Gulf Stream born 3 million years ago?
Sunday, 20. July 2008, 16:57:13
The formation of the Isthmus of Panama may be one of the most important geologic events in the last 60 million years. Even though only a small sliver of land relative to the sizes of continents, the Isthmus of Panama had an enormous impact on Earth's climate and its environment. By shutting down the flow of water between the two oceans, the land bridge re-routed ocean currents in both the Atlantic and Pacific Oceans. Atlantic currents were forced northward, and eventually settled into a new current pattern, namely the Gulf Stream. With warm Caribbean waters flowing toward the northeast Atlantic, the climate of northwestern Europe grew warmer. (Winters there would be as much as 10°C colder in winter without the transport of heat from the Gulf Stream.) The Atlantic, no longer mingling with the Pacific, grew saltier. Each of these changes helped establish the global ocean circulation pattern in place today.
Before the present-day isthmus was created a significant body of water (referred to as the Central American Seaway*)) separated the continents of North and South America. Beneath the surface, two plates of the Earth's crust were slowly colliding, forcing the Pacific Plate to slide under the Caribbean Plate. The pressure and heat caused by this collision led to the formation of underwater volcanoes, some of which grew large enough to form islands as early as 15 million years ago. Eventually the volcanic activity formed a thin strip of land linking the Americas and separating the Pacific and Atlantic oceans. So far it was believed that the isthmus finally had formed between North and South America about 3 million years ago - but is that so?
Engineers digging to widen the Panama Canal have uncovered more than 500 fossils from animals that lived before the land bridge linked North and South America. By comparing the Panama discoveries to fossil records from each continent, palaeontologists hope to determine where the individual animals came from. Volcanic debris embedded in the same layer of rock as the fossils will help pinpoint the time when the animal was found on either side of the land bridge. Determining exactly when this closure happened could be key to understanding the link between major changes in ocean currents and our climate, providing insight into the impact of global warming. Was the closure linked to the start of the ice age is one of the questions.
• http://www.msnbc.msn.com/id/25726314/
*)
The Central American Seaway, also called the Panamanic Seaway or Inter-American Seaway formed in the Mesozoic (200-154 million years ago) during the separation of the Pangaean supercontinent.
See also my post on Ocean (and atmospheric) circulation.
PS: In 2004 Oceanus posted a great article on line titled How the Isthmus of Panama Put Ice in the Arctic with more in depth information.
PS of 11 August 2008:
See also my continuation at http://my.opera.com/nielsol/blog/2008/08/11/panama
Before the present-day isthmus was created a significant body of water (referred to as the Central American Seaway*)) separated the continents of North and South America. Beneath the surface, two plates of the Earth's crust were slowly colliding, forcing the Pacific Plate to slide under the Caribbean Plate. The pressure and heat caused by this collision led to the formation of underwater volcanoes, some of which grew large enough to form islands as early as 15 million years ago. Eventually the volcanic activity formed a thin strip of land linking the Americas and separating the Pacific and Atlantic oceans. So far it was believed that the isthmus finally had formed between North and South America about 3 million years ago - but is that so?Engineers digging to widen the Panama Canal have uncovered more than 500 fossils from animals that lived before the land bridge linked North and South America. By comparing the Panama discoveries to fossil records from each continent, palaeontologists hope to determine where the individual animals came from. Volcanic debris embedded in the same layer of rock as the fossils will help pinpoint the time when the animal was found on either side of the land bridge. Determining exactly when this closure happened could be key to understanding the link between major changes in ocean currents and our climate, providing insight into the impact of global warming. Was the closure linked to the start of the ice age is one of the questions.
• http://www.msnbc.msn.com/id/25726314/
*)
The Central American Seaway, also called the Panamanic Seaway or Inter-American Seaway formed in the Mesozoic (200-154 million years ago) during the separation of the Pangaean supercontinent.
See also my post on Ocean (and atmospheric) circulation.
PS: In 2004 Oceanus posted a great article on line titled How the Isthmus of Panama Put Ice in the Arctic with more in depth information.
PS of 11 August 2008:
See also my continuation at http://my.opera.com/nielsol/blog/2008/08/11/panama
WIDGETIZE
piombaldo # 30. July 2008, 13:10
nielsol # 30. July 2008, 13:40
Driscoll et al.
Science 282, 436 (1998);
DOI: 10.1126/science.282.5388.436
http://www.sciencemag.org/cgi/content/abstract/282/5388/436
might give you some of the answers together with other (older) references.
It states a.o. that major ice sheet growth in Eurasia, Greenland, and North America is recorded by a d18O enrichment in benthic foraminifera between 3.1 and 2.5 million years ago (Ma)
and by the massive appearance of ice-rafted debris in northern high-latitude oceans since 2.7 Ma
Unnecessary to say that exact dating is a problem.