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Tue, 20 Oct 2020
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Ice Ages and Sea Level

The Earth is currently in an interglacial period of an ice age that started about two and a half million years ago. The Earth's current ice age is primarily caused by Antarctica drifting over the South Pole 30 million years ago. This meant that a large area of the Earth's surface changed from being very low-albedo ocean to highly reflective ice and snow. The first small glaciers were formed in Antarctica perhaps as long ago as 40 million years. They expanded gradually until, about 20 million years ago, a permanent ice sheet covered the whole Antarctic continent. About 10 million years later, glaciers appeared on the high mountains of Alaska, and about 3 million years ago, ice sheets developed on lower ground in high northerly latitudes.

Telescope

Ice Age Ends Smashingly: Did a comet blow up over eastern Canada?

Evidence unearthed at more than two dozen sites across North America suggests that an extraterrestrial object exploded in Earth's atmosphere above Canada about 12,900 years ago, just as the climate was warming at the end of the last ice age. The explosion sparked immense wildfires, devastated North America's ecosystems and prehistoric cultures, and triggered a millennium-long cold spell, scientists say.

Ark

Vast Cache of Ice Age fossils found in Los Angeles

Image
© Natural History Museum of Los Angeles County
Exposed left acetabulum of Zed's pelvis. The fossil is from the first complete individual mammoth to have been found in Rancho La Brea.

The Page Museum at the La Brea Tar Pits, part of the Natural History Museum of Los Angeles County family of museums, has announced an endeavor of discovery and research so enormous that it could potentially rewrite the scientific account of the world-famous La Brea Tar Pits and their surrounding area - one of the richest sources of life in the last Ice Age, approximately 40,000 to 10,000 years ago.

Project 23: New Discoveries at Rancho La Brea, undertaken in the heart of urban Los Angeles, has to date uncovered over 700 measured specimens including a large pre-historic American Lion skull, lion bones, dire wolves, saber-toothed cats, juvenile horse and bison, teratorn, coyotes, lynx, and ground sloths. Most rare of all is a well-preserved male Columbian mammoth fossil, about 80% complete, with 10-feet long intact tusks found in an ancient river bed near the other discoveries. This latter fossil is the first complete individual mammoth to have been found in Rancho La Brea. In recognition of the importance of the find, paleontologists at the Page Museum have nicknamed the mammoth "Zed."

"The name signifies the beginning of a new era of research and discovery," according to Dr. John Harris, Chief Curator, Page Museum at the La Brea Tar Pits. "Zed is a symbol of the potential of Project 23 to revolutionize our knowledge about this area."

Bizarro Earth

Climate 'Flickering' Ended Last Ice Age in North Atlantic Region

Lake Kråkenes
© UIB/BCCR
Sediment cores were obtained from Lake Kråkenes in western Norway and from the Nordic seas in order to document the last part of the ice age.
An article published in the journal Nature Geoscience shows that the period towards the end of the ice age was engraved by extreme and short-lived variations, which finally terminated the ice age.

A group of scientists at the Bjerknes Centre for Climate Research and the University of Bergen in Norway, together with colleagues at ETH, Zürich, combined terrestrial and marine proxy palaeo-data covering the latest part of the ice age to improve our understanding of the mechanisms leading to rapid climatic changes.

The Younger Dryas event, which began approximately 12,900 years ago, was a period of rapid cooling in the Northern Hemisphere, driven by large-scale reorganizations of patterns of atmospheric and oceanic circulation. Environmental changes during this period have been documented by both proxy-based reconstructions from sediment archives and model simulations, but there is currently no consensus on the exact mechanisms of onset, stabilization, or termination of the Younger Dryas. In contrast to existing knowledge, the Nature article shows that the climate shifted repeatedly from cold and dry to wet and less cold, from decade to decade, before interglacial conditions were finally reached and the climate system became more stable.

Satellite

How to Search for Ice Age Aliens

Ice Age
© Unknown
Could an alien astronomer have detected life on Earth during an ice age? Recent work has calculated how past climate extremes affected the light reflected from vegetation out into space. The results could give hope to our own search for life on distant worlds.

From far away, our planet is a single faint speck of light in the sky. Although we have sent radio messages out to potential extraterrestrial listeners, none of these signals have traveled more than a few tens of light years.

However, Earthlings have been broadcasting their presence to the galaxy for millions of years. Terrestrial plants reflect strongly in the infrared, resulting in a distinctive feature (called the vegetation red edge or VRE) in the light bouncing off the Earth's surface.

Igloo

Kelp genetics reveals Ice Age climate clues

Ice berg

Sea ice extended further north in the Southern Ocean during the last Ice Age than previously thought, a New Zealand research team has found in a study that could improve predictions of climate change.

The team from the University of Otago, led by PhD student Ceridwen Fraser, delved deep into the genetic code of modern-day bull kelp from samples taken from many sub-Antarctic islands, as well as New Zealand and Chile.

The findings showed that southern bull kelp, Durvillaea antarctica, had only recolonised the sub-Antarctic islands in the past 20,000 years after the retreat of sea ice.

Clock

Slippery Slope: Ice Age Cometh in Five Years

It's time for some straight talk. No more beating around the bush. I no longer want to evade an issue around whose edges I've been skirting for 12 years. So I'll come right and say it loud and clear: In all probability, we've come to the end of the line.
Unless I'm grievously mistaken, we are about to go extinct. Soon. In 1997 I warned that we are approaching the onset of a new ice age. I wrote that the record shows that ice ages are preceded by a period of about 20 years, and things get very unpleasant as the end of that period approaches.

Contrary to poor Al Gore's alarmist prediction that the planet is approaching the boiling point, it's getting colder - a lot colder. And it's going to get even colder. Spring and fall will disappear, summers will be short and winters longer and increasingly more frigid.

Telescope

Mature Arctic Ivory Gull spotted In Massachusetts for first time in over a century

The temperatures were in the single digits, but not low enough to keep the gawkers away. A celebrity was in town, behind the East Bay Grille, a visitor not seen in these parts in decades, if not longer.

But these weren't paparazzi, and this wasn't a Hollywood star. Rather, they were avid birdwatchers - about 20 in all - braving the frigid air as they scanned the bay and the edges of the breakwater with binoculars and spotting scopes.
Ivory Gull
© Greg Derr/The Patriot Ledger
An ivory gull, a native of the Arctic, has been attracting bird watchers from across New England to Plymouth Harbor.

Star

What's Happening to the Sun? Could its unusual behavior herald a new ice age?

For about 50 years from roughly 1650 to 1700, the Sun took a break from its typical sunspot activity. That phase of solar rest coincided with what we now refer to as "The Little Ice Age" -- a period of cooling on the Earth that resulted in bitterly cold winters, particularly in Europe and North America. Scientists attribute the Little Ice Age to two main causes: increased volcanic activity and reduced solar activity.

Could it happen again? And are we headed there now?
The Sun
© NOAA
The First Cycle 24 Sunspot

Comment: According to the late Rhodes Fairbridge, the alignment of the Jupiter and Saturn, along with the minor planets, control the climate on Earth.
The sun's own orbit, he found, has eight characteristic patterns, all determined by Jupiter's position relative to Saturn, with the other planets playing much lesser roles. Some of these eight have orderly orbits, smooth and near-circular. During such orbits, solar activity is high and Earth heats up. Some of the eight orbits are chaotic, taking a loop-the-loop path. These orbits correspond to quiet times for the sun, and cool periods on Earth. Every 179 years or so, the sun embarks on a new cycle of orbits. One of the cooler periods in recent centuries was the Little Ice Age of the 17th century, when the Thames River in London froze over each winter. The next cool period, if the pattern holds, began in 1996, with the effects to be felt starting in 2010. Some predict three decades of severe cold.
And according Richard Mackey, writing in the Journal of Coastal Research (Special Issue 50, 2007):
In 2007 Ulysses will send information about the solar poles. This could be decisive regarding the predictions about emergent Sunspot Cycle No 24, including the sim hypothesis. According to the sim [Solar Inertial Motion] hypothesis, this cycle should be like Sunspot Cycle No 14, and be followed by two that will create a brief ice age. During the 1920s and '30s Australia's Bureau of Meteorology published research about the sun/climate relationship, especially Sunspot Cycle No 14, showing that it probably caused the worst drought then on record.
...

Rhodes Fairbridge repeatedly emphasised that the entire field of planetary-lunar-solar dynamics, including gravitational dynamics, has to be studied so the dynamics of terrestrial climate can be understood. An improved understanding of the interaction effects of the sunspot cycles and the lunisolar tidal cycles on the earth's climate is necessary, as Rhodes emphasised. When the influence of solar variability is examined in its entirety (as Rhodes insisted it should be), it is clear that the influence of solar variability on the Earth's climate is strongly non-linear, stochastic and significant.
...

The solar inertial motion hypothesis predicts that the period from about 2010 to 2040 will be one of relatively severe cold throughout the world. The hypothesis predicts that the emergent Sunspot Cycle No 24 will be quieter than Sunspot Cycle No 23 and just like Sunspot Cycle No 14, the weakest cycle in the last 100 years, which began in February, 1902 and ended in August,1913.
Not only has Ulysses found that the sun has reduced its output of solar wind to the lowest levels since accurate readings became available, but it's magnetic field has dropped by 20%. At the same time, the solar system appears to be passing through a galactic dust storm.
One possibility is an increased number of sporadic meteors, those not associated with known showers like the summer Perseids or the November Leonids. Meteors are created when something vaporizes in Earth's atmosphere. Space rocks as big as peas and baseballs crash through now and then, but most shooting stars are made of mere dust.

It's also possible, Landgraf said, that the eerie Zodiacal Light -- a "false dawn" caused by sunlight reflecting off space dust -- will be enhanced.

And in general, more material might rain down to Earth from space every year.
Indeed.

And we also know that during the previous ice age the depositional flux of cosmic dust was much higher than during the Holocene.

Gabrielli's paper shows that it was not the sun alone that caused the last ice age:

Depositional Fluxes
©Nature

It bears repeating astronomer Victor Clube's comment:
You first take the modern sky accessible to science, especially during the Space Age, and you look at its' darker debris with a view to relating its behavior to the more accessible human history which we can, in principle, really understand. And by this approach you discover from the dynamics of the material in space which I'm talking about that a huge comet must have settled in a Taurid orbit some 20,000 years ago, whose dense meteor stream for 10,000 years almost certainly produced the last Ice Age.



Better Earth

New Ice Age Maps Point to Climate Change Patterns

Ice Age Map
© Dr Timothy Barrows/Elsevier
New Ice Age maps point to climate change patterns.
New climate maps of the Earth's surface during the height of the last Ice Age support predictions that northern Australia will become wetter and southern Australia drier due to climate change.

An international consortium of scientists from 11 countries has produced the maps, which appear in this week's issue of Nature Geoscience.

Dr Timothy Barrows of the Research School of Earth Sciences at The Australian National University was responsible for the Australian sector of the reconstruction.

"During the last Ice Age - around 20,000 years ago - sea surface temperature was as much as 10 degrees colder than present and icebergs would have been regular visitors to the southern coastline of Australia," Dr Barrows said.

The temperature was estimated by measuring changes in abundance of tiny plankton fossils preserved on the sea floor, together with chemical analyses of the sediment itself.