Marine Heatwave Analysis

Cockburn Sound — UKMO OSTIA Satellite SST

← Back to Chapter 18: Marine Heatwaves

Overview

Marine heatwaves (MHWs) are prolonged periods of anomalously warm sea surface temperatures that can stress marine ecosystems, trigger coral bleaching, and alter species distributions. This page presents an automated MHW analysis for Cockburn Sound using satellite-derived SST data and the heatwaveR detection framework.

Data source UKMO OSTIA — Cockburn Sound Site 9 (32.18°S, 115.73°E)
Record 01 Oct 1981 – 21 Feb 2025 (43.4 years)
Baseline period 1981 – 2024
Threshold 90th percentile (seasonal)
Events detected 91 events, 1217 total MHW days
I Moderate
II Strong
III Severe
IV Extreme

Sea Surface Temperature Record

Use the range slider below the chart to zoom into specific periods. Hover over MHW events (shaded regions) for details.

Annual MHW Summary

Number of MHW events and total MHW days per year.

MHW Event Intensity

Each point represents a detected MHW event, positioned at the peak date. Point size reflects duration; colour indicates category. Hover for full details.

MHW Event Explorer

Select a year to view the top MHW event for that period with category shading (Hobday et al. 2018). The dropdown defaults to the year with the most intense peak on record.

Event Summary Table

Click column headers to sort. Use the search box to filter events.

heatwaveR logo

Methodology

Detection framework: heatwaveR (Schlegel & Smit 2018), implementing the Hobday et al. (2016) definition.

  1. A seasonal climatology and 90th percentile threshold are computed from the baseline period using an 11-day moving window.
  2. MHW events are detected where SST exceeds the threshold for ≥5 consecutive days (gaps ≤2 days are bridged).
  3. Events are categorised (Hobday et al. 2018) based on exceedance intensity relative to the difference between the threshold and the seasonal climatology.

References

  • Hobday, A.J. et al. (2016). A hierarchical approach to defining marine heatwaves. Progress in Oceanography, 141, 227–238.
  • Hobday, A.J. et al. (2018). Categorizing and naming marine heatwaves. Oceanography, 31(2), 162–173.
  • Schlegel, R.W. & Smit, A.J. (2018). heatwaveR: A central algorithm for the detection of heatwaves and cold-spells. JOSS, 3(27), 821.