Heat and Carbon in the Deep Ocean
In the next five years, we aim to take significant steps in the advancement of our knowledge concerning heat and carbon penetration into the deep ocean
An increase in carbon dioxide concentrations in the atmosphere has caused heat to be trapped within the earth system, rather than being radiated away from the planet. More than 90% of this ‘excess’ heat has entered the ocean, meaning that the temperature rise in the atmosphere has been considerably less than would have been expected if all the heat had remained there. Approximately 25% of the carbon dioxide released to the atmosphere by human activity is now in the oceans.
Another consequence of ocean absorbing carbon dioxide is that the oceans are steadily becoming less alkaline – pH has dropped by around 0.1 pH unit globally, with unknown biological consequences for organisms that build their shells out of calcium carbonate or chalk.
For heat and carbon to enter the ocean they need to cross the air-sea interface, the processes controlling this transfer are of considerable importance in controlling our climate. Simple diffusion is one such process, however this is slow. Enhanced mixing driven by strong winds is an important factor in increasing these air-sea fluxes. However, the fastest rates of penetration into the deep ocean are created when water is transferred from the upper ocean to the interior, in the Southern Ocean and North Atlantic - the ‘hotspots’ of ocean uptake. When this heat and carbon enriched water enters the deep ocean it can be redistributed by ocean currents and alter circulation patterns.
One of the central goals of the NOC is to quantify how fast heat and carbon are penetrating into the deep ocean, where it is occurring, what controls these processes and whether they will carry on at their current rate. We will use a wide range of tools to address this, including; sea surface observations from merchant vessels, deep temperature data from profiling bouys, satellites, computer models and shipboard measurements of very high absolute accuracy, against which other systems are referenced.
How this provides a benefit to society
The rate of climate change is intimately coupled to the rate at which CO2 builds up in our atmosphere, as well as the rate at which excess heat is absorbed by the ocean. If the current processes controlling these factors were to change the consequences would be rapid; for these reasons early warning systems - like those operated by the NOC - are a vital tool to allow appropriate precautions to be put in place to counter any adverse societal consequences.