New Atlantic/Pacific climate links cause US and island calamity

By JW Dowey - 04 Aug 2014 9:9:0 GMT
New Atlantic/Pacific climate links cause US and island calamity

Raja Ampat sits in the western Pacific, in Indonesia. Less than a metre above sea level, it is debateable how long this island and whole nations will be able to survive above the waves. Parliaments are now meeting underwater, to stress how urgent this problem is ; Island image; Credit: © Shutterstock

Shayne McGregor and many colleagues from the Universities of Hawaii and New South Wales (Australia) have drawn attention to the climate perturbations in the tropical western Pacific Ocean and the associated strengthening of Pacific trade winds. For the past 20 years, they found that these climate trends have been affected by Atlantic surface warming. They publish in the current issue of Nature: Climate Change in - Recent Walker circulation strengthening and Pacific cooling amplified by Atlantic warming.

The atmospheric Walker circulation has intensified and cooled the sea surface of the eastern Pacific. We have this last fact to thank for a current pause in global warming. The cause of atmospheric change like this has been difficult to judge, but Hawaii's climate models reveal that the distant Atlantic sea-surface warming displaced the main atmospheric pressure centres that are responsible. Observational data confirm the connection. The Walker circulation intensified eastern Pacific cooling have been driven by enhanced Atlantic warming since the 1990s.

The ultimate result has been North American rainfall trends, currently suffering in California from the lack of a recent El Niño as well as in the long-lasting Texan drought. These terrible droughts are joined by dangerous sea-level rises in the west Pacific. Island nations have been threatened for years but this trend makes action much more urgent.

More information on how climate change is affected by carbon emissions is here, where we discuss permafrost loss in Climate Change and Permafrost Loss. Perhaps the major point in this paper is that such climate change in one region can have extensive impact elsewhere around the earth's surface The power of the wind strength was a clue that something bigger than decadal variability was affecting Pacific trade winds. The basin of the Atlantic Ocean has warmed so rapidly that there was no longer the same equilibria between the two great oceans' pressure. Without the Atlantic, it was expected that Pacific Trades would slow down for the next hundred years.

In Hawaii, Professor Axel Timmermann's explanation would best explain exactly how it all happened: "The rapid warming of the Atlantic Ocean created high pressure zones in the upper atmosphere over that basin and low pressure zones close to the surface of the ocean. The rising air parcels, over the Atlantic eventually sink over the eastern tropical Pacific, thus creating higher surface pressure there. The enormous pressure see-saw with high pressure in the Pacific and low pressure in the Atlantic gave the Pacific trade winds an extra kick, amplifying their strength. It's like giving a playground roundabout an extra push as it spins past."

The worst news is that no one can predict yet when the cooling of the Pacific will end. Not surprisingly, the big hope is, yes, that old El Niño will blast the two oceans back into synch!