A new ice core, drilled in West Antarctica suggests that the Southern Hemisphere, and not the Northern Hemisphere began warming first at the end of the last ice age, approximately 20,000 years ago.
Up until now, it was believed that deglaciation, at the end of the last glacial maximum, around 20,000 years ago was initiated by the Northern Hemisphere. Now, to anyone not involved in palaeoclimatology, you might be asking why it even matters, as long as things started to warm up. Understanding the drivers of deglaciation is important, as it provides us with an understanding of the way that climate works.
Most palaeoclimate stories call on the Northern Hemisphere, and in particular, the North Atlantic to initiate changes. The Southern Hemisphere, and Antarctica, has traditionally been viewed as a slave to the North Atlantic, only responding to changes, but not initiating them.
This idea causes some problems for people like me, working in the Southern Hemisphere on past changes in climate. It means that we rely on the North Atlantic to drive the changes we observe, even if the mechanisms by which it would have to travel from the North Atlantic don’t make a lot of sense. Climate anomalies are required to travel halfway across the world to impact on our results. For me, this is not a huge problem, since I work on a site quite close to the equator, and it actually does make sense that North Atlantic climate signals could effect this area. People working in Tasmania, for example, find the whole thing much more problematic.
But finally, the Southern Hemisphere is getting some of the credit!!
A new ice core drilled in West Antarctica suggests that it was in fact the Southern Hemisphere, and Antarctica which began to warm and end deglaciation. Previous ice cores that have been drilled were from East Antarctica, which is a much colder and more remote site than West Antarctica. These ice cores showed a delay in warming until after the Northern Hemisphere.
But, as we know, the West Antarctic is much more sensitive to global changes (as shown by its current rate of melting due to climate change, compared to an increase in ice seen in East Antarctica), and may in fact provide a more accurate account of the true sensitivity of Antarctica.