Why ocean depth is key for how warming will affect marine life

Oct 5, 2022

Marine temperatures will exceed safe thresholds more quickly in deeper waters. Image: Unsplash/Marek Okon

Dr Yeray Santana-Falcón

Postdoctoral research scientist, CNRM-Méteo

Dr Roland Séférian

Research scientist, CNRM-Méteo

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The Ocean Sites network comprises a global system of “long-term, deepwater reference stations measuring dozens of variables and monitoring the full depth of the ocean, from air-sea interactions down to 5,000 metres”. Image: Santana-Falcón

Vertical profiles (0-1000 metres) of Tmin (blue) and Tmax (red) thermal anomalies relative to temperature average over the observational period, for both observations (shading) and model (lines). Model profiles are represented with (bold lines) and without (thin lines) applying the observational mask in space and time. Dashed lines demarcate the different layers of the ocean.

The “vertical profiles” show ocean temperatures through the depth of the ocean. Image: Modified from Santana-Falcón & Séférian (2022)

Illustration of how changes in the lower and upper bounds of the thermal ranges in response to climate change may either expand, contract or shift toward cooling or warming the thermal range, possibly affecting marine ecosystems.

As the oceans warm, thermal range boundaries will change. Image: Santana-Falcón & Séférian (2022)

Schematic explaining how the evolution of Tmin and Tmax may result in the emergence of substantial changes in current thermal ranges.

When Tmin crosses current Tmax, the ecosystem is considered to be exposed to a completely new thermal environment. Image: Santana-Falcón & Séférian (2022)

Projected changes in thermal range (red and blue lines and shading) and percentage of novel environmental temperatures (purple lines) at the end-of-the-century across three emission scenarios. Coloured bars to the right of the charts indicate overall changes to the thermal range.

Most thermal ranges are expected to warm and expand or warm and shrink. Image: Modified from Santana-Falcón et Séférian (2022)

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