Althought this longish NYT article focuses on arctic sediments and possible oil resources, it's also an update on the latest thinking about climate change. A lot of people would like to know what caused that vast methane release.
... The cores provide the first evidence that vast amounts of organic material created by plankton and other life settled on the seabed, experts say. That kind of carbon-rich accumulation is a vital precursor to the formation of oil.
Some of the deepest, oldest, most carbon-rich layers, dated to around 55 million years ago, formed during a period called the Paleocene-Eocene Thermal Maximum, when the world was running a raging temperature. Scientists believe that this relatively brief period, far warmer than the present, was caused by a spike in heat-trapping greenhouse gases far greater than the human-caused buildup that has occurred over the last century.
The initiating cause was a vast release of submarine deposits of frozen methane, a powerful greenhouse gas, but scientists do not yet know whether those gases were liberated by volcanic activity, a shift in warm sea currents, or some other force.
Around 49 million years back, with the climate cooling and the atmosphere's greenhouse burden declining, the retrieved shafts of sediment also speak of an extraordinary, short-lived era of several hundred thousand years when so much warm fresh water apparently topped the Arctic's oxygen-starved salty depths that the polar sea became matted with tiny Azolla ferns, resembling the duckweed that can choke suburban ponds.
Altogether, about 600 vertical feet of sediment from the ridge is rich dark organic material, implying that there could easily be two vertical miles or more of similar organic layers in the deeper adjacent basins, said Dr. Henk Brinkhuis, a geobiologist from Utrecht University in the Netherlands who participated in the coring project....
... The preliminary analysis reveals that the Arctic Ocean has been constantly icy for at least 15 million years, far longer than scientists had previously theorized. Dr. Moran said scientists had previously put the last ice-free conditions at four million to seven million years ago.
Experts involved in the research said these findings added sobering context to the current Arctic warming trend, which climatologists have linked to accumulating greenhouse-gas emissions and say could lead to a largely ice-free sea in summers this century.
No one expects ferns to cover the polar sea any time soon, but some experts involved with the research said the recent changes in the Arctic could result in a long-lasting warming that is likely to change the nature of the Arctic profoundly, for better and worse. In outlining the pattern of change during and after the last big Arctic warm-up, 55 million years ago, the new cores show "you can get a really strong cascade" toward warming that then can take hundreds of thousands of years to reverse, said Dr. Brinkhuis.
Whatever the future holds, it is becoming clearer with every new scientific poke at the freshly recovered shafts of layered shale, microscopic plankton fossils, pebbles and other material that the coring project will provide an unparalleled view of past climate changes at the top of the world, Arctic experts said...
... The $12.5 million project, financed by Europe, was conducted under the auspices of the Integrated Ocean Drilling Program, which is systematically coring seabeds around the world to reveal geological history.
... One of the most remarkable revelations is that the Arctic Ocean apparently briefly bloomed into a great matted soupy superlake.
Dr. Brinkhuis, who had worked for oil companies, said that previous drilling efforts by oil teams around the perimeter of the Arctic also captured this brief flowering of water plants, but no one had conceived that the layer might hint that the entire Arctic basin was one great matted pond.
"It's spectacular," he said. "Right at this transition from supergreenhouse to cooling, that's where there's this evidence of a bathtub situation there that is so fresh that this Azolla can really bloom and boom."
He said it was possible that the fast-growing plants, by absorbing huge amounts of carbon dioxide, might have contributed to the eventual decline in the atmosphere's greenhouse gas concentration and climate cooling...
Note this was a European expedition. Perhaps in the US research into climate change is a dangerous subject.