What Effect Coming Ice Age on North of 30th Parallel Boating?

ImaginaryNumber · Oct 7, 2012

hoytedow said: ↑

I found this article about the J&J Hunt site located off the NW coast of Florida interesting. http://en.wikipedia.org/wiki/J&J_Hunt_Submerged_Archaeological_Site
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Hoytedow, thank you for pointing out so clearly what happens when sea levels rise. In another few hundred years archeologists may be doing underwater surveys of Miami or London.

From the above link:

Sea-level rise

During the Late Glacial Maximum (ca. 18,000 years ago) the continental shelf around the Gulf Coast of Florida was exposed for a least 185 km from the present-day mouth of the Aucilla River. At this time and for the next 7,000 years the sea-level was around 90 m lower than today’s present level. Then around 14,000 B.P. until approximately 11,000 B.P., at the onset of the Younger Dryas, massive melting of the ice sheets resulted in sea-level rise and transgression of the continental shelf to about 140 km from the mouth of the Aucilla River (Faught 2004b). A second glacial melting began after 10,000 B.P. and lasted until about 7,000 B.P. when sea levels became relatively constant. It is important to note that as sea levels rose it forced people settled along the coast to move further and further inland. During late Pleistocene and early Holocene times, the coastline was much farther out on the continental shelf, and this segment of the PaleoAucilla was forested and well inland. Later, during the middle Holocene stages of transgression, the segment was more of a wide grassy marsh with brackish water tidal creeks and oysters. In this continental shelf setting, submerged archaeological sites remain in clustered arrays accessible by underwater archaeological methods, and the data provide a critical supplement to our present understanding of late Pleistocene and early Holocene settlement patterns and paleolandscape utilization(2004b). The Underwater Archaeology of Paleolandscapes, Apalachee Bay, Florida. American Antiquity, Vol. 69, No. 2. (Apr., 2004), pp. 275-289.
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Wikipedia: Long-Term Sea Level Changes

Various factors affect the volume or mass of the ocean, leading to long-term changes in eustatic sea level. The primary influence is that of temperature on seawater density and the amounts of water in rivers, lakes, glaciers, polar ice caps and sea ice. Over much longer geological timescales, changes in the shape of the oceanic basins and in land/sea distribution will also affect sea level.

Observational and modelling studies of mass loss from glaciers and ice caps indicate a contribution to sea-level rise of 0.2 to 0.4 mm/yr averaged over the 20th century. Over this last million years, whereas it was higher most of the time before then, sea level was lower than today. It was around 150 meters below the present level as long as a couple tens thousands years 180 thousands years ago.

Sea level reached 120 meters below current sea level at the Last Glacial Maximum 19,000-20,000 years ago.
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hoytedow · Oct 7, 2012

Another interesting site: http://www.grahamhancock.com/forum/BadrinaryanB1.php

The next ice age will necessitate re-tooling harborage and all the supporting framework if we want to continue reaping the sea's bounty.

ImaginaryNumber · Oct 8, 2012

Coral atolls grow as sea levels rise (Basic level explanation)

Thousands of coral atolls have "drowned" in the past when they were unable to grow fast enough to maintain a presence at sea level

Coral atolls don't always keep grow[sic] well enough to keep in touch with sea level. The ocean is littered with thousands of former coral reefs and atolls which "drowned" when they failed to grow fast enough to match sea level. Being generally less than 3 metres above sea level they are particularly vulnerable to sea level rise.

Recent work shows that people living on coral atolls in the Pacific will suffer once sea level rises above the solid reef foundations which formed during a period of locally higher sea level 4000 to 2000 years ago. Waves will begin to pound and erode the atolls long before they are submerged.

Coral atoll formation

Coral reefs grow only in warm waters of the world and form as generations of coral build upon the "bones of their ancestors". Given the right conditions coral are able grow fast enough to keep pace with moderate rates of sea level rise.

It was Charles Darwin whom first realized that coral atolls are the remains of submerged ocean volcanoes (Darwin 1842) with successive generations of coral growing on top of a slowly sinking volcano. This was later confirmed by deep drilling on coral atolls (Royal Society of London 1904, Ladd & Ingerson 1953)

We now know that sea level has fluctuated a lot during the Quaternary ice ages of the last few million years, so the process is more complex than Darwin suggested. Reef building on the atoll top has stopped when sea level fell and began growing again many thousands of years later when each ice age ended and sea level flooded the atoll top. The top 10 -15 metres of many atolls represent the "recent" growth during the current interglacial, the Holocene.

Figure 1. Atoll history through ice age sea level fluctuation. a) sea level thousands of years before & up to present. b) Atoll form relative to sea level. From Woodroffe 2007

A long history of reef drowning

Just like Goldilocks, coral reefs are very picky. Growth can slow down when waters become too hot, too cool or too acidified (Flood 2001), (Scheibner & Speijer 2008).Guyots are drowned ancient coral atolls, and thousands of these lie beneath the Pacific sea surface.

Coral reef growth during the Holocene, like that of ancient reefs show evidence of having " temporarily drowned" at some point. Many regions also harbour relict reefs which have permanently drowned during the Holocene. One vast relict complex exists in deeper water off the Great Barrier Reef for example.

Higher Pacific sea level in the Holocene

At around 8-9 thousands years ago sea level caught up with the tops of the eroded atolls and new Holocene reef growth began to be cemented over the older reef foundations. Sea level reached a highstand in the Pacific between 4-2000 years ago (Dickinson 2003, Woodroffe & McLean 1998). Coral reef tops grew to this higher sea level but were exposed once local sea level fell again (Mitrovica & Milne 2002).

The end of atoll nations

Now that global sea level is rising once more the solid foundations (reef flats) which support the stable Pacific atolls, will be overtopped by the sea at some point. Many of these are 0.5 to 1 metre above local high tide. Submerging these solid foundations will lead to the atolls being vulnerable to wave damage. Erosion will begin to sweep away the rubble, sediment and thin soils, making them uninhabitable at some point in the future. Dickinson 2009 estimates that by mid to late 21st century most atolls will be awash.

Homeless

Although they appear like permanent features, Pacific coral atolls have only existed for about two thousand years, and are stable because the solid foundations protect them from major erosion. This protection is only likely to continue until mid century for some atolls. So, although coral atolls may indeed grow as sea level rises, this hasn't always been the case in the past, and won't be the case in the future.
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hoytedow · Nov 7, 2012

We are all going to freeze.

ImaginaryNumber · Nov 7, 2012

hoytedow · Nov 7, 2012

hoytedow said: ↑

Somebody out there has lost their sense of humor.
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Seems it was me.

hoytedow · Jul 14, 2013

Global cooling as the result of one or more powerful volcanic eruptions will likely cause depressed shipping of grain due to its impact on grain harvests. Our history as a grain exporter will be affected in a very negative way, endangering both the recipients of needed grain and the maritime sector providing sustenance across the globe.

The damage to the economy will severely hamper any ability to enjoy recreational boating as it is practiced now.
http://www.geology.sdsu.edu/how_volcanoes_work/climate_effects.html

"...1815, the eruption of Mt. Tambora, Indonesia, resulted in an extremely cold spring and summer in 1816, which became known as the year without a summer. The Tambora eruption is believed to be the largest of the last ten thousand years. New England and Europe were hit exceptionally hard. Snowfalls and frost occurred in June, July and August and all but the hardiest grains were destroyed."

hoytedow · Jul 15, 2013

Moderator Jeff, please close this thread.

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What Effect Coming Ice Age on North of 30th Parallel Boating?

ImaginaryNumber Imaginary Member

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