You may have already seen the charts compiled by Antarctic ice cores, a kind of a cardiogram ice ages. If Yes, then most likely you said cyclicality: about thousand years of glaciation, then a relatively short interglacial period, and again gradual cooling covers the planet. The reason - in a small and rhythmic variations of the Earth's orbit, which alter the amount of sunlight received our home.

Climate scientists, however, have noticed a number of oddities in the following graphs. Why hundred thousand years? Indeed, there orbital cycle, which occupies so much time, but there are others: one placed about 20 thousand years, and one in 41 thousand And then statisically cycle really changes things less than others. So why is he manages the beating of the icy heart of the Earth?

Offered a lot of good answers to this question, but there is another mystery. Worth a look for a million years into the past, and ECG changes. Is becoming the norm cycle in 41 thousand years. Here, too, there are several hypotheses, but check them was difficult due to lack of data.

Some gaps were able to compensate to a new study conducted by the staff of the University of Cambridge (UK). They reconstructed 1.5 million years of climate history, recorded in marine sediments off the East coast of New Zealand. As is customary in such cases, the researchers measured the composition of oxygen isotopes in the carbonate shells of single-celled foraminifera.

The matter is complicated by the fact that the isotopes of oxygen in these "sinks" respond to various factors. On the one hand, the ratio of the isotopes in the ocean is changing due to water freezing in the continental ice sheets and the lowering of the sea level. On the other, the sea water temperature also affects the chemical composition of shells of foraminifera.

To sort out this mess, usually looking for a "sensor"that would codify temperature alone. Here in this role gave the ratio of magnesium to calcium magnesium can take the place of calcium carbonate shells). If you subtract the signals related to temperature changes, will only have data about the volume of ice.

The method is not new, but it almost for the first time managed to apply to the glacial cycles, covering 41 thousand years, not 100 thousand Previous research that could not distinguish between the impact of temperature change from the reduction in sea level, talked about the fact that the transition was carried out gradually: over 500 thousand years periods of glaciation was becoming more and more cold. But according to new data, there was a sudden leap in the volume of ice, which peaked about 900 thousand years ago. Since then, the ice ages adhere stotysyachnogo cycle.

This is the explanation of transition to the new regime. Reaching a certain size, ice sheets become more sustainable, since the nodes in the glaciers are at high altitude, where the temperature is lower than on the surface of the planet. That is why ice sheet to withstand the orbital shocks to warming, which are characteristic of the cycle in 41 thousand years.

Previous research was concentrated on the North Atlantic. As the new data is different from previous results, it makes sense to assume that the Antarctic ice sheet has not kept pace with the Northern hemisphere.

And there is every reason to think that the Antarctic "switched" to the Ground. In the southern hemisphere, the increase in the number of incoming solar radiation at the end was the last 41-year period was very weak, which allowed the ice of Antarctica to avoid the usual melting, and then grow to a new high.