Marine Heatwave and Cold Spell Metrics for Australian Coastal Waters

IMOS - AusTemp provides marine heatwave (MHW) and marine cold spell (MCS) monitoring metrics for the Australian coast from January 1, 2012. It uses the SSTAARS daily climatology baseline and applies 90th-, 50th-, and 10th-percentile thresholds to classify events, also including Sea Surface Temperature anomalies (SSTa) and Degree Heating-Days (DHD) metrics. The dataset supports high-detail mapping of thermal stress events for ecological impact assessment.

Use Cases

• Classify marine heatwave (MHW) and marine cold spell (MCS) categories using SSTAARS 90th-, 50th-, and 10th-percentile thresholds for Australian coastal monitoring.
• Calculate and analyze Sea Surface Temperature anomalies (SSTa) by comparing current SST to a monthly SSTAARS climatology for trend detection.
• Accumulate Degree Heating-Days (DHD) metrics from daily positive SSTa to quantify cumulative thermal stress for coral bleaching risk assessment.
• Map spatial coverage of MHW events using the improved GeoPolar MultiSensor L3S product which adds Himawari-8/9 data to fill SST gaps from cloud cover.

Strengths

• Derived from the operational satellite-derived MultiSensor Level 3 Super-collated (MS L3S) sea surface temperature product, providing a reliable data source.
• Uses the SSTAARS daily climatology baseline (Wijffels et al., 2018), an established reference for developing heat-stress metrics.
• The GeoPolar MultiSensor L3S product adds geostationary Himawari-8/9 data, providing significantly improved spatial coverage and an additional 20% data on average over the MS L3S product.

Limitations

• Data availability is affected by cloud cover; grid cells are left blank when SST cannot be calculated, creating spatial gaps.
• The dataset consists of derived metrics and visualizations (PNG, PDF, HTML) rather than raw tabular data, limiting direct numerical analysis.
• Temporal coverage begins in 2012, which may not capture long-term climatological baselines compared to longer historical records.

Provenance

Source

Australian Ocean Data Network, following on from the Bureau of Meteorology's decommissioned ReefTemp Next Generation product.

Collection Method

Satellite-derived, night-time-only MultiSensor Level 3 Super-collated (MS L3S) sea surface temperature product, with thresholds applied from the SSTAARS daily climatology.

Time Range

From January 1, 2012 onwards.

Freshness

Data is updated operationally, with a last recorded update on 2026-03-21.

Geography

Australian coastal waters.