Tad Pfeffer and Mark Meier study a glacier on Ellesmere Island
Tad Pfeffer and Mark Meier at Eureka, Ellesmere Island
in 1989. Photo: Tad Pfeffer.

Melting glaciers and small ice caps will raise sea levels by four to 10 inches over the next century — possibly making the largest contribution to changing ocean levels as the globe continues to warm.

An international team of scientists calculated the contributions from melting glaciers, containing only about 1 percent of the volume of the great ice sheets in Greeland and Antarctica. They reported their results this week in the journal of Science as a cautionary tale.

“Small glaciers and ice caps, not the polar ice sheets, will contribute the majority of sea level rise caused by ice melting by 2100,” researchers report. Most sea-level researchers have focused on the massive polar ice sheets of Greenland and Antarctica because they contain the overwhelming majority of frozen water. But this study, led by Mark F. Meier, the scientists “found that glaciers could contribute 60 percent, or 10 to 25 centimeters, of the total contributions to sea level rise from melting ice.”

Melt them all of these glaciers down to rock — something worth contemplating because mountain glaciers and ice caps all exist in vulnerable environments — and they could raise sea levels by almost 40 inches.

“Disintegrating glacier ice constitutes a significant and accelerating cause of global sea-level rise,” Meier and seven co-authors wrote in “Glaciers Dominate Eustatic Sea-Level Rise in the 21st Century.”


Here’s the abstract:

Ice loss to the sea currently accounts for virtually all of sea-level rise not attributable to ocean warming; about 60% of the ice loss is from glaciers and ice caps rather than from the two ice sheets.

The contribution of these smaller glaciers has accelerated over the last decade, in part due to dramatic thinning and retreat of marine- terminating glaciers associated with a dynamic instability generally not considered in mass balance/climate modeling. This acceleration of glacier melt may cause 0.1-0.25 m of additional sea-level rise by 2100.

Skiers on Worthington Glacier in Alaska
Skiers, Worthington Glacier, 1997.
Photo: Tad Pfeffer

Why focus on the relatively puny glaciers, many concentrated on the fringes of ice sheets and in Alaska?

“They are more susceptible to large decreases in their relative sizes than the two continental polar ice sheets,” the scientists wrote.

The findings bolster studies over the past few years that found Alaskan glaciers were contributing a much larger percentage of sea-level rise than previously thought. Other major contributor to ocean rise is thermal expansion of sea water as it warms.

Of course, all bets slosh from the table if the polar ice sheets start to disintegrate. See the FNS story on the possibility of a “flip” in phase that could trigger a massive, catastrophic meldown of the ice sheets in a matter of decades.

For now, however, scientists should concentrate on what’s happening with the glaciers.

“In order to improve our understanding of the ice melt contribution to sea-level, we must recognize that the (Glaciers and ice Caps), not the big ice sheets, are most important today, and will continue to be important throughout this century,” they wrote.

“While large ice masses may surpass the glacier contribution to sea level rise in the distant future, the (Glaciers and ice Caps) contribution is important now and will be for the remainder of this century.”