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Sunday, November 9, 2014

New excuse for the "pause" of global warming #58: Colder eastern Pacific and reduced heat loss in other oceans

 


Temperature and salinity

Temperature

The oceans tend to be stratified, the principal factor being temperature; the bottom waters of the deep parts are intensely cold, with temperatures only slightly above freezing.
The surface zone, where temperature variations are perceptible, is between 330 and 1,000 feet (100 and 300 metres) thick. It is more compressed in the temperate eastern Pacific, along the coasts of North and Central America, where cold water appears at a shallower depth compared with the central and western Pacific.
Ocean temperatures in the North Pacific tend to be higher than those in the South Pacific because the ratio of land to sea areas is larger in the Northern Hemisphere and because Antarctica also influences water temperature.
The mean position of the thermal equator (the line on the Earth on which the highest average air temperatures are found; the line migrates latitudinally with the changing angular distance from the Equator of the Sun) in the Pacific, although it lies in the Northern Hemisphere, is nearer to the geographic equator than in the Atlantic and Indian oceans.
There is a pronounced difference in temperature and salinity between the surface and deep zones of the Pacific. ... (200 of 8,333 words)
http://www.britannica.com/EBchecked/topic/437703/Pacific-Ocean/36090/Temperature-and-salinity






paper published today in Geophysical Research Letters finds excuse #58 for the 18-26 year "pause" or hiatus" of global warming: Colder eastern Pacific (30% contribution) and reduced heat loss in other oceans (70% contribution). So increased heat loss in the Pacific, and decreased heat loss in the Southern and subtropical Indian Oceans & subpolar North Atlantic allegedly "explain" the "pause." Natural ocean oscillations could explain this, but not a steady rise of greenhouse gases.

According to the authors, however,
"A different mechanism is important at longer timescales (1960s-present) over which the [natural] Southern Annular Mode trended upwards. In this period, increased ocean heat uptake has largely arisen from reduced heat loss associated with reduced winds over the Agulhas Return Current and southward displacement of Southern Ocean westerlies."

Surface warming hiatus caused by increased heat uptake across multiple ocean basins

S. S. Drijfhout


The first decade of the twenty-first century was characterised by a hiatus in global surface warming. Using ocean model hindcasts and reanalyses we show that heat uptake between the 1990s and 2000s increased by 0.7 ± 0.3Wm−2. Approximately 30% of the increase is associated with coldersea surface temperatures in the eastern Pacific. Other basins contribute via reduced heat loss to the atmosphere, in particular the Southern and subtropical Indian Oceans (30%), and the subpolar North Atlantic (40%). A different mechanism is important at longer timescales (1960s-present) over which theSouthern Annular Mode trended upwards. In this period, increased ocean heat uptake has largely arisen from reduced heat loss associated with reduced winds over the Agulhas Return Current and southward displacement of Southern Ocean westerlies.
http://hockeyschtick.blogspot.com/2014/11/new-excuse-for-pause-of-global-warming.html

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