You have arrived at the Marine Heatwave (MHW) Tracker. This web application shows the occurrence of MHWs around the world in near-real-time (roughly a one-two day delay). The Tracker also shows the historic daily records for the whole planet going back to January 1st, 1982. It is also possible to look at the current and historic records for Marine Cold-Spells (MCS). Please see the 'How do I use this?' section below for details.
A MHW is generally defined as when the temperature in a given location is in the top 10% of temperatures recorded during that time of year for at least 5 straight days. For example, if the coastal waters off Durban in South Africa are roughly 22°C on any given April 1st, if temperatures in excess of perhaps 28°C are recorded there in 2019 over March 28th to April 10th, this could be flagged as a MHW. This is a definition for MHWs first put forward by Hobday et al. (2016) . For a more detailed explanation with visuals please follow this link . An interactive demo for how to detect a MHW is available at this link .
In the map panel of the Marine Heatwave Tracker we can see that there is a particular colour palette being used. Each of these four colours corresponds to increasing categories of MHWs as first proposed in Hobday et al. (2018) . The first category, 'I Moderate', is somewhat common and no category one MHWs have yet been recorded as causing lasting ecological or financial damage. The second category of MHWs, 'II Strong', are increasing in occurrence the most rapidly of the four categories and are on course to become as common as category one MHWs were when record keeping began in the 80's. Fortunately, category two MHWs have rarely been documented to cause lasting damage. The third category, 'III Severe', are less common but can be devastating when they persist for more than a month. The last category, 'IV Extreme', is thankfully a rare occurrence. It is known that less than three months of a persistent category four MHW can wipe out entire coastal ecosystems. If we switch the map layer to MCSs we will see a fifth category 'V Ice'. This was an addition to the category naming convention from Schlegel et al. (2021) . This category shows when a cold event is being detected at a threshold below -1.7°C. This basically means we are just looking at ice that is a bit colder than normal. Not really a proper MCS by the intended spirit of the definition.
If you've found your way to this website then you are likely interested in the effects we are having on the worlds oceans and probably have your own personal reasons to care about their health. There are many anthropogenic (human caused) threats to the health of the oceans, which include but are not limited to: over-fishing, chemical run-off from land, and climate change in the form of extreme warm water events known as MHWs. All of these different threats may impact the ocean in different ways, but one of the main concerns is that we are changing the oceans so much that we will not be able to repair them ourselves. MHWs are not new to our oceans, but our ability to quantify them and put them up on a website like this is. Thanks to this tool we can now see for ourselves in near-real-time where in the world extreme temperatures may be threatening the parts of the oceans where we work, live, and play. It is our hope that this website can be used around the world to help anyone that is interested to see if the changes they have noticed in their ocean are due to a MHW or not.
This site works similarly to the Google maps we use in day-to-day life. Click and drag to move around the world. Use the mouse scroll wheel, or +/- buttons, to zoom in or out. The 'Date' box in the 'Controls' panel tells us which date is being shown on the map. Clicking in this box we can choose any date from the near present back to January 1st, 1982. Click on 'Map layer' to bring up the options for which type of data to visualise. Curently one may choose between daily MHW or MCS data. Please see the 'What are these different map layers?' section below for more detail. Click on the 'Map data' button to download data for the chosen map layer over a range of dates. Note that downloads are limited to 62 days of data. To disable white ice mask on the map, click on 'Ice mask' and toggle the switch off.
If one of the pixels on the map catches your eye, clicking on it will give more information in the window below the map. There we can find three panels. The first, 'Time series', shows the daily data for the pixel we clicke don. Using the 'Date range' selector we can extend the time period we want to display. The second tab, 'Lolliplot', shows all of the MHW/MCS in the selected date range, but focuses on just the events. This plot is interactive and we can move our mouse over the points to see more info. Lastly, the 'Table' tab shows the metrics for all of the events in the chosen date range. We can sort the events by clicking on the different columns. We can download the climatology & threshold data as well as the MHW/MCS data for the chosen pixel with the download buttons at the bottom of the control panel. To download the temperature data please go to the NOAA website .
The global satellite product used in the Marine Heatwave Tracker is the daily Optimally Interpolated Sea Surface Temperature (OISST) v2.1 data on an even 1/4 degree grid that may be downloaded from the National Oceanic and Atmospheric Administration (NOAA). The daily values go back as far as September 1st, 1981, but the MHW Tracker only hosts results starting on January 1st, 1982 as this is the first full year of data. More information about these data may be found here .
Please note that the data are released in near-real-time, and then go through a second layer of quality control that takes roughly two weeks. Therefore any MHW results shown in this app within two weeks of the current date may be subject to minor changes. All MHW results older than two weeks may be taken as final. In practice, the difference between the preliminary results and the final results are almost always negligible.
The MHW/MCS results on the Marine Heatwave Tracker are calculated with the R version of the Hobday et al. (2016, 2018) definition briefly outlined above. Extensive documentation on the R code may be found here . This algorithm is also available for python and MATLAB . The climatology period used for calculating the MHWs is, and will reamain, 1982-01-01 to 2011-12-31.
The default map layer, 'MHW Category', shows the categories of the MHW occurring at each pixel on the chosen day. One may also choose 'MCS Category', which shows the same, but for cold events. Annual summaries and daily anomaly values also exist in the MHW Tracker database, but this functionality has not yet been reintroduced to v2.0 of the Tracker.
The Marine Heatwave Tracker was developed by Robert Schlegel and is an outcome of the Marine Heatwaves International Working Group . Therefore, this work has been directly and indirectly supported by several governmental, academic, and private organisations/funding bodies. The full list with links to further information is provided below in alphabetical order:
DAL - Dalhousie University
OFI - Ocean Frontier Insitute
UTAS - University of Tasmania
This app was developed for the Firefox web browser. Therefore the first fix for any observed bugs is to re-open the Marine Heatwave Tracker in Firefox.
The Tracker is visually heavy and may appear clumsy on smaller screens (e.g. cell phones). The app has been optimised for use on mobile devices as much as is possible.
Occasionally the marine heatwave polygons in the time series plots do not render correctly. Changing the date selection range will allow the figure to re-render correctly.
Very rarely when the app starts up no MHW pixels will be displayed. Refreshing the website will fix this.
The map panel may not show up on some computeres running on the Windows operating systems. This is usually remedied by accessing the Tracker in Internet Explorer / Microsoft Edge.
If the MHW pixels appear, but the map remains grey, this is usually due to internet speed. Refreshing often allows the map tiles to render correctly.
To report any bugs or to provide any other feedback on the app please contact the developer at: firstname.lastname@example.org
To cite the app itself please use:
Schlegel, R. W. (2020). Marine Heatwave Tracker. http://www.marineheatwaves.org/tracker. doi: 10.5281/zenodo.3787872
Yes. The source code for the MHW Tracker is freely available in a GitHub repo and is protected under the terms of the MIT License . For questions about the use or adaptation of the source code please contact the developer at: email@example.com
A press release was issued for the Marine Heatwave Tracker on May 27th, 2019. A link to the initial release on the Ocean Frontier Institute (OFI) page may be found here .
Any use of the NOAA OISST data should be accompanied by the following two reference:
Reynolds, R. W., Smith, T. M., Liu, C., Chelton, D. B., Casey, K. S., and Schlax, M. G. (2007). Daily high-resolution-blended analyses for sea surface temperature. J. Clim. 20, 5473–5496. doi: 10.1175/2007JCLI1824.1
Banzon, V., Smith, T. M., Steele, M., Huang, B., & Zhang, H. M. (2020). Improved Estimation of Proxy Sea Surface Temperature in the Arctic. Journal of Atmospheric and Oceanic Technology, 37(2), 341-349. doi: 10.1175/JTECH-D-19-0177.1
The marine heatwave data displayed in this app were calculated in R with the package heatwaveR. To cite heatwaveR in publications please use:
Schlegel, R. W., and Smit, A. J. (2018). heatwaveR: a central algorithm for the detection of heatwaves and cold-spells. J. Open Sour. Softw. 3:821. doi: 10.21105/joss.00821
The definition and categorisation of marine heatwaves may be found in the following two papers:
Hobday, A. J., Alexander, L. V., Perkins, S. E., Smale, D. A., Straub, S. C., Oliver, E. C. J., et al. (2016). A hierarchical approach to defining marine heatwaves. Progr. Oceanogr. 141, 227–238. doi: 10.1016/j.pocean.2015.12.014
Hobday, A. J., Oliver, E. C. J., Gupta, A. S., Benthuysen, J. A., Burrows, M. T., Donat, M. G., et al. (2018). Categorizing and naming marine heatwaves. Oceanography 31, 162–173. doi: 10.5670/oceanog.2018.5205