Measuring temperature from space - Resource Bundle

Measuring ocean temperature from space

Measuring ocean temperature from space

Taking the temperature of the oceans

Taking the temperature of the oceans Key learning points: Sea surface temperature was historically measured from ships, but these measurements are too few to describe the whole ocean. Now, sea surface temperature is measured by sensors on satellites. Some sensors measure temperature using the thermal infrared portion of the electromagnetic spectrum, other sensors use the microwave portion of the electromagnetic spectrum. Satellite measurements allow scientists to collect data over the entire globe regularly so we can see how the ocean changes in time. There are some limitations to collecting sea surface temperature by satellite, as they can only ‘see’ the very surface (skin) of the water, which is why other measurements from buoys and ships, as well as ocean models are also needed.

Why do we want to know the temperature of the sea?

Why do we want to know the temperature of the sea?

Weather prediction

Weather prediction : Sea temperature affects weather patterns. Warm water provides energy to storms like hurricanes and typhoons. Climate change : Sea temperature is a key indicator of climate change. As the ocean warms up, ice melts and the sea level rises. Observing sea temperature helps track these changes, for example to predict future weather. Carbon Cycle: The ocean absorbs a lot of carbon dioxide (CO 2 ) from the atmosphere. A warmer sea stores less CO 2 . Understanding sea temperature helps scientists predict how the ocean helps to regulate our climate. Marine life: Many animals, like fish and coral, require specific temperature ranges. Measuring sea temperature helps us understand where they can live. If the sea gets too warm or too cold, these creatures may be harmed. Leisure and safety : Is the sea warm enough to swim in?

Measuring the temperature of the sea

Measuring the temperature of the sea Historically, sea temperature was measured using thermometers from shorelines, and from ships and buoys .  In the 19th century, measurements were made by drawing a water sample up to the ship in a wooden or canvas bucket. These were replaced by specially-designed insulated buckets to keep the temperature of the sample stable. From the 1930s, measurements were made in ship engine rooms, using the water taken in for cooling and other purposes. Since the late 1970s, measurements have been made by moored and drifting buoys and sensors have been fitted to the hulls of ships. Because oceans are very large, it is impossible to make a global map of temperature with these thermometer readings alone! Today, global temperature maps are made from measurements taken by sensors on satellites in space.  

Anatomy of a Satellite

Anatomy of a Satellite Earth Observation Satellites are satellites that orbit Earth with sensors designed to collect imagery and measurements of planet’s physics, chemistry and biology. These satellites come in many shapes and sizes. But they have a few parts in common: Sensors are the instruments that collect data about Earth processes or atmosphere

What do sensors measure from space?

What do sensors measure from space? Sensors measure the amount of light being reflected or emitted from the Earth's surface in different parts of the Electromagnetic Spectrum . Sensors may detect visible light (the wavelengths we can see with our eyes), but they can also detect much longer radio waves, microwaves and infrared radiation. Measuring the energy reflected or emitted in these different wavelengths on the Electromagnetic Spectrum can reveal additional information about the earth. The wavelength of a wave is the distance between a point on one wave and the same point on the next wave Long wavelength Short wavelength

How does a satellite measure temperature?

How does a satellite measure temperature? When we measure ocean temperature from satellites, we see the temperature at the surface (or ‘ skin ’) of the ocean. This is called Sea surface temperature (SST) . Some sensors measure temperature using the thermal infrared portion of the spectrum. These have the advantage of having a higher resolution, but observations are obscured by clouds. Other sensors use the microwave portion of the electromagnetic spectrum. These measurements have a lower resolution but can see through clouds. Scientists can combine measurements from multiple sensors to get a complete picture of global SST.

Why are satellites useful tool for measuring sea temperature?

Why are satellites useful tool for measuring sea temperature? The oceans are very large and water is always moving – this makes them hard to study! In the past, sea temperatures in the oceans could only be measured by ships and buoys. These measurements capture a single point in space and time There were big gaps between measurements Ship-based measurements are time-consuming and expensive Satellites have improved our ability to measure SST by allowing frequent and global coverage.

Global SST patterns

Global SST patterns The ocean and atmosphere systems are driven by solar radiation from the sun. Sea surface temperature is higher near the equator is because the equator absorbs more solar radiation compared to the poles. Heat is redistributed around the globe by winds, surface currents and the deep flow of in the thermohaline circulation. Did you know water can be below 0ᵒC in the ocean without turning into ice? This is because the salt in seawater lowers its freezing point. February 2023 August 2023

The top map shows a map of major ocean currents. The bottom map shows the average sea surface temperature from 2014-2023.

The top map shows a map of major ocean currents. The bottom map shows the average sea surface temperature from 2014-2023. Would you say that the temperature is influenced by the ocean currents? Global SST patterns

Yes!

Yes! Western sides of the oceans the isotherms are shifted towards the poles, as the western boundary currents carry warm water from equatorial regions The Gulf Stream transports relatively warm water across the Atlantic. Eastern boundary currents carry water from high latitudes can cause temperatures on the eastern sides of oceans to be cooler than you might expect. Isotherm: A line drawn on a map or chart joining points with the same temperature.

Trends in sea surface temperature

Trends in sea surface temperature Using satellite observations, we can monitor how sea surface temperature has changed over time. The average sea surface temperature has increased by about 0.6°C over the last 40 years ( 1980 to 2023). To identify long-term trends in temperature we look at the temperature anomalies – how much a given date differs from the long-term average. While there is an increasing trend there is year-to-year variability . This is due to largescale climate patterns like the El Niño Southern Oscillation (ENSO). Annual mean sea surface temperature anomalies (°C) for 60°S–60°N, relative to the average for the 1991–2020 reference period. Data source: ERA5, ESA SST CCI Analysis v3, ERSSTv5 , HadSST.4.0.1.0, HadSST4.0.1.0 . Credit: C3S/ECMWF . These figures are from the Climate Change Service of Copernicus, the European Union's Earth Observation Programme . For interactive versions of these plots see: https://climate.copernicus.eu/climate-indicators/sea-surface-temperature

This plot shows several different datasets which provide sea surface temperature over time.

This plot shows several different datasets which provide sea surface temperature over time. You can see the ‘ESA’ dataset – this is the one derived from satellite observations – is only availible from the 1980s onwards. For longer timeseries, the available historical data is fed into climate models to help fill in gaps and improve the accuracy of historical sea surface temperature measurements. These models provide a longer-term view of how sea surface temperatures have changed over time. Why do you think the differences between the datasets are larger in the earlier parts of the record? There was less data The data were less accurate All datasets show SST has increased over the last 30 years. Annual mean sea surface temperature anomalies (°C) for 60°S–60°N, relative to the average for the 1991–2020 reference period. Data source: ERA5, ESA SST CCI Analysis v3, ERSSTv5 , HadSST.4.0.1.0, HadSST4.0.1.0 . Credit: C3S/ECMWF . For interactive versions of these plots see: https://climate.copernicus.eu/climate-indicators/sea-surface-temperature

What are anomalies and how do we use them?

What are anomalies and how do we use them? When we measure the temperature of the oceans, some days will be warmer and some days will be cooler. What we really want to know is how much the temperature changes over time . An anomaly shows how different something is from what is normal or expected. It helps us identify if temperatures are higher or lower than usual. Instead of focusing on exact temperatures (which change all the time and with the seasons), we compare each measurement to an average temperature for that time of year. It is calculated by finding the difference in the temperature relative to a ‘baseline’ or long-term average , so for example if you wanted to find the temperature anomaly for a particular day : Anomaly = actual value – long-term average For example, if the average temperature in your classroom in December is 20.5 ᵒC, but this year the average in December is 18.2 ᵒC, the temperature anomaly is -2.3 ᵒC – a negative anomaly, so colder than expected!

Regional differences

Regional differences Sea surface temperatures vary regionally. Temperatures have risen in many parts of the world, while some places have become cooler. The map shows the trend in sea surface temperature between 1993–2023. The fastest warming has been observed in parts of the Arctic Ocean, the Baltic Sea, the Black Sea and parts of the Pacific Ocean South of Greenland and Iceland and the tropical eastern Pacific have a cooling trend. These patterns may be linked to other climatic phenomenon – for example the cooling in the eastern tropical Pacific is related to La Niña conditions from late 2020 to early 2023  Trend in annual sea surface temperature anomalies (°C/decade) for the period 1993–2023. Data source: ESA SST CCI Analysis v3.0. Credit: ESACCI/EOCIS/UKMCAS and C3S/ECMWF.

External resources

External resources Interactive visualization of sea surface currents, temperature and more - https://data.scripps.earth/argoviz/ https://myoceanlearn.marine.copernicus.eu/ Dashboard showing active argo floats https://www.ocean-ops.org/board?t=argo Climate Pulse - interactive web application developed and maintained by the Copernicus Climate Change Service (C3S) provides daily charts and maps of global surface air temperature and sea surface temperature and anomalies https://pulse.climate.copernicus.eu/

Explore Sea Surface Temperature time series

Explore Sea Surface Temperature time series A time series is a collection of measurements taken in the same location at different times. It can show us how conditions (such as temperature, salinity, number of organisms) change over time. This kind of data is often used when studying the climate.   Time series may show: Seasonality – a pattern that repeats at regular intervals reflecting seasonal variations or recurring cycles. Trends – a long-term increase or decrease in the measurements Unusual events – unpredictable irregular fluctuations The ProBleu team have produced time series of sea surface temperature for the regions shown in this map. You can find the timeseries in the catalogue under ‘Spreadsheets’. Example SST timeseries of the North West Shelf Sea area. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme .

North West Shelf

North West Shelf What is the range of temperature in this region? Can you describe the seasonality?   SST timeseries of the North West Shelf Sea area. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme . You can find the data used to make this timeseries in the catalogue under ‘Spreadsheets’. Long-term monthly average SST of the North West Shelf Sea area for the period 2014-2023. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme .

Baltic

Baltic What is the range of temperature in this region? Can you describe the seasonality?   SST timeseries of the Baltic area. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme . You can find the data used to make this timeseries in the catalogue under ‘Spreadsheets’. Long-term monthly average SST of the Baltic area for the period 2014-2023. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme .

Iberia Biscay

Iberia Biscay What is the range of temperature in this region? Can you describe the seasonality?   SST timeseries of the Iberia Biscay area. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme . You can find the data used to make this timeseries in the catalogue under ‘Spreadsheets’. Long-term monthly average SST of the Iberia Biscay area for the period 2014-2023. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme .

Black Sea

Black Sea What is the range of temperature in this region? Can you describe the seasonality?   SST timeseries of the Black Sea area. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme . You can find the data used to make this timeseries in the catalogue under ‘Spreadsheets’. Long-term monthly average SST of the Black Sea for the period 2014-2023. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme .

Western Mediterranean

Western Mediterranean What is the range of temperature in this region? Can you describe the seasonality?   SST timeseries of the Western Mediterranean area. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme . You can find the data used to make this timeseries in the catalogue under ‘Spreadsheets’. Long-term monthly average SST of the Western Mediterranean for the period 2014-2023. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme .

Eastern Mediterranean

Eastern Mediterranean What is the range of temperature in this region? Can you describe the seasonality?   SST timeseries of the Eastern Mediterranean area. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme . You can find the data used to make this timeseries in the catalogue under ‘Spreadsheets’. Long-term monthly average SST of the Eastern Mediterranean for the period 2014-2023. The data is from the European Space Agency (ESA) Climate Change Initiative (CCI) Programme .

Baltic Sea sea surface temperature timeseries

Black Sea sea surface temperature timeseries

Eastern Mediterranean sea surface temperature timeseries

Iberia Biscay sea surface temperature timeseries

North West Shelf sea surface temperature timeseries

Western Mediterranean sea surface temperature timeseries

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