Globally, glaciers have been on the retreat for several decades. Between 1983 and 2008, however, at least 58 New Zealand glaciers grew in size.

Scientists have struggled to explain their advance, but new analysis suggest a regional climate anomaly, a period of unusually cold temperatures, encouraged their growth.

"Glaciers advancing is very unusual -- especially in this period when the vast majority of glaciers worldwide shrank in size as a result of our warming world," Andrew Mackintosh, a climate scientist at Victoria University of Wellington's Antarctic Research Centre, said in a news release. "This anomaly hadn't been satisfactorily explained, so this physics-based study used computer models for the first time to look into it in detail."

Mackintosh and his colleagues built a climate model -- populated with data from field observations in New Zealand -- to illuminate the drivers of glacial growth. Their findings, detailed in the journal Nature Communications, suggest a prolonged period of low temperatures, not precipitation, explain the advancing glaciers.

Researchers say heightened regional climate variability is one the byproducts of man-made climate change.

"New Zealand sits in a region where there's significant variability in the oceans and the atmosphere -- much more than many parts of the world," Mackintosh said. "The climate variability that we identified was also responsible for changes in the Antarctic ice sheet and sea ice during this period."

The period of cooling and glacial growth appears to now be over. New Zealand's largest glacier, Franz Josef Glacier, has retreated almost a mile since 2008.

"New Zealand's glaciers are very sensitive to temperature change," Mackintosh said. "If we get the two to four degrees of warming expected by the end of the century, our glaciers are going to mostly disappear. Some may experience small-scale advance over that time due to the regional climate variability, but overall they will retreat."