There have been some recent reports about research on ocean temperatures and how corrections are being made to the overall world temperatures as new information comes from better records. We have fairly good records of the land but, apart from the last ten years, there have only been temperature records of the seas surface and then only along regular shipping routes and at some ports. This has left the vast majority unrecorded.
Since 2004 we have had the Argo programme where 3500 floats have been placed in the oceans around the world and these are recording temperature and salinity from the surface down to 700 metres. For deeper levels there are no comprehensive records due to the extreme pressure and with total darkness there are no sources of energy to power monitoring equipment. It is easier to monitor the surface of Mars than the deep areas of our oceans. This proves to be the case as we have three surface rovers on Mars and none on the bottom of the deep oceans.
There has been a recent scientific report that the deep oceans have not warmed, but with no long term records how it was measured? Much of it was done with calculations of thermal expansion taken from satellite measurements of sea level. If the temperature of the upper levels of the oceans are known from the Argo float records, then calculations can be made of the expansion or contraction of that region of the sea and therefore a calculation can be made of the deeper parts. A bit tenuous? Well yes, but if you don’t have a thermometer down there you have to use a proxy method. The new Argo Deep program will add to the knowledge but that will not be deployed for some years yet...
A typical problem here is that water from the Gulf Stream sinks off the coast of Norway and reappears some 15 to 1000 years later in the Southern Ocean. What happened to it? Did its CO2 laden content and warmer temperature do any damage? We have no idea but I doubt if it will be good news.
The big action with climate change is in the deep oceans but the harsh facts are that we know very little about them
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