American plants don’t forget their origins
The ecological characteristics of plants in Panama can be explained by their evolutionary development millions of years ago, according to researchers from the University of Michigan.
By using an ecological evolution model, the scientists have shown that the plant characteristics are strongly linked to their geographical past.
Millions of years ago an ocean separated the continents of North and South America so the two land masses had very different climatic and biological characteristics, and different species evolving on each. Approximately 3 million years ago, these land masses became connected by what is today Central America, which led to the migration and mixing of previously distinct plant and animal communities, in what is known as the Great Biotic Interchange.
The research has shown that certain plant species retain the ancient ecological traits from before the Interchange, even millions of years after the species’ dispersal onto new lands.
Chain reaction caused Antarctic breakup
In a Glaciology meeting held this month in Beijing, geophysicist Douglas MacAyeal suggested that the unexpected collapse of the Larsen B ice shelf in Antarctica in 2002 was due to a chain reaction of fractures around the ice.
Larsen B had been slowly melting away for decades, forming thousands of lakes on the ice shelf. MacAyeal and his team used a mathematical model to show that when the water of one lake was drained, the removal caused ice fracturing in nearby lakes. These fractures then drained neighbouring lakes and caused more fracturing. The effect snowballed and weakened the ice structure around the shelf.
The researchers concluded that the lake draining and ice fracturing chain reaction is the likely cause of the eventual sudden breakup of the ice shelf.
Ozone hole could be warming planet
A new study conducted by scientists from the Lamont-Doherty Earth Observatory at Columbia University suggests that the ozone hole might slightly warm the Earth’s climate.
These results go against the previously held view that the ozone hole had a small cooling effect on the planet.
The team, led by climatologist Kevin Grise, investigated the effects of the ozone hole on the jet stream, an air current flowing around the South Pole. They found that every time the ozone hole appeaed during spring months, the jet stream systematically showed a southern shift during the subsequent summer months, which dragged high and mid-level clouds along with it.
These high and mid-level clouds reflect incoming solar radiation back out to space. As less solar radiation reaches the poles than the tropics, a poleward shift in cloud cover results in a reduced reflector effect, and therefore an accompanying increase in incoming solar radiation and so warming in the tropics.
IMAGE: Wikicommons, NASA