Global Warming Is ‘Fundamentally’ Changing The Structure of Oceans
Climate change has wrought major changes to ocean stability faster than previously thought, according to a study published recently, raising alarms over its role as a global thermostat and the marine life it supports. The research published in the journal Nature looked at 50 years of data and followed the way in which surface water “decouples” from the deeper ocean. Climate change has disrupted ocean mixing, a process that helps store away most of the world’s excess heat and a significant proportion of CO2.
Water on the surface is warmer – and therefore less dense – than the water below, a contrast that is intensified by climate change. Global warming is also causing massive amounts of fresh water to flush into the seas from melting ice sheets and glaciers, lowering the salinity of the upper layer and further reducing its density. This increasing contrast between the density of the ocean layers makes mixing harder, so oxygen, heat and carbon are all less able to penetrate to the deep seas.
“Similar to a layer of water on top of oil, the surface waters in contact with the atmosphere mix less efficiently with the underlying ocean,” said lead author Jean-Baptiste Sallee of Sorbonne University and France’s CNRS national scientific research center. He said while scientists were aware that this process was under way, “we here show that this change has occurred at a rate much quicker than previously thought: more than six times quicker.”