In late March 2018, scientists from the National Snow and Ice Data Center (NSIDC) and NASA reported that Arctic sea ice had reached its annual maximum extent. Once again, the ice cover was well below average. The four smallest maxima in the satellite record have all occurred in the past four years, continuing a decades-long trend of shrinking ice in the Arctic Ocean and surrounding waterways.

The annual maximum and minimum ice extents for the Arctic region have become steadily smaller over the past 40 years, and the percentage of thick, multi-year ice has been shrinking considerably. This thinning and retreating ice has opened the Arctic Ocean to new opportunities, but also serious environmental concerns. Shipping traffic fits into both categories.

The map above shows the average concentration of Arctic sea ice on March 17, 2018, when it reached the annual maximum. All white-shaded areas had an ice concentration of at least 15 percent (the minimum at which satellites give a reliable measurement), and span a total area that scientists refer to as the “ice extent.” Ice cover peaked at 14.48 million square kilometers (5.59 million square miles), the second lowest maximum on record and 1.16 million square kilometers (448,000 square miles) below the 1981 to 2010 average.

The effects of declining sea ice have rippled throughout the Arctic region and the world. Plants, animals, plankton, and people are being forced to adapt to warmer summers and winters and to more open water. Atmospheric and ocean-circulation patterns are also changing, moving the jet streams and stirring up unusual weather in the high- and mid-latitudes.

The disappearing ice is also changing the shipping industry. In August 2017, a newly designed tanker with a hardened hull became the first merchant ship to sail across the Arctic Ocean without the aid of an icebreaker. The Christophe de Margerie traveled from Norway to South Korea in 19 days, nearly a week faster than the traditional trip through the Mediterranean and the Suez Canal.

It took just six months to top that feat. In February 2018, a tanker carrying liquid natural gas (the Eduard Toll) cruised through mid-winter ice cover from South Korea to Sabetta terminal (northern Russia) to France.

Russia, China, Canada, the United States, and Iceland are leading a flotilla of nations preparing for more shipping activity in the Arctic. The Northwest Passage through Canada and the Northern Sea Route, or Northeast Passage, north of Russia and Siberia are both valued because they could significantly shorten ship transit times between Asia, Europe, and North America. But scientists and environmental advocates have serious concerns about pollution, oil spills, and disturbances to marine life, among other possible impacts. Then there is the danger to the lives of sailors plying icy waters with poor navigation charts.

Whether open Arctic water is a boon for shipping, it remains bad news for the Arctic environment as we have known it. “Arctic sea ice cover continues to be in a decreasing trend, and this is connected to the ongoing warming of the Arctic,” said Claire Parkinson, a climate scientist at NASA’s Goddard Space Flight Center. “It’s a two-way street: the warming means less ice is going to form, and more ice is going to melt. But also, because there is less ice, less of the Sun’s radiation is reflected off of Earth, and this contributes to the warming.”