New Zealand glaciers disprove global climate sync-up

Researchers have long puzzled over how climate has evolved over thousands of years in different regions of the world.

Has the climate in the northern half of the globe changed in tandem, or in opposition to, the climate in the southern half?

An international group of researchers (including New Zealand scientists) has taken up this question, comparing local glaciers with glaciers in the Northern Hemisphere.

The glaciers offer a treasure trove of climate information and are relatively easy to access. The researchers’ findings, published in Science tomorrow, reveal that global climate evolved differently, with the climate in both hemispheres evolving in sync at times and in opposite directions during other periods.

New Zealand co-authors Dr David Barrell, geologist & geomorphologist at GNS Science, Dr Andrew Mackintosh, Senior Lecturer in Geography and Geology at Victoria University and glaciologist Dr Trevor Chinn comment:

“It has for many decades been suspected that there are differences in glacier behaviour between the northern and southern hemispheres, and we were expecting to find some contrasts. What
exactly those contrasts would be we did not know.

“This new dating provides the first direct confirmation of these earlier suspicions about climate patterns, and provides far more detail on glacier movements than was known before.  The earlier work was hindered by a lack of methods for dating moraines. The development and improvements in dating technology represent the main break-through of this work.”

From a commentary piece in this week’s Science by Dr Greg Balco, from the Berkeley Geochronology Center in Berkeley, California:

“Schaefer et al. come to the unexpected conclusion that neither hypothesis explains the full data set: Sometimes glaciers in New Zealand were larger than at present when those in the Alps were smaller, but at other times both appear to have advanced simultaneously. The answer to the question “were Holocene glacier advances in the Northern and Southern Hemispheres in phase, or out of phase?” turns out to be “no.”

“This answer satisfies advocates of neither hypothesis. Instead, it highlights the challenge – and the opportunity-of better reconciling paleoclimate data, such as glacier advances and retreats, with advances in glacier modeling and modern climate dynamics.”

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