Did a comet cause the the Younger Dryas cooling?

Introduction

The Younger Dryas was a global cataclysm of unprecedented proportions, was a comet impact responsible? The Younger Dryas was but one of a series of climate oscillations since the last Glacial maximum, 27,000 years ago. However, the temperature drop was sudden, occurring in decades. Most importantly, two other factors were present.

Firstly, there was a megafaunal extinction event in North America. Secondly, a black mat layer exists in the archaeology record that is concurrent with the onset of cooling. Consequently, the black matt indicates an impact event. More recent research has narrowed the time frame to within fifty years for both events. The researchers claim that the data is accurate to within 30 years. However, they also claim that the impact occurred 50 years after the cooling began. The author would suggest that the impact is too close to the margin of error to call.

Causes of the Younger Dryas

Atlantic meridional overturning circulation (AMOC

The Atlantic meridional overturning circulation (AMOC) is a subsurface ocean current that transports heat from the Southern hemisphere to the North. As a result, it is thought to make the Northern hemisphere warmer than it would otherwise be. One of the main theories for the Younger Dryas cooling is a disruption to this current.

It is thought that a massive influx of fresh water into the North Atlantic, from a breached ice dam, stopped the thermohaline circulation. Consequently a sudden cooling struck the Northern hemisphere. The largest ice dammed lake at the time was lake Missoula.

Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. The lake measured about 7,770 square kilometres (3,000 sq mi) and contained about 2,100 cubic kilometres (500 cu mi) of water, half the volume of Lake Michigan.[1]

The comet Impact hypothesis

The comet impact hypothesis was first proposed in 2008 by Firestone, West Et Al. This proposed multiple air bursts from a fragmenting comet. The impacts led to rapid cooling and mass extinctions. Most importantly, there is a black matt layer dated to the Younger Dryas boundary, YDB.

The black matt contains impact proxies such as high-temperature spherules and melt glass. The proponents suggest that a massive amount of biomass burring occurred leading to megafaunal extinctions. Consequently, a “nuclear winter” occurred due to all the particulate matter in the atmosphere.

Conclusion

There is strong evidence for a comet impact although there is still a long standing bias against catastrophism, by mainstream academics.


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