starting in the oldest Dryas they began to repopulate Europe.

Human prehistory

Human cultures in Europe were upper Palaeolithic and belonged to Cro-Magnon man. Neanderthals had long since disappeared either by replacement or by amalgamation with modern man. The Magdalenian culture of reindeer hunters prevailed in west Europe. From the Carpathians eastward the Epigravettian continued the prior Gravettian.

How long ago was the Younger Dryas?

The change to glacial conditions at the onset of the Younger Dryas in the higher latitudes of the Northern Hemisphere, between 12,900 and 11,500 calendar years BP, has been argued to have been quite abrupt. It is in sharp contrast to the warming of the preceding Older Dryas interstadial. Its end has been inferred to have occurred over a period of a decade or so, but the onset may have even been faster. Thermally fractionated nitrogen and argon isotope data from Greenland ice core GISP2 indicate that its summit was around 15 °C (27 °F) colder during the Younger Dryas than today.

What was the Younger Dryas?

The Younger Dryas was a period of climatic change , but the effects were complex and variable. In the Southern Hemisphere and some areas of the Northern Hemisphere, such as southeastern North America, a slight warming occurred.

How long did the Younger Dryas last?

Depending on the specific ice core analysis consulted, the Younger Dryas is estimated to have lasted 1,150–1,300 years. Measurements of oxygen isotopes from the GISP2 ice core suggest the ending of the Younger Dryas took place over just 40 to 50 years in three discrete steps, each lasting five years.

What is the youngest stadial?

The Younger Dryas is the youngest and longest of three stadials, which resulted from typically abrupt climatic changes that took place over the last 16,000 years. Within the Blytt–Sernander classification of north European climatic phases, the prefix "Younger" refers to the recognition that this original "Dryas" period was preceded by a warmer stage, the Allerød oscillation, which, in turn, was preceded by the Older Dryas, around 14,000 calendar years BP. That is not securely dated, and estimates vary by 400 years, but it is generally accepted to have lasted around 200 years. In northern Scotland, the glaciers were thicker and more extensive than during the Younger Dryas . The Older Dryas, in turn, was preceded by another warmer stage, the Bølling oscillation, that separated it from a third and even older stadial, often known as the Oldest Dryas. The Oldest Dryas occurred about 1,770 calendar years before the Younger Dryas and lasted about 400 calendar years. According to the GISP2 ice core from Greenland, the Oldest Dryas occurred between about 15,070 and 14,670 calendar years BP.

How long did the Dryas period last?

The Younger Dryas was the most recent and longest of several interruptions to the gradual warming of the Earth's climate since the severe LGM, about 27,000 to 24,000 years BP.

Why did the Younger Dryas occur?

The current theory is that the Younger Dryas was caused by significant reduction or shutdown of the North Atlantic "Conveyor", which circulates warm tropical waters northward, in response to a sudden influx of fresh water from Lake Agassiz and deglaciation in North America.

When did the Dryas come back?

The Younger Dryas (around 12,900 to 11,700 years BP) was a return to glacial conditions after the Late Glacial Interstadial, which temporarily reversed the gradual climatic warming after the Last Glacial Maximum (LGM) started receding around 20,000 BP.

Overview

Flora

Fauna

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Further reading

External links

Dates

• In the Greenlandoxygen isotope record, the Older Dryas appears as a downward peak establishing a small, low-intensity gap between the Bølling and the Allerød. This configuration presents a difficulty in estimating its time, as it is more of a point than a segment. But which point, and how long a segment should be assigned? The segment is small enou...

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Description

Flora

Fauna

Humans

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