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Global marine heat waves: frequency, classification and distribution from 1996-2020
Chauhan, A.; Mariani, P.; Technical University of Denmark (DTU), Denmark; (2023): Global marine heat waves: frequency, classification and distribution from 1996-2020. https://marineinfo.org/id/dataset/8235

Availability: Creative Commons License This dataset is licensed under a Creative Commons Attribution 4.0 International License.

Notes: This dataset is under moratorium until 2026-05-06.


This dataset comprises the global frequency, classification and distribution of marine heat waves (MHWs) from 1996-2020, in Chauhan et al. 2023 (https://doi.org/10.3389/fmars.2023.1177571). The classification was done based on their attributes and using different baselines.

Daily SST values were extracted from the NOAA-OISST v2 high-resolution (0.25°) dataset from 1982-2020. MHWs were detected using the method presented by Hobday et al. 2016 (https://doi.org/10.1016/j.pocean.2015.12.014), and by using the 95th percentile of the accumulated temperature distribution to flag the extreme events. A shifting baseline of 8-year rolling period was selected between the years 1982-1996, since this period shows relatively stable maximum values of temperature across different ocean regions. The shifting baseline aims to account for the decadal changes of westerly winds, temperatures and ocean gyres circulations.

The classification was done using the KMeans clustering algorithm to identify the relevant features of MHWs and classify them into separate groups based on feature similarities. This algorithm takes MHW features, namely duration, maximum intensity, rate onset and rate decline, as input vectors and applies clustering in the 4-dimensional feature space where each data point represents an MHW event. Note that all the MHWs features are standardized because unequal variances can put more weight on variables with smaller variances. 

This record comprehends the geospatial datasets of: 

  1. Average number of MHW days per year (i.e., the sum of all MHW days divided by the total number of years, 1996-2020).
  2. Average cumulative intensity per year (i.e., the sum of cumulative intensity divided by the total number of years, 1996-2020).
  3. Total number of MHW events across the different periods averaged on the total number of years (1989-2020). The period 1982-1988 was only used as an initial baseline without calculating MHWs.
  4. Spatial distribution of three MHW categories: moderate MHWs, abrupt and Intense MHWs and extreme MHWs; displaying the total number of MHW days normalized by the number of years considered (i.e., 1989-2020).
  5. Distribution of Extreme MHWs across the different periods (A) 1989-1996, (B) 1997-2004, (C) 2005-2012, (D) 2013-2020. The relative frequency (γ) is a ratio of extreme MHWs in a specific period and all extreme MHWs in the same cluster for all periods. 

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 862428 (MISSION ATLANTIC).

Marine/Coastal, Climatology/Meteorology/Atmosphere, Data not evaluated, Global, Metadata conformant, NetCDF (Network Common Data Form), No limitations to public access, Oceanographic geographical features, Oceans, WGS84 (EPSG:4326), World Oceans

Geographical coverage
World Oceans [Marine Regions]

Temporal coverage
1 January 1996 - 31 December 2020

Technical University of Denmark (DTU), moredata creator

Mission Atlantic, more

Based on this dataset
Chauhan, A. et al. (2023). Distribution and impacts of long-lasting marine heat waves on phytoplankton biomass. Front. Mar. Sci. 10: 1177571. https://dx.doi.org/10.3389/fmars.2023.1177571, more

Data type: GIS maps
Metadatarecord created: 2023-03-17
Information last updated: 2024-06-05
All data in the Integrated Marine Information System (IMIS) is subject to the VLIZ privacy policy