|Fig. 1 Layers 5,12 @ WOD Database Map|
Perhaps we should review why we are incrementally moving our observation from the Equator toward the poles.
It is because, generally speaking, the temperatures will tend to emerge from similar environments, which is better for comparisons, because we are comparing temperatures at latitudes with equal distances from the Equator.
|Fig. 2 Layer Five|
Well, it is because "that is where the money is" as the bank robber said when asked why she robbed banks.
Why we research the deep water is indicated by a scientific paper in Nature:
"Observational datasets derived from the Argo float data and other sources indicate that the ocean heat content above about 700 m did not increase appreciably during the 2000s, a time when the rise in surface temperatures also stalled. Hiatus periods with little or no surface warming trend have occurred before in observations, and are seen as well in climate-model simulations. So where does the excess heat in the climate system go if not to(Deep-ocean Heat Uptake, 2011, emphasis added). The paper points out that the greatest heat sink is in the deep waters of the ocean (thus, the most likely place to look for any "missing" heat).
increase surface temperatures or appreciably increase upper-ocean heat content?
Fig. 3 Layer Twelve
Tracing changes in global deep-ocean heat content indicated by the model results would require better observed ocean heat-content analyses. In particular, observations of deep-ocean temperatures, which are not generally available now but are planned under Argo, also limit our ability to accurately calculate the sea-level rise contribution due to thermal expansion that depends on ocean heat-content changes.
Examination of ocean heat-content trends by basin ... indicates qualitatively similar results to the global ocean, with decreases in heat-content trends above 300 m and increases below 300 m for the hiatus periods compared with all other periods."
Since more and more deep ocean observations from ARGO and other sources have been making their way into the WOD database, we use it for our datasets.
Anyway, the paper quoted above bolsters the Dredd Blog hypothesis that the ocean temperatures deep enough to have temperatures below 4 degrees C are vast expanses where heat fluctuation will impact ocean volume, density, etc. (Water is the most important exception to the general rule, At 4 °C water expands on heating or cooling).
This is discussed at more length in another series (On Thermal Expansion & Thermal Contraction, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11).
In the two layers depicted at Fig. 1, together with their temperature variations graphed at Fig. 2 and Fig. 3, we see that something is changing the temperatures from time to time (and therefore there is both expansion and contraction).
The next post in this series is here, the previous post in this series is here.