Waters around Murihiku Southland are heating up faster than almost anywhere else in the country, raising serious concerns for the region's coastal fisheries and marine environments.
The issue was laid out in a November report from acting Environment Southland chief executive Rob Phillips, who drew on the organisation's recent state of the environment report. Phillips noted that sea surface temperatures across New Zealand were rising around 34 percent faster than the global average.
Beyond Fiordland, Southland is experiencing some of the most rapid warming rates in the country. Over the past decade, average temperatures in the region have climbed by 0.4 degrees. Phillips acknowledged there may be a superficially appealing side to this trend. "While it may mean that the region can enjoy some warmer swimming temperatures, continued increases will have detrimental effects on a wide range of our coastal ecosystems, including valued fisheries and habitats."
Council general manager of science Karen Wilson elaborated on the mechanics behind the numbers, explaining that the ocean functions as a vast heat sponge, soaking up excess warmth from the atmosphere and buffering against sharp rises in air and land temperatures. Warming seas feed into more intense extreme weather events while also contributing to sea level rise.
"Rising temperatures can also disrupt ocean chemistry and nutrient cycles, altering major currents and threatening marine ecosystems," Wilson said.
Wilson pointed to coral bleaching, potential food security problems, and shifting habitats for marine mammals as among the outcomes that could follow from sustained ocean warming.
Wilson noted that ocean temperatures do not move in a straight line. Fluctuations driven by El Niño and La Niña cycles, shifting ocean currents, and longer-term climate patterns all play a role. "These natural influences combine with broader climate changes and drive the warming we are observing today," she said.
The 0.4 degree average temperature increase recorded over the past decade applies not only to Southland's waters but also to the east coast of the South Island.
