by Jim Steele
There are two stories that claim to explain most of the observed ocean warming. One story holds that recent ocean warming is caused entirely by human emissions, amplifying the greenhouse effect. That story is supported by correlations with rising CO2 levels across the globe. The second story holds that the El Niño-Southern Oscillation (ENSO) and solar heating have conspired to warm the oceans. This second story is supported by data illustrated in NOAA’s (A) graph of ocean heat flow, with more heat entering the eastern tropical Pacific and Atlantic (yellow) than is released. That high heat flux region is regulated by ENSO and the Pacific Decadal Oscillation (Graph E). The white regions show no net heat flux into the quarter of the ocean surface. Such observations do not support the first account of uniform warming from a thickening CO2 layer.
Wherever there is more heat flowing into the ocean than venting out, the ocean will warm. All scientists agree that Any absorbed heat can only be vented away through the cool surface of the ocean. only about 2-10 microns thick.
Coincidentally, greenhouse infrared heat only penetrates a few microns into the skin’s surface. Therefore, any warming of the skin’s surface can be quickly radiated back into space. Any warming of the skin’s surface increases evaporation, further cooling the ocean. Ultimately, 99% of the time, the skin’s surface is warmer than the air immediately above it, and therefore warms the air. Those three drivers make ocean warming due to greenhouse gases relatively insignificant.. Conversely, because solar heat penetrates the surface below where it cannot radiate away, Solar energy is better at warming the oceans.
The ocean can store heat for longer periods of time than anywhere else where saltwater is overlaid with fresh water. This creates what is called a subsurface barrier layer that prevents the normal upward convection of hot water to the skin for ventilation. Because The salt barrier is denser and does not rise when the temperature below the surface is limited.
The natural Hadley circulation causes an increase in moist air around the equator and a decrease in dry air in latitudes north and south of the equator. This causes high evaporation rates but reduced rainfall at those latitudes (yellow areas in graphic B) make the sea water relatively saltierr. As the Trade Winds are pulled toward the equator, they also bend westward, pushing saltier ocean water and atmospheric water vapor toward the equator and westward. Where the northerly and southerly trade winds converge, the Intertropical Convergence Zone forms (the blue equatorial region) creating the most concentrated water vapor and rainfall. Freshwater precipitation covers saltier groundwater forming tropical barrier layers that retain heat then redistributed globally (Figure C).
The tropics recorded cooler temperatures than predicted by solar heating, while temperatures outside the tropics were warmer than predicted (Graphic D) Although the tropics receive the greatest amount of solar heat, they still have a “surplus” of heat that does not increase air temperature when stored in subsurface layers. Ocean currents carry that excess heat toward the poles into cooler waters. There, hot groundwater easily rises to the surface and vents any stored heat (the blue areas in graph A). That venting allows air temperatures outside the tropics to warm more than expected.
However, for story 2 to best explain the observed ocean warming trend, there must be an increase in solar heat absorption in the eastern Pacific and eastern Atlantic. Believers in the CO2 story dismiss such an increase in solar heat by pointing to a decrease in solar radiation from the Sun. However, The observed reduction in cloud cover increases solar heating. A La Nina event and a La Nina-like (negative) Pacific Decadal Oscillation lasting 20 to 30 years (Graph E) produce a cooler eastern Pacific Ocean that reduces cloud cover and increases solar flux into the ocean.
Furthermore, The increased east-west temperature difference during La Nina-like conditions amplifies the strength of the Trade Winds. Stronger winds increase the transport of warm surface and groundwater into the western Pacific, where water can be stored at depths of 200 m (Graphic F) until vented by an El Niño event, as well as supplying heat to the Indian Ocean (Sprintall 2014) or into poleward ocean currents. The increased transport of warm water increases global temperatures. This is why Jones (2022) calls these drivers the Pacific Heat Engine.
During El Nino and Decadal Oscillation events, the eastern Pacific Ocean is cloudier and the Trade Winds are weaker, resulting in cooler oceans. El Nino-like conditions prevail during the Little Ice Age.The shift to more La Niña-like conditions since 1850 has increased heat flux and heat redistribution, contributing to modern warming. The La Nina-like heat redistribution also explains why NOAA does not observe an increase in heat content in the eastern Pacific (gray area of Graph G) but does observe an increase in heat content in the western Pacific.
Finally, scientists integrating the transport of heat and salt from all the ocean currents built an ocean conveyor belt that carries warm water from the Pacific, through the Indonesian island straits into the Indian Ocean, around southern Africa into the Atlantic, and north into the Arctic (Graphic H). The ocean conveyor belt explains why the Atlantic is warmer and saltier. The conveyor belt also explains why Arctic sea ice is declining. Where warm Atlantic water first flows into the Arctic accounts for most of the sea ice loss observed within the Arctic Circle. A thick layer of warm Atlantic water exists at depths of 100 to 900 meters (Graphic I). It slowly vents its heat through the insulating sea ice, but the open water vents 35 times more than the greenhouse warming, making Arctic temperatures three times warmer than the global average.
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