Arctic Sea Ice Reaches its Minimum Extent for 2016

Advertisment
  • Arctic sea ice extent as measured on September 10, 2016. The orange line shows the 1981 to 2010 median extent for that day. The black cross indicates the geographic North Pole. Image Credit: National Snow and Ice Data Center

    Arctic sea ice extent is usually at its greatest in March and is at its smallest in September. Credit: National Snow and Ice Data Center

    The graph shows Arctic sea ice extent for this year (blue line) compared with four other record low years. Credit: National Snow and Ice Data Center

  • Arctic Sea Ice Reaches its Minimum Extent for 2016
    24.09.2016 16:12

     

    Measurements taken a couple of weeks ago and analysed by the National Snow and Ice Data Center (NSIDC) show that this year’s Arctic sea ice minimum has now been reached. The sea ice in the Arctic alters through the seasons, reaching maximum coverage around March then melting through the northern hemisphere summer to reach a minimum during September-time.

    The 2016 sea ice coverage minimum was discovered as being joint second lowest on record (measured by satellite over the last 37 years), tied with 2007. The lowest ever Arctic sea ice coverage minimum was recorded in 2012 and the top 10 lowest minimum Arctic sea ice extents have all occurred in the 21st century.

    NSIDC believe that the 2016 sea ice extent was much lower than average,  partly due to a much thinner-than-usual ice pack, following the 2015-16 Arctic winter. It is also thought that summer weather conditions played a role on the ice extent. The weather this summer has in general been rather cool, cloudy and stormy across the Arctic. This meteorological trend usually suppresses sea ice melt. However, the potency of two particular storms in August appear to have actually accelerated sea ice melt, through wind and wave action, helping breaking up the ice sheet then transferring fragmented pieces of ice in to warmer waters, where it was able to melt. NSIDC have also seen in previous studies, that accelerated ice melt is possible in particularly stormy spells during the summer as warmer waters from below come to the surface, acting upon the floating ice sheet. Whether this was another contributing fact this summer is still under investigation.

    Research continues on how the extent of sea ice affects climate, not just within the Arctic Circle but further afield too. Sea ice plays an important role on ocean circulation, which in turn is strongly linked to weather patterns on a global scale.

    Some theories suggest that as an increase in sea ice melt dilutes the salty ocean with fresh water, which of course is what ice consists of. Fresh water is less dense than saline water. This in turn could potentially alter global thermohaline (temperature and salinity-driven) circulation or currents in the ocean thus having a large impact on weather patterns and climate. Here in the UK for example, the relatively warm Gulf Stream helps keep us generally quite mild during the winter time but should this warm flow of water weaken, so there is the potential for us to experience chillier winters.

    Sea ice cover can also have a more direct impact on atmospheric circulation patterns. The ice itself acts as a blanket, reflecting sunlight back in to the atmosphere and helping maintain lower temperatures in the Arctic region. When, there is less sea ice, more ocean is left exposed. The relatively dark ocean surface is able to absorb greater amounts of solar radiation, raising the sea’s temperature.  Computer models suggest that this has a limited impact during the spring and summer but during the autumn and winter, can result in stormier conditions in parts of the Arctic. Additionally, there are some suggestions that this scenario can impact the jet stream, thus affecting the weather across a far-larger part of the globe. In the northern hemisphere, the jet stream – a narrow band of fast-moving air in the upper atmosphere – could weaken with extensive sea ice melt and in turn, meander more than usual. With the jet stream tending to be the driving-force behind our weather at the surface, it could be that we see more in the way of a blocking pattern occur, such that drier, colder conditions tend to become locked in place across one part of the hemisphere, whilst in another area, wetter, windier weather dominates.

    Research in to the affects sea ice has on weather patterns is still in its infancy. Even so, there are already patterns emerging, which show direct links to weather and the behaviour of Arctic sea ice.

     

    By: Gareth Harvey