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Pioneering drilling in Arctic pack ice International drilling project near the North Pole discovers evidence of warm temperatures and fresh water millions of years ago Alan Bailey Petroleum News Staff Writer
The artificial palm tree that someone once placed on the shore of Endicott Island, off Alaska’s North Slope, might not be quite as out of place as it might appear. It seems that about 55 million years ago surface temperatures in the Arctic Ocean reached about 68 degrees Fahrenheit. Not only that — about 48 million years ago the ocean basin contained fresh water.
Those were two of the findings from a well drilled near the North Pole by the 2004 Arctic coring expedition, an international initiative that formed part of what’s known as the Integrated Ocean Drilling Program, Kate Moran, associate professor of ocean engineering and oceanography at the University of Rhode Island, told an Anchorage audience Oct. 14. The current ocean drilling program has evolved from the Deep Sea Drilling Project of the early 1980s and the later Ocean Drilling Program, Moran said. All of these programs have set out to enhance our understanding of the Earth through drilling into the crust beneath the deep oceans. Determining climate changes The main objectives of the 2004 Arctic coring expedition were to determine polar climate changes over the past 50 million to 56 million years and to obtain information about sea ice history, Moran said. Prior to the expedition Arctic Ocean data was only available for about the past 1.5 million years, she said. The expedition would require a drilling platform specifically designed for use in the Arctic ice.
“The Arctic coring expedition (involved) the first mission-specific (drilling) platform (under the Integrated Ocean Drilling Program) and it was operated by a European group that was led by the British Geological Survey,” Moran said.
The idea for the expedition went back to 1991, when non-nuclear icebreakers crossed the North Pole for the first time.
“We collected by luck a beautiful, multi-channel seismic record across the (Lomonosov) Ridge,” Moran said.
The Lomonosov Ridge extends across the center of the Arctic Ocean and consists of a supposed sliver of continental crust. The seismic section displayed a sequence of sedimentary strata on the ridge — these strata ought to contain vital evidence about the climatic history of the region. Daunting challenges Moran described how the 2004 expedition addressed the daunting challenges of drilling far inside the Arctic pack ice, close to the North Pole. To navigate through the pack ice and then drill in a moving ice sheet the team assembled a fleet consisting of the drilling ship, a large diesel-powered icebreaker and a massive Russian nuclear-powered icebreaker.
The drilling ship consisted of a small icebreaker especially fitted with a drilling derrick and helicopter deck.
“Icebreakers are the (drilling) platform of choice in the Arctic Ocean,” Moran said.
The team identified several potential drilling sites, to ensure that there would be at least one site where drilling would be possible in the ice.
“If we went to one location and it was just packed with ice we would maybe have to go to a different location,” Moran said. Drilling in the ice One of the biggest challenges that the team faced was an inability to use standard deepwater dynamic positioning techniques in sea ice-covered ocean.
And the drilling required stationing the drilling ship on site for nine days in very heavy ice conditions. The Russian icebreaker circled the well location to disrupt the ice and prevent the moving ice sheet from shifting the drillship. At the same time the diesel icebreaker protected the drillship from the ice. An ice management team used radar reflectors positioned on the ice to measure ice velocities relative to the ships. Cell phone coverage on all of the ships enabled easy ship-to-ship communications.
The project involved open-hole drilling to about 400 meters below the sea floor.
“What we mainly do is send coring tools down through the center of the drill string and 100 percent core recovery is our goal,” Moran said. “We reach that (goal) most of the time.”
A team of paleontologists used microfossils to date the rocks in the cores.
The drilling confirmed that the Lomonosov Ridge does consist of continental crust, rather than oceanic crust. And a determination of ancient temperatures, using oxygen isotopes and other evidence from the drill cores, showed a transition at depths between 220 to 200 meters from an ancient greenhouse world of relatively high temperatures to the more icehouse Arctic world of today. Finding the thermal maximum Towards the bottom of the well the team found what is called the Paleo-Eocene thermal maximum, or PETM, a known high point in temperature trends about 55 million years ago. That’s the point at which the surface of Arctic Ocean appears to have attained temperatures of about 68 F, showing that the whole of the Earth including the North Pole became warm at that time.
“Which is quite a bit different than what was (previously) modeled … that there was a very large temperature gradient between the equator and the poles at that time period,” Moran said.
Equally intriguing were at least two 48 million year old horizons that contained masses of well-preserved azolla plants — the oil industry uses azolla marker horizons in some Arctic drilling, Moran said. Azolla is a floating plant that lives in freshwater and the existence of azolla horizons leads to the surprising conclusion that the once-isolated Arctic Ocean basin contained relatively warm freshwater millions of years ago. Early freeze up Other evidence points to colder conditions in the Arctic starting about 42 million years ago, an earlier freeze-up than had previously been supposed. And the research team is in the process of reconstructing the sea ice history of the Arctic Ocean by tracing the changing characteristics of the sediments over time.
“The surprise is that ice we think was present much earlier than was thought,” Moran said.
Measurements of magnetism in the well cores showed the characteristic fluctuations and reversals of the Earth’s magnetic field that have been recorded in rocks of similar age elsewhere.
“We have really good paleomagnetics,” Moran said.
The discovery of the magnetic fluctuations in all but the upper few meters of the Arctic Ocean well dispels a widely held belief that the fluctuations are not clearly recorded in rocks formed under Arctic conditions.
Moran said that a publication of the expedition’s initial findings should come out in January. Drill core samples will become available to the public at some time in 2006. Meantime scientists are preparing proposals for future drilling in the Chukchi or Beaufort Seas and Moran invited new ideas for drilling objectives.
“We can’t go drill for oil in the program,” Moran pointed out. “But certainly stratigraphic sections must be of great interest,” she said.
And how do the results from the expedition help our understanding of what is happening in the modern-day Arctic?
Many scientists believe that the rapid rise in temperatures in the PETM is directly analogous to modern global warming trends. So, understanding the response of the planet to that PETM warming may shed light on the potential impact of global warming, Moran said. And scientists are particularly interested in how increased freshwater inputs to the Arctic Ocean might impact global ocean currents and temperature patterns throughout the world.
It’s all food for thought — maybe one day there will be a real palm tree at Endicott.
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