Sentinel-3B image of the blooms

World Ocean Day: Observing our oceans from space in 2022-2023

8 June 2022-8 June 2023

Sentinel-3B image of the blooms
Sentinel-3B image of the blooms

Every year on 8 June, the world celebrates its oceans through World Ocean Day. Satellites continuously monitor the oceans, providing data to protect people and planet.

Last Updated

29 June 2023

Published on

08 June 2023

The oceans play a crucial role in how our planet functions, and have many impacts on our day-to-day lives. Satellites offer a way to monitor the oceans every day, with data contributing to weather forecasting, safety at sea and on our coasts, managing impacts of water quality on human health, and understanding the role our oceans play in climate change.

World Ocean Day is an opportunity to reflect on what we learned about the oceans from space in the past year, through our case studies.

Ocean colour provides insights in to ocean biology

Phytoplankton affect the colour of the ocean, which is in turn observable by instruments onboard satellites. In 2022, beautiful blooms in the Black sea inspired a case study explaining how current and future satellite missions observe these variations in colour, and how their data can be turned into 'true colour' images to visualise phytoplankton dynamics.

Sentinel-3B image of the blooms
Figure 1: Phytoplankton bloom seen through enhanced True Colour RGB, from Sentinel-3 OLCI instrument, 6 July 2022

Satellites monitor ocean heat content and its impacts

The past year provided yet more examples of how extreme heat is affecting our planet. The oceans are no exception, with a serious marine heatwave occurring in the Mediterranean Sea. This case study — Marine heatwave intensification threatens coral reef health — reflected on these phenomena, and how satellite can be used to observe events as they happen, and at climatic scales. This cases study formed part of an ongoing contribution to the United Nations Ocean Decade, and provides an interactive Jupyter Notebook to recreate the images in the case study.

 Sea surface temperature anomaly in the Mediterranean over the first 20 days of August 2022
Figure 2: Sea surface temperature anomaly in the Mediterranean over the first 20 days of August 2022 as measured by the AVHRR instrument on-board EUMETSAT's Metop-B satellite. These anomalies are calculated by subtracting the climatological mean of August over the period 1985-2007 from the mean over the first 20 days of August 2022.  The data used to calculate the climatological mean were taken from the ESA SST CCI and C3S reprocessed sea surface temperatures based on the OSTIA analyses (1981-present) distributed by the Copernicus Marine and Environmental Monitoring Service (CMEMS)

The Ocean observations from space confirm disruption of Earth's energy balance case study, summarised how satellite altimetry and gravimetry data contributes to estimates of ocean heat content, confirming a disruption of the Earth's energy balance as a result of increased heat absorption.

ime-series of Global Ocean Heat Content Change (GOHC) expressed as departure from 2002
Figure 3: Time-series of Global Ocean Heat Content Change (GOHC) expressed as departure from 2002. The red shaded areas around the red line represent the estimation uncertainties. The dashed red line represents the trend in Global Ocean Heat Content Change.  Grey shaded areas correspond to gaps in the data record caused by missing or erroneous data. The data were taken from space geodetic Ocean Heat Content and Earth Energy Imbalance data record (2002-2020) produced by Magellium/LEGOS distributed by AVISO+ with support from CNES

Oceans and carbon

As well as heat, the oceans also absorb carbon. Ocean colour, thanks to it's ability to observe both photosynthetic and calcifying phytoplankton species, can be used towards the quantification of ocean carbon pools. The case study Quantifying particulate organic & inorganic carbon in the ocean, another contribution to the UN Ocean Decade, shows how particulate organic and inorganic carbon can be estimated from satellite ocean colour data.

Comparing chlorophyll and POC concentrations

Particulate organic carbon concentration compare1
Figure 4: Sentinel-3A OLCI OC4ME chlorophyll concentration in the Barents and Norwegian Seas, 31 May 2022 11:00 UTC (left). Particulate organic carbon concentration derived from the same scene (right).

Extreme weather and the role of the ocean

The oceans are intimately connected to the weather. Ocean heat content fuels tropical cyclones, which can have devastating impacts on coastal communities. Another UN Ocean Decade case study — Tracking tropical cyclone impacts using altimetry — showed how data from multiple altimetry satellites provided information on storm surges, waves, and winds associated with several tropical cyclones in 2022.

Figure 5a: Evolution of Typhoon Hinnamnor, in terms of significant wave height
Figure 5b: Evolution of Typhoon Nanmadol, in terms of significant wave height
Figure 5c: Evolution of Typhoon Ian, in terms of significant wave height
Figure 5d: Evolution of Typhoon Fiona, in terms of significant wave height