THE OCEAN, AN INDICATOR OF CLIMATE CHANGE
Through its permanent exchanges with the atmosphere, the ocean plays a major role for world climate. When the planet gets warmer, the ocean stores most of the energy received. It is possible to quantify and follow the extent of global warming by measuring the quantity heat stored by the ocean.
Our planet mainly receives energy from solar radiation. While the Earth captures part of this energy, the remainder is reflected beyond the atmosphere. The rapid increase in greenhouse gas emissions into the atmosphere causes an accumulation of heat within the climate system. The ocean absorbs over 90% of excess heat accumulated in the climate system and gets warmer. It is a crucial regulation role but the quantity of heat accumulated now has consequences on sea level evolution, temperature increase or ice melts…
THERMAL ENERGY, EL NIÑO, AND CLIMATE CHANGE
On a seasonal level, thermal energy stored in the ocean greatly influences atmospheric conditions. For instance, studying the evolution of the thermal content enables a monitoring of the evolution of hurricane intensity, or the return of the El Niño phenomenon. Oceanographers know this phenomenon very well : it is an episode of emphasized warming of surface waters in the Pacific (down to 300 meters deep) close to the South American coasts which frequently takes place around Christmas – hence, the Spanish name “El Niño” which refers to the baby Jesus. When this phenomenon occurs, it affects wind regimes, sea water temperature, precipitations and distribution of marine resources throughout the entire global tropical belt. Trough its extent and the size of the area affected, scientists know that El Niño affects global climate. However, the role of climate change in the frequency and the extent of the phenomenon has yet to be discovered.
The quantity of energy stored in the ocean is estimated by analyzing the thermal content of oceans. The temperature of ocean surface water is measured with sensors attached to satellites. The data is inserted into models*, which quantifies the thermal content of oceans over the entire water column.
According to estimations, oceans store up to the equivalent of 10 times the quantity of energy consumed by mankind over the same period.
It is more reliable to monitor the evolution of this quantity of energy than to observe surface temperatures. The latter are particularly sensitive to local vertical redistribution mechanisms and are not necessarily representative of global warming.
In the future, it is crucial to have better knowledge and accurate monitoring of the quantity of heat captured by the ocean to improve scientific knowledge on changes in the climate system, climate predictions and to analyze the impact of climate change mitigation policies.
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