Archive for Earth Sciences Forum This site is dedicated to the Earth Sciences. We are here for you to discuss issues regarding any aspect of the Earth sciences, at all levels of knowledge. Questions are welcomed, as are open scientific debates. Enjoy!!!
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NileQueen
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Arctic OceanA good link for info on formation of the Arctic Ocean basin is here
http://www.geus.dk/program-areas/...eports/geus_spec_rep_11_04-uk.htm
| Quote: | Scientific drilling in the Arctic Ocean and
the site survey challenge:
Tectonic, paleoceanographic and
climatic evolution of the Polar Basin
JEODI Workshop, Copenhagen, Denmark,
January, 2003
Kristoffersen, Y. and Mikkelsen, N. (Eds.) |
This is International Polar Year btw. 2007-2008
http://www.ipy.org/
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The International Polar Year is a large scientific programme focused on the Arctic and the Antarctic from March 2007 to March 2009.
IPY, organized through the International Council for Science (ICSU) and the World Meteorological Organization (WMO), is actually the fourth polar year, following those in 1882-3, 1932-3, and 1957-8. In order to have full and equal coverage of both the Arctic and the Antarctic, IPY 2007-8 covers two full annual cycles from March 2007 to March 2009 and will involve over 200 projects, with thousands of scientists from over 60 nations examining a wide range of physical, biological and social research topics. It is also an unprecedented opportunity to demonstrate, follow, and get involved with, cutting edge science in real-time.
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I am currently studying the Arctic with a view to understanding of how the Laurentian ice sheet grew (what was the source of moisture?) and how it melted. Heinrich events were a periodic massive release of icebergs from the LIS (and perhaps the European ice sheet) every 5-11,000 years or so.
The binge-purge hypothesis is one of the ideas about why this occurred. The icesheet would load and spread out and then these massive discharges would occur. So what is the source for reloading of the ice
when sea level is as low as it was at the LGM? The Arctic Ocean would have been 200 ft. lower or so at LGM with continental shelves exposed.
I wonder about volcanism and geothermal heat on the sea floor. Late pleistocene volcanism was pretty high compared to the last 100,000 years.
http://www.gisp2.sr.unh.edu/Contri_Series/full/05.html#8
| Quote: | A 110,000-year record of explosive volcanism from the GISP2 (Greenland) ice core
Zielinski, G.A., P.A. Mayewski, L.D. Meeker, S. Whitlow and M. Twickler
Quat. Res., Vol. 45, p. 109-118, 1996
The time series of volcanically-produced sulfate from the GISP2 ice core is used to develop a continuous record of explosive volcanism over the past 110,000 yr. We identified ~850 volcanic signals (700 of these from 110,000 to 9000 years ago) with sulfate concentrations greater than that associated with historical eruptions from either equatorial or mid-latitude regions that are known to have perturbed global or Northern Hemisphere climate, respectively. This number is a minimum because decreasing sampling resolution with depth, source volcano location, variable circulation patterns at the time of the eruption, and post-depositional modification of the signal can result in an incomplete record. The largest and most abundant volcanic signals over the past 110,000 yr, even after accounting for lower sampling resolution in the earlier part of the record, occur between 17,000 and 6000 yr. ago, during and following the last deglaciation. A second period of enhanced volcanism occurs 35,000-22,000 yr. ago, leading up to and during the last glacial maximum. These findings further support a possible climate-forcing component in volcanism. Increased volcanism often occurs during stadial interstadial transitions within the last glaciation, but this is not consistent over the entire cycle. Ages for some of the largest known eruptions 100,000-9000 yr. ago closely correspond to individual sulfate peaks or groups of peaks in our record. |
Here is a recent report on methane seeps in the Arctic. 5 Feb 2007
http://www.mbari.org/news/news_releases/2007/paull-plfs.html
| Quote: | Methane bubbling through seafloor creates undersea hills
According to a recent paper published by MBARI geologists and their colleagues, methane gas bubbling through seafloor sediments has created hundreds of low hills on the floor of the Arctic Ocean. These enigmatic features, which can grow up to 40 meters (130 feet) tall and several hundred meters across, have puzzled scientists ever since they were first discovered in the 1940s. |
Thermal pulsing now in the Arctic?
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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L01603, doi:10.1029/2006GL027977, 2007
Origin of pingo-like features on the Beaufort Sea shelf and their possible relationship to decomposing methane gas hydrates
Charles K. Paull
Monterey Bay Aquarium Research Institute, Moss Landing, California, USA
William Ussler III
Monterey Bay Aquarium Research Institute, Moss Landing, California, USA
Scott R. Dallimore
Natural Resources Canada, Sidney, British Columbia, Canada
Steve M. Blasco
Natural Resources Canada, Dartmouth, Nova Scotia, Canada
Thomas D. Lorenson
U.S. Geological Survey, Menlo Park, California, USA
Humfrey Melling
Fisheries and Oceans Canada, Sidney, British Columbia, Canada
Barbara E. Medioli
Natural Resources Canada, Ottawa, Ontario, Canada
F. Mark Nixon
Natural Resources Canada, Ottawa, Ontario, Canada
Fiona A. McLaughlin
Fisheries and Oceans Canada, Sidney, British Columbia, Canada
Abstract
The Arctic shelf is currently undergoing dramatic thermal changes caused by the continued warming associated with Holocene sea level rise. During this transgression, comparatively warm waters have flooded over cold permafrost areas of the Arctic Shelf. A thermal pulse of more than 10°C is still propagating down into the submerged sediment and may be decomposing gas hydrate as well as permafrost. A search for gas venting on the Arctic seafloor focused on pingo-like-features (PLFs) on the Beaufort Sea Shelf because they may be a direct consequence of gas hydrate decomposition at depth. Vibracores collected from eight PLFs had systematically elevated methane concentrations. ROV observations revealed streams of methane-rich gas bubbles coming from the crests of PLFs. We offer a scenario of how PLFs may be growing offshore as a result of gas pressure associated with gas hydrate decomposition.
Received 23 August 2006; accepted 20 November 2006; published 5 January 2007.
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Another interesting article was a recent survey of undersea volcanoes, but some of these could be non-volcanic as they were surveying for structures I think.
http://environment.newscientist.c...s-revealed-beneath-the-waves.html
excerpt
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But there is a multitude of small volcanoes that have gone undetected. The only way of identifying them is to manually find their outline on sonar measurements taken from ships.
Since the late 1960s, research vessels have been criss-crossing the oceans using sonar instruments to measure the depth of the ocean floor. They have generated 40 million kilometres of linear profiles showing the topography of the ocean bed between 60° North – the latitude of southern Alaska – and 60° South – corresponding to the tip of Patagonia.
But until now, no one had been able to sift through them all. So, Hillier and a colleague designed a computer programme that was able to analyse the huge amount of data and identify volcano-like shapes in the sonar lines.
The programme found 201,055 volcanoes over 100m tall. Previously, satellite data had identified 14,164 volcanoes over 1500 m high.
Hillier then extrapolated the data to estimate how many volcanoes exist beyond the areas the research vessels sounded out. He estimates there are about 39,000 volcanoes that are higher than 1000 m, leaving nearly 25,000 yet to be directly discovered.
Surprising distribution
Hiller says he was surprised to find that the density of small volcanoes dropped in the area around Iceland, as Iceland is known to be a hotspot for volcanic activity.
Another surprise was that he found fewer volcanoes on the seabed around Hawaii, another volcanic hotspot. He says his findings may mean that researchers need to re-assess their understanding of how submarine volcanoes are formed.
In 2006, a team of researchers from Japan discovered a new type of volcano which also defied conventional theories of volcanism. The "petit-spot" volcanoes, aged between one to eight million years old, did not sit at tectonic plate boundaries or over volcanic hotspots (see New type of volcano fires imaginations).
Journal reference: Geophysical Research Letters (DOI: 10.1029/2007GL029874)
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billiards
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Good luck with that, personally I would like to know how the deep water is formed up there, seems to be a gap in the knowledge there.
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Andre
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Not completely on or of thread but I was captured by fig 1.2 of the link:
| Quote: | | Figure 1.2 Outline of the tectonic evolution of the Arctic Ocean (after Green et al.,1986) |
I miss reference to the Turgay strait, straight through the middle of Siberia to the Thethys sea, but anyway, I'd like to discuss another little PETM pet-idea (Paleocene Eocene Thermal Maximum), another major mystery, of which the solution seems to be staring us in the face here.
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NileQueen
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Okay, Andre, if you discuss PETM here, you will need to relate it back to late Pleistocene, LGM and the most recent ice sheets on North america and Eurasia.
NQ 
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