LANOT Projects

Sargassum monitoring

PROJECT ENDORSED BY THE OCEAN DECADE (2021-2030). Initiative coordinated by the Intergovernmental Oceanographic Commission, UNESCO.

ASSOCIATED INSTITUTIONS

  • National Earth Observation Laboratory, Institute of Geography, UNAM.
  • Institute of Marine Sciences and Limnology, UNAM.
  • Institute of Atmospheric Sciences and Climate Change, UNAM.
  • Oceanus International.

Managers

Collaborators

  • Ing. Uriel de Jesús Mendoza Castillo
  • M. en C. Gabriela Gómez Rodríguez
  • M. en C. Francisco Javier Osorno Covarrubias
  • M. en Geog. Víctor Manuel Jiménez Escudero
  • M. en C. Alejandro Aguilar Sierra
  • Dr. Raúl Aguirre Gómez
  • Dr. Steven Czitrom
  • M. en C. Iván Penié Rodríguez
  • M. en C. José Antonio Quintero Pérez
  • Geog. Itzel Millán Ortega
  • Geog. Guadalupe Tapia Varela
  • M. en Geog. Ilma Maclovia Huy Domínguez

Fellows

  • Pas. Ing. Jesús Hernández Torres

Background

Half Moon Bay, Akumal.

Sargassum is a pelagic algae originating in the Sargasso Sea in the Atlantic Ocean; it normally floats in the ocean, being an ecosystem in itself that provides refuge to crustaceans, turtles and small fish, among other animals. The two main species of sargassum that reach the Mexican coasts are Sargassum natans and Sargassum fluitans; although they sometimes wash up on the beach, mixed with seagrass.
Since 2011, a massive arrival of this algae began, causing serious environmental and economic problems in the Mexican Caribbean.
At the National Earth Observation Laboratory, an algorithm based on satellite images was developed to monitor its annual arrivals, thus contributing UNAM to the solution of a national problem.

Objective

Carry out sargassum monitoring in the Mexican Caribbean region, offering resources such as vector files of its position at sea and RGB composites for better analysis.

Summary

An algorithm was developed to detect sargassum in the maritime zone near the coasts of Quintana Roo, extending towards Belize, Guatemala and part of Honduras; covering an approximate area of 150 thousand km2. Images from the Sentinel-2 satellites of the COPERNICUS Constellation of the European Space Agency are used. A mosaic is generated from 18 satellite images, this occurs every 5 days. To identify sargassum, atmospheric correction of images is carried out, among other processes, masks of clouds, land and beaches are applied, and bands 8, 8A, B4 and B11 are used to detect it. Processed Sentinel-2 tiles.

https://dataspace.copernicus.eu/explore-data/data-collections/sentinel-data/sentinel-2

To cover the five-day gap between the availability of Sentinel 2 images and thus provide an estimate of the movement of centroids identified in the sargassum detection process, ocean current data provided by HYCOM (HYbrid Coordinate Ocean Model) are used.

Https://hycom.org

From these data, a model was developed that predicts sargassum movement, considering only the surface current. Additionally, the wind vector component is added through the GFS (Global Forecast System) model.

https://www.ncei.noaa.gov/products/weather-climate-models/global-forecast

This information is being validated with field work using drift buoys that are attached to sargassum rafts and that during their journey collect and store velocity and position data. They are ultimately recovered on the beach.

In addition to sargassum dynamics, an animation was also generated that quantifies the number of sargassum strandings on the beach that occur during the mentioned 5-day period. To display and analyze the information, a web viewer was developed that integrates different information layers and allows quantifying the sargassum surface present in the study area. Queries can also be made to analyze time series with the same Sentinel 2 images, available in our databases. There is an image archive since late 2015, when this input became operational. On the other hand, other algorithms based on satellite sensors such as MODIS, VIIRS and ABI are under development; they will cover the time gap between the passes of the two Sentinel2 satellites, covering wider areas, reaching South America and much of the Atlantic.

It is important to mention that this algorithm is not capable of detecting sargassum under clouds, nor under their respective shadows; therefore, in the presence of cloudiness, the amount of sargassum is underestimated.

Sargassum detected on 2022-05-16 in the Mexican Caribbean region.

Documents

Sargassum Monitoring

Viewer

The viewer displays on a web map the sargassum polygons obtained from Sentinel-2 images. It allows analyzing both the latest results and those generated since late 2015.

It contains several tools, including: sargassum area calculation in a user-selected region, statistics of the last 10 processed mosaics and the attribute table of all detected sargassum polygons.

Sargassum Monitoring

Images

Latest views

True color RGB composites together with sargassum polygons from the monitoring region in the Mexican Caribbean. The total sargassum area recorded in square kilometers is shown.

These views are updated every 5 days, depending on the pass of the Sentinel-2A or Sentinel-2B satellites.