Guest essay by Eric Worrall
A new research paper claims that the Antarctic Ocean is staying cold, because it receives large infusions of “old water”, water which has been sitting in the freezing cold ocean depths since before the start of the machine age.
Antarctic Ocean Climate Change Mystery Could Be Explained By Deep, Old Water
A new study suggests that the Antarctic Ocean has remained unaffected by climate change and global warming due to deep, old water that is continually pulled to the surface.
A new University of Washington study reveals why the Antarctic Ocean might be one of the last places to experience the effects of global warming and human-driven climate change.
Over the years, the water surrounding Antarctica has stayed roughly the same temperature even as the rest of the planet continues to warm, a fact often pointed out by climate change deniers.
Now, a new study uses observations and climate models to suggest that the reason for this inconsistency is due to the unique currents around Antarctica that continually pull deep, old water up to the surface. This ancient water hasn’t touched the Earth’s surface since before the machine age, meaning it has been hidden from human-driven climate change.
“With rising carbon dioxide you would expect more warming at both poles, but we only see it at one of the poles, so something else must be going on,” said Kyle Armour of the University of Washington and lead author of the study. “We show that it’s for really simple reasons, and ocean currents are the hero here.”
The abstract of the study;
Southern Ocean warming delayed by circumpolar upwelling and equatorward transport
The Southern Ocean has shown little warming over recent decades, in stark contrast to the rapid warming observed in the Arctic. Along the northern flank of the Antarctic Circumpolar Current, however, the upper ocean has warmed substantially. Here we present analyses of oceanographic observations and general circulation model simulations showing that these patterns—of delayed warming south of the Antarctic Circumpolar Current and enhanced warming to the north—are fundamentally shaped by the Southern Ocean’s meridional overturning circulation: wind-driven upwelling of unmodified water from depth damps warming around Antarctica; greenhouse gas-induced surface heat uptake is largely balanced by anomalous northward heat transport associated with the equatorward flow of surface waters; and heat is preferentially stored where surface waters are subducted to the north. Further, these processes are primarily due to passive advection of the anomalous warming signal by climatological ocean currents; changes in ocean circulation are secondary. These findings suggest the Southern Ocean responds to greenhouse gas forcing on the centennial, or longer, timescale over which the deep ocean waters that are upwelled to the surface are warmed themselves. It is against this background of gradual warming that multidecadal Southern Ocean temperature trends must be understood.
The world’s oceans contain enough cold water to quench any imaginable anthropogenic global warming for hundreds, more likely thousands of years. If that deep water is upwelling around Antarctica, keeping the Southern Ocean cold, it is difficult to see how significant global warming can occur, or significant Antarctic contribution to sea level rise can occur, until that reservoir of freezing cold deep ocean water is finally depleted.