Arctic ice melting faster than predicted

The rate of sea-ice decline has accelerated and the decline rate in the past 10 years has been higher than the Intergovernmental Panel on Climate Change predicted in 2007, the report says.

"Evidence from lake sediments, tree rings and ice cores indicates that Arctic summer temperatures have been higher in the past few decades than at any time in the past 2000 years," the report says. "Previously unseen weather patterns and ocean currents have been observed, including higher inflows of warm water entering the Arctic Ocean from the Pacific."

Temperatures in the Arctic permafrost have risen by up to 2 degrees C in the past two to three decades, and the southern limit of the permafrost has been moving north, with the limit having retreated by 80 miles in past 50 years in the Canadian province of Quebec, for example, the report says.

Most Arctic glaciers and ice caps have shrunk in the past 100 years, especially in Canada and southern Alaska. Climate models predict a 10 to 30 percent drop in the mass of mountain glaciers and ice caps by the end of the century, with the melting of the Greenland ice sheet expected to accelerate.

Overall loss of snow and ice cover will likely heighten the warming trend, mainly because the white snow and ice tend to reflect heat from sun, rather than allowing the heat to be absorbed by the darker land or ocean water. Scientists now think that Arctic sea-ice cover will all but disappear in the summer by mid-century.

The absorption of more heat by the sea during the summer, as the ice cover retreats, has already caused an increase in air temperatures in the fall, while in the spring the snow has tended to melt progressively earlier, thus leading to a decrease in the number of winter days with on-land snow cover. On the other hand, the depth of the snow cover has varied between different regions. Climate models predict increases in overall precipitation and snow depths, although higher temperatures and early snow melts will likely lead to some drying out of Arctic land, the report says.

The warming of soils may increase the release of methane and carbon dioxide into the atmosphere, with these greenhouse gases potentially further accelerating the global warming.

The release of freshwater into the Arctic Ocean from melting ice could impact global ocean currents and climate systems, while the release of water from Arctic glaciers, ice caps and the Greenland ice cap could raise global sea levels from between 3 feet and 5 feet by 2100, the report says.

Importance of Agulhas current eddies for the global climate | Deep ...

I’ve been in Brazil for the past week for some research coordination meetings.  This has involved a number of different folks in several forums, but the whole process was pervaded by a patent anxiety on the part of many people I spoke to with regards to climate change.  This is not new of course, but was certainly tinged with renewed shades of urgency because of the lead up to the COP17 meeting in December in South Africa and the RIO+20 meeting next June in Brazil.  The latter will celebrate twenty years since the influential Rio earth summit on sustainable development in 1992 and will revisit progress on many of that meeting’s themes in light of what we now know about climate change, its causes and impacts.

On this trip I was introduced to Dr. Edmo Campos , an ocean and climate modeler at the University of São Paulo.  Edmo and others of his ilk study how the ocean and atmosphere circulate, whether we can make computer models that accurately reflect these circulation patterns and whether those models have useful power to predict future climate patterns or to explore different scenarios that might arise if we go down different climate trajectories.  Edmo showed me one especially compelling slide (the animated gif below) and opened my eyes to an oceanographic phenomenon that shows just how connected seemingly distant parts of the global climate system can be.  It’s called the Agulhas Leakage and it turns out to be one of the most important drivers of global climate that’s been studied in recent times.

To understand what the Agulhas Leakage is (I’ll call it the Leakage from now on) and what it means, it helps to have a bit of background about how the oceans of the world move, because they are not mammoth static lakes, but a complex network of interconnecting currents (Kevin talked about this in his excellent World Oceans Day piece at Scientific American ).  These are what Edmo and others call “rivers within the sea”, criss-crossing streams in the oceans, connecting them all in a giant energy conveyor that moves water warmed by the tropical sun towards the poles along the surface and mixes salts and nutrients down into deeper waters at higher latitudes.  One of the most well-known of these circulation patterns is called AMOC * by oceanographers and includes the Gulf Stream current that is familiar to so many folks who live in North America and Europe.  The Gulf Stream is the current that shoots up the Atlantic coast of the US before arcing across towards the UK, bringing Caribbean warm water to the coasts of western Europe and allowing those countries to have more temperate climates than nations at similar latitudes elsewhere.  There’s more to AMOC though, including giant rotating gyre currents in both the North and South Atlantic, equatorial currents that jet warm water across the ocean basins and the Brazil current that runs southward along the east coast of South America.

Ocean Currents, A Derivative of the Encyclopedia of Ocean Sciences

Environmental Science

Measurement of deep ocean currents with one-shot neutrally buoyant floats

Deep ocean circulation, physical and chemical aspects

Ocean currents