NIWA’s Sea Surface Temperature Update
A fortnightly report, updated over summer, covering sea surface temperatures and anomalies (differences from average)
around New Zealand. Following the Tasman Sea marine heatwave event of 2017-18, this report will help users understand
the latest conditions in the ocean and their expected changes over the upcoming weeks.
Recent Sea Surface Temperatures and Anomalies
Over the past two weeks, the average sea surface temperature (SST) anomaly in the New Zealand region (as above) was
0.74°C above the long-term 1981-2010 average. SSTs are much warmer than average around the South Island and to the west,
south, and east of the country. Meanwhile, SSTs are closer to average near Northland and more broadly to the north of
the country. While SSTs are generally warmer than average, they are markedly cooler than this time last year when a
marine heatwave event was underway.
Expected Conditions over the Next Several Weeks
The change in SST over time is linked to circulations in both the atmosphere and ocean. From this weekend into early
next week, a large ridge of high pressure is expected to bring above average air temperatures and sunshine to the New
Zealand region, which will likely lead to some short-term SST warming. After a brief unsettled, cooler period, higher
pressure than normal is favoured over the Tasman Sea from late December into early January, which may encourage
additional warming. Generally speaking, SST anomalies are expected to be similar or warmer over the coming weeks.
Background:
Sea Surface Temperature Update is a fortnightly report for New Zealand media. It provides measurements of sea surface
temperature and anomalies (differences from average) measurements for New Zealand coastal and Tasman Sea waters.
Sea surface temperature anomaly: the difference between the long-term (1981-2010) average sea surface temperature and
current sea surface temperature for a given time of year.
New Zealand region: within this document it refers to the ocean region bounded by the coordinates (145°E-175°W, 25-55°S)
SST: abbreviation for sea surface temperature.
Marine heatwave: periods of extremely warm sea surface temperature that persists for a prolonged period of time and can
extend up to thousands of kilometres.