(Very powerful Kelvin Wave still moving eastward even as it begins to sink in off the coast of South America. Image source: NOAA.)
Likelihood for a significant El Nino later this year continued to increase as the most powerful Kelvin Wave on record continued its progress into the Eastern Equatorial Pacific. According NOAA’s recent April 13 assessment, the massive slug of anomalously hot Pacific subsurface waters continued to surge eastward, to deepen the 20 C isotherm and to spread out on or just below the surface.
NOAA’s most recent CPC report finds, in a bald refutation to assertions by climate change deniers, that:
A significant downwelling oceanic Kelvin wave that was initiated in January greatly increased the oceanic heat content to the largest March value in the historical record back to 1979 and produced large positive subsurface temperature anomalies across the central and eastern Pacific.
Extraordinary temperature departures in the range of 4-6 C above average stretched from a zone from 180 West Longitude to 80 West Longitude and ranged in depth from 30 to 70 meters. This very large zone of above average heat shattered global records even as it slid into position to begin re-delivering that excess to the atmosphere.
Perhaps more importantly, the nose of this wave of far warmer than normal water had begun to sag, pushing the 20 C isotherm deeper into the Eastern Pacific even as cooler water from the depths began to punch into the tail of the record hot Kelvin Wave, raising the 20 C isotherm in the Western Pacific. This downwelling force of a monster Kelvin wave appears to just now be initiating the start to a global weather-altering El Nino.
Hot Water Downwelling, Weakening Trade Winds
In the East, from 12 February to 13 April, the 20 C isotherm had plunged from about 25 meters below to around 100 meters of depth. During the same period, the isotherm from about 150 East Longitude to 170 West had risen from about 210 meters to 170 meters. At the subsurface, a continued rising of the isotherm in the West and its continued fall in the East would complete the transfer of warm waters across the Pacific and open the flood gates to the start of what could be an extraordinarily strong El Nino event as what is now a record Pacific Ocean heat content starts bleeding back to the atmosphere.
(20 C isotherm continues to rise in the Western Pacific [left side of graph] even as it rises in the East [right side]. Image source: NOAA.)
On the surface, trade wind weakening and reversals continued with a significant, though milder than those seen in January and February, backflow emerging in early April east of the Solomon Islands and coinciding with rather weak trade winds across the Equatorial Pacific. Such conditions continued to provide surface impetus to transfer warm waters across the Pacific even as record subsurface heat continued its transition eastward.
Chances for El Nino Rise
Accordingly, predictive forecasts both by NOAA and Australia’s Bureau of Meteorology are showing increasing potentials that El Nino will emerge. NOAA’s forecast now indicates that the chance for El Nino has jumped to over 50% by this summer and to 66% by the end of the year. Australia’s forecast is now showing a greater than 70% chance of El Nino over the same period.
In addition, El Nino type influences are already beginning to appear in world weather systems. A recent report by Dr. Simon Wang found that precursor El Nino conditions combined with effects related to climate change such as Arctic sea ice loss to spur and enhance epic drought conditions in California. Southeast Asia is already experiencing heat and dryness that is typically associated with a developing El Nino. Northern Brazil is also seeing increasing levels of heat and drought. To the North, Siberia is experiencing an extraordinary April onset to fire season while the northeastern US is somewhat cooler than average due to the persistent and anomalous strength of a dipole of warm temperature extremes in western North America and cool temperature extremes in eastern North America.
Many of these impacts, though expected in a normal El Nino year appear to be enhanced by effects related to human caused climate change such as sea ice loss and an amplification of the hydrological cycle increasing the frequency of extreme rainfall, drought and fire events (as in the California drought and the southeast Asian and Siberian fires).
(El Nino model runs by NOAA’s Climate Prediction Center show 66% potential for El Nino Development by November, December and January of 2014-2015. Image source: CPC/IRI.)
During a typical strong El Nino year, global weather disruptions can cause severe damage resulting in reductions to world GDP by as much as 5%. But with the added and enhanced severe weather effects due to climate change interacting with El Nino, overall impacts could be far more destructive. In addition, a release of what is currently record Pacific Ocean heat content into the atmosphere will likely set off new high temperature extremes, further pushing the global climate system toward the very dangerous 2 C warming threshold.