Robert I Ellison wrote: > The transport index is calculated as the difference in ocean potential > energy anomaly near the centers of the subpolar and subtropical > gyres. It gives an indication of the strength of the Gulf Steam and > North Atlantic Current. You don't bother reading anything do you?
Those currents are generally horizontal surface currents and, while their strength and path do influence the weather around the North Atlantic basin, they are not the same as the THC. The THC is the link between the surface and the deepest portions of the world's oceans. The THC is the cause of the cold temperatures and high salinities of the deep layers. The paper you reference focuses on the currents nearest the surface, the authors stating: "As will be seen in the discussion of the subtropical gyre below, PEA changes comprise components arising from density changes directly forced by surface buoyancy flux and mixing (diabatic effects), and those due to the main pycnocline moving (quasi-adiabatically) up and down. In the Labrador Sea, convection is typically of order 1000 m but can exceed 2000 m . A weak pycnocline separates the LSW from the denser Nordic seas overflow waters but contributes very little through vertical movement to PEA variability..." Please notice the reference to "denser Nordic Seas overflow waters". Those waters are formed by the THC process in the Arctic Mediterranean. Don't you understand anything I write? E. S. --------------------------------------- > On Sep 21, 1:05 am, Eric Swanson <[email protected]> wrote: > > Robert I Ellison wrote: > > > Fo you take me for an idiot? [cut] > > > > > Do you comprehends nothing at all and simply respond with platitudes? > > > Energy flowing at a nearly constant rate? Ocean heat storage changes > > > very slowly? Neither of these statements mean anything at all. Of > > > course ocean temperature change according to the energy imbalance of > > > the planet - a matter of conservation of energy - don't you understand > > > my differential equation? The oceans are heated strongly at the > > > surface by SW radiation (a 100 odd metre deep warm surface layer) and > > > this interacts at many places with frigid sursurface conditions - both > > > with falling and rising water. But oceans have a heat storage > > > capacity a 1000 times that of the atmosphere - it is mostly at the > > > surface but it changes all the time. > > > > Yes, the ocean's mixed layer is typically about 100 meters thick. > > And, how did all that cold water below actually get there? Well, it's > > formed by sinking of waters at high latitudes via the THC. The warmer > > waters can not sink, due to their lower salt content and higher > > temperatures, which result in a lower density. > > > > > > > BTW - the 'transport index (bottom panel) estimates the strength of > > > the baroclinic gyre circulation in the North Atlantic, or the strength > > > of the Gulf Stream and North Atlantic Current system. The units (Mtons > > > s-1) are within a few percent of the volumetric unit of transport > > > (Sverdrups = 106 m3s-1). It is calculated from the difference of the > > > potential energy anomalies (PEA) near Bermuda and in the Labrador > > > Basin (top two panels). > > > > > The evolution of the index from 1950 through 2000 shows a circulation > > > reducing through the low NAO period in the 1960s, then strengthening > > > during the period of persistently high NAO over the next 25 years, > > > reaching a peak in the mid-1990s. They found that the timing and > > > mechanisms associated with PEA changes in each gyre varied, and were > > > dependent on both locally and remotely-forced changes in the ocean > > > (see paper for details).' [cut] > > > I have provided this link previously as well - some of this is very > > > difficult science unlike my attempts at science communication. Do try > > > to pay attention. > > > > That index appears to describe the gyre circulation in the North > > Atlantic Sub Polar Gyre, which has a strong wind driven component. > > The Gulf Stream is a wind driven current, which feeds into the North > > Atlantic Gyre. However, the THC appears to be located in the Nordic > > and Labrador Seas, with some fraction also occurring in the Arctic > > Ocean. this is not the same geographical location as the NA Sub Polar > > Gyre. > > > > I think you are missing the importance of the THC as a process of > > longer time scales with results which appear to dominate the long term > > record. There are also short term fluctuations in the THC, such as > > that which may have resulted from the Great Salinity Anomaly, starting > > in the early 1970's. During the early 1980's, there is evidence that > > the THC sinking in the Greenland Sea ceased. I suggest that the > > cooler winter conditions around the North Atlantic of that period may > > have been the result. My perception (based on satellite evidence over > > the last few years), is that the THC may have again weakened in the > > Nordic Seas. The cause this time might be the known freshening of the > > Nordic Seas as the sea-ice yearly melt has strengthened, allowing more > > fresh water to enter the Greenland Sea thru the Fram Strait. That we > > did experience a bit colder weather last winter in the Eastern US may > > have been the result, but, sad to say, I can not point to any > > acceptable proof. > > > > E. S.- -- You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. 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