Will Melting Arctic Ice Provide a Silver Lining for Shipping's Emissions?

A melting Arctic is prompting questions about climate change, geopolitics, and security among other topics, yet one question receiving more attention lately is steeped in nautical mythology: fabled Arctic shipping passages.

Typically relegated to the Indian, Pacific and Atlantic Oceans, with various passages in between (Suez and Panama Canals, Malacca Strait, etc.), the Arctic Ocean may present passages that could drastically reduce shipping distances -- some of which are already being traversed -- and by virtue, reduce time, cost, fuel consumption and greenhouse gas (GHG) emissions.

Could this be a silver lining to our warming planet? Savings in time and cost go without saying, but do the GHG emissions savings reaped by an open Arctic offset those emitted by the melting of the Arctic itself? While the direct emissions saved from Arctic shipping may be significant in the context of shipping emissions overall, the net emissions scenario of an open Arctic are unlikely to offset the warming Arctic -- not by a long shot -- and here's why:

According to the International Maritime Organization, as of 2007, annual CO2 emissions from shipping were 870 million tons, or 2.7 percent of annual global CO2 emissions. Estimates of methane hydrates on the Arctic seabed (PDF), on the other hand, range from the thousands to tens of thousands gigatons of methane. As the Arctic waters warm, methane, which has approximately 20 times the global warming potential (GWP) of CO2, is released from the melting hydrates, which have long been trapped in ice crystals. Both the quantity and GWP of methane is what accounts for the Arctic's potentially tremendous impact on climate change.

Let's take a closer look at the potential damage that could result from a warming Arctic. A recent study looked at methane seeping from the shallow Siberian shelf -- one of several Arctic Ocean coastal shelves -- which covers more than 580,000 square miles. In multiple locations where "methane chimneys" are forming, methane levels are up to 100 times the normal level in the surrounding water. The imbalance is even visible via gas bubble clouds rising to the surface (another study over 20 years found similarly alarming methane release in the East Siberian Arctic Shelf).

If the Siberian shelf melts completely and unlocks the methane from its icy tomb, it is estimated to potentially release 12 times the current atmospheric level of methane. Thus, the potential methane release from the Siberian shelf alone, not including other Arctic continental shelves, could be nearly 800 times more GHG emissions than 2007 annual shipping emissions. Fears of a "methane time bomb" from land-based permafrost are not new, but the fear of a potential methane depth charge in the Arctic is gaining increasing attention. Credit: Zina Deretsky, National Science Foundation