In the same way, the Antarctic Peninsula has been warming steadily. At the South Pole, temperatures recently have dropped as low as minus 77 degrees, the coldest there in 40 years. At the other end of the planet, the amount of sea ice in Arctic waters is shrinking annually, and the ice is as much as 40 per cent thinner. Still, for all the change, no one knows precisely what to blame. It could be higher temperatures or altered ocean currents - perhaps variations in cloud cover, solar radiation and atmospheric chemistry.
Greenhouse gases no doubt play an important role.
It could be some subtle recipe of time and the natural rhythm of the ice itself. The breakthrough in this decade is the ability to see these changes. They are revelations. The breakthrough in the next decade will be the ability to understand them. Mr MacAyeal approached B15A in the Ross Sea for the first time earlier this year aboard the US Coast Guard icebreaker Polar Sea.