Arctic sea ice is in the midst of a record-breaking melt season. This is yet another symptom of human-caused climate change progressing much faster than scientists anticipated.
Every year, the frozen surface of the Arctic Ocean waxes and wanes, covering the largest area in February or March and the smallest in September. Over the past few decades, these September minima have been getting smaller and smaller. The lowest sea ice extent on record occurred in 2007, followed closely by 2011, 2008, 2010, and 2009. That is, the five lowest years on record all happened in the past five years. While year-to-year weather conditions, like summer storms, impact the variability of Arctic sea ice cover, the undeniable downward trend can only be explained by human-caused climate change.
The 2012 melt season started off hopefully, with April sea ice extent near the 1979-2000 average. Then things took a turn for the worse, and sea ice was at record or near-record low conditions for most of the summer. In early August, a storm spread out the remaining ice, exacerbating the melt. Currently, sea ice is significantly below the previous record for this time of year. See the light blue line in the figure below:
The 2012 minimum is already the fifth-lowest on record for any day of the year – and the worst part is, it will keep melting for about another month. At this rate, it’s looking pretty likely that we’ll break the 2007 record and hit an all-time low in September. Sea ice volume, rather than extent, is in the same situation.
Computer models of the climate system have a difficult time reproducing this sudden melt. As recently as 2007, the absolute worst-case projections showed summer Arctic sea ice disappearing around 2100. Based on observations, scientists are now confident that will happen well before 2050, and possibly within a decade. Climate models, which many pundits like to dismiss as “alarmist,” actually underestimated the severity of the problem. Uncertainty cuts both ways.
The impacts of an ice-free Arctic Ocean will be wide-ranging and severe. Luckily, melting sea ice does not contribute to sea level rise (only landlocked ice does, such as the Greenland and Antarctic ice sheets), but many other problems remain. The Inuit peoples of the north, who depend on sea ice for hunting, will lose an essential source of food and culture. Geopolitical tensions regarding ownership of the newly-accessible Arctic waters are likely. Changes to the Arctic food web, from blooming phytoplankton to dwindling polar bears, will irreversibly alter the ecosystem. While scientists don’t know exactly what this new Arctic will look like, it is certain to involve a great deal of disruption and suffering.
Daily updates on Arctic sea ice conditions are available from the NSIDC website.