Scientists have known for a long time that ocean currents affect climate. The big unanswered question is how ocean currents change during the periods of greatest change–from ice ages to periods of global warming.
During the Eocene period, 38 million years ago, the Antarctic had a temperate climate. What is now the midwest United States was covered in tropical jungles. The temperature differential during that last warm period was much smaller than it is today, when Antarctica is a frozen tundra.
New research suggests that the Antarctic Circumpolar Current (ACC), an ocean current that surrounds Antarctica, played a major role in the Eocene climate shift and that ACC formation played a vital role in the formation of modern ocean structure. During the Eocene, when temperature differences were not as large between the poles and the midlatitudes, ocean currents were weaker than they are today. Today, the ACC is considered the most significant ocean current, thermally isolating Antarctica from the rest of the planet, keeping warm surface waters away from the frozen ice sheets.
“What we have found is that the evolution of the Antarctic Circumpolar Current influenced global ocean circulation much earlier than previous studies have shown,” said Katz, who is assistant professor of earth and environmental science at Rensselaer. “This finding is particularly significant because it places the impact of initial shallow ACC circulation in the same interval when the climate began its long-term shift to cooler temperatures.”
Just how did this shift in ocean currents happen? That’s not yet understood.
Scientist Miriam Katz points out, “By reconstructing climates of the past, we can provide a science-based means to explore or predict possible system responses to the current climate change.” As always, science requires more study to start filling in the blanks of the big unknowns!
A new study has been published disproving the previous explanation for the end of the Marinoan ice age, also known as “Snowball Earth.” That ice age ended abruptly about 600 million years ago.
The debunked explanation stated that methane bubbled up from the oceans and was consumed by microbes, which released carbon dioxide into the atmosphere, warming the Earth. Earlier scientists had interpreted “bubbles” in the rocks as evidence of the ancient microbial activity.
A new study on those rocks showed that they were formed under very high temperatures–temperatures at which no microbes are known to survive. In addition, better dating of the rocks showed that the “bubbles” were formed millions or tens of millions of years after the end of the ice age.
So scientists still don’t have an explanation for the end of “Snowball Earth.” But they do know a couple of things that didn’t cause the end of the ice age.
As scientists come up with new explanations for the end of the ice age, those explanations will be tested by other scientists. When explanations can be disproved with evidence, science moves forward. We may never discover the true cause of the end of “Snowball Earth,” but one thing’s for sure–we’ll know a lot more about how the Earth works by trying to craft a good explanation. That’s the way science works!
The Earth is getting warmer. In warmer climes, decomposition occurs more quickly. This releases more carbon dioxide into the atmosphere, leading to further warming. But it needn’t get completely out of control–trees (and other plants) can come to the rescue!
A recent study in a central Massachusetts forest has shown that increased temperatures do indeed lead to increased decomposition. But they also led to increased tree growth, partially offsetting the carbon dioxide release from decomposition. Why? The researchers found that nitrogen was also being liberated by the decomposition.
Because tree growth is limited by the availability of nitrogen, an increased supply of nitrogen results in increased growth. The trees’ growth spurts result in some of the carbon dioxide being stored in the wood rather than being released into the atmosphere. Unfortunately, the trees don’t take in ALL of the released carbon dioxide… trees to the (partial) rescue!