Greenpeace declared its Save the Arctic movement boasts a support base of 1.8 million people.
"Here is the moment we must act, to stop the reckless and greedy oil companies and the political leaders who allow them to continue," a statement from a campaigner read. "Wherever big companies break the arctic silence with their oil drills, this movement will be ready to stop them."
Greenpeace trailed drillships contracted by Royal Dutch Shell as the company readied for a campaign offshore Alaska. Encroaching sea ice and problems with a containment dome meant to respond to a potential oil spill led the company to scale back its ambitions for the year.
The National Snow and Ice Data Center in Boulder, Colo., reported the polar ice cap measured about 1.3 million square miles last weekend, 18 percent less than the previous record set in 2007. The NSIDC said low levels of ice coverage were normal for September but added in a statement the record low marked "uncharted territory."
Greenpeace said it was advocating collective action to protect the region, noting lower ice levels are a likely culprit of warmer temperature trends.