An international team of scientists has discovered that a change in ocean circulation allowed a large amount of carbon to be stored in the depths of the Atlantic Ocean, which reduced atmospheric CO2 and pushed the Earth’s climate into the coldest and most glacial stage of the last ice age. The team, led by Dr. Jimin Yu from the Australian National University and including Dr. Gianluca Marino from the Centre for Marine Research at the University of Vigo (CIM-UVigo), analysed the geochemical composition of marine sediments and carbonate microfossils extracted from the ocean depths.
Ocean circulation controls global climate by absorbing, storing and redistributing carbon, oxygen, heat and freshwater over large spatial and temporal scales. In this study, published in Nature Geoscience, the research team showed that deep, carbon-rich waters from the Pacific Ocean entered the South Atlantic Ocean and extended northward to approximately 20°S, at a depth of three to four kilometers, during the last ice age, about 20,000 years ago.
This change in deep ocean circulation increased its capacity to store carbon and caused atmospheric CO2 to decrease to levels that were approximately 50% lower than today. CO2 is a powerful greenhouse gas, so this decrease pushed the Earth into the Last Glacial Maximum, the peak of the last ice age. The volume of ice on our planet was, at that time, 50 million cubic kilometers greater than today, and the global temperature was 6° C colder than in pre-industrial times.
This detailed picture of ocean circulation and deep ocean carbon content during the Last Glacial Maximum has been researched for a long time, as it is fundamental to deciphering the interactions between the ocean and the atmosphere during a period that is often used to test models used in future climate projections.
Gianluca Marino, investigador distinguido da Universidade de Vigo e investigador principal do Laboratorio de Paleoclimatología do CIM-UVigo, utiliza un amplo portafolio de ferramentas xeoquímicas, micropaleontolóxicas e sedimentolóxicas, así como estatísticas probabilísticas para determinar cuantitativamente o momento, a magnitude e as taxas do cambio climático e o pasado do océano. A súa investigación achega información relevante para as políticas de mitigación e adaptación no contexto do cambio climático antropoxénico.
