Oceanography

The ice sheet on West Antarctica just got a little older - 20 million years or so.

The findings indicate that ice sheets first grew on the West Antarctic subcontinent at the start of a global transition from warm greenhouse conditions to a cool icehouse climate 34 million years ago. Previous computer simulations were unable to produce the amount of ice that geological records suggest existed at that time because neighboring East Antarctica alone could not support it.


By analyzing a 150-year-old moss bank on the Antarctic Peninsula, researchers describe an unprecedented rate of ecological change since the 1960s, driven by warming temperatures. 

The researchers looked to the Antarctic Peninsula because it is one of the most rapidly warming regions on Earth; annual temperatures there have increased by up to 0.56°C per decade since the 1950s. There they found a moss bank that has been slowly growing at the top surface and accumulating peat material since it first established in about 1860. By analyzing core samples of that moss bank, they were able to characterize the growth and activity of the moss and microbes over time. 


The annual melting of sea ice in the Arctic is approaching its yearly "minimum," the time when the floating ice cap covers less of the Arctic Ocean than at any other period during the year, and there is some good news -   this year's summer low is not going to be too bad. 

The concerning news is that this year's melt rates are in line with the sustained decline of the Arctic ice cover observed by NASA and other satellites over the last several decades.


A recent review of research on the response of plants, marine life and animals to declining sea ice in the Arctic found that sea ice decline and warming trends are changing the vegetation in nearby arctic coastal areas.


The Earth has periodic ice ages - every 100,000 years, give or take, and the ice ages last far longer than the warm periods.

In the last century, scientists determined that Earth's ice ages were determined by the wobbling of the planet's orbit, which changes its orientation to the sun and affects the amount of sunlight reaching higher latitudes, particularly the polar regions. The Northern Hemisphere's last ice age ended about 20,000 years ago and then the ice age in the Southern Hemisphere ended about 2,000 years later, suggesting that the south was responding to warming in the north.

 But new research says that Antarctic warming began at least two, and perhaps four, millennia earlier than previously thought.


A year-round ice-free Arctic Ocean surface could explain why the Earth of the Pliocene Epoch had the levels of carbon dioxide in the atmosphere that we have today, but we remain 3 to 9 degrees cooler than the Earth was then.


A new projection estimates that by the middle of this century there could be an average 56 percent drop in the amount of water stored in peak snowpack in the McKenzie River watershed of the Oregon Cascade Range -   if there is a 3.6 degree Fahrenheit temperature increase.

Similar impacts may be found on low-elevation maritime snow packs around the world.


Scientists using tracking data from Garwood Valley in the McMurdo Dry Valleys region of Antarctica have documented an acceleration in the melt rate of permafrost - ground ice - in a section of Antarctica where the ice had been considered stable.

The melt rates are comparable with the Arctic, where accelerated melting of permafrost has become a regularly recurring phenomenon, and the change could offer a preview of melting permafrost in other parts of a warming Antarctic continent, says Joseph Levy, a research associate at The University of Texas at Austin's Institute for Geophysics.

The paper in Scientific Reports


Shrinking sea ice cover in the North Atlantic - baby harp seals impacted most.

A new paper says satellite images have allowed researchers to gauge the relative roles that genetic, environmental and demographic factors such as age and gender may be playing in harp seal stranding rates along the U.S. and Canadian east coasts in recent years.  Recent warming in the North Atlantic gets the blame, according to the paper by advocacy group the International Fund for Animal Welfare and Duke University. 


A potential barrier to deep Antarctic circumpolar flow until the late Miocene?