Monday, October 16, 2017

On The More Robust Sea Level Computation Techniques - 6

Fig. 1 SA 0-200 m
In this series I have provided some views on how best to calculate and compute thermal expansion and contraction with the in situ measurements available in the World Ocean Database (WOD).

One important event in that process is the use of the TEOS-10 toolkit provided by the scientific community (On The More Robust Sea Level Computation Techniques, 2, 3, 4, 5).

The importance of TEOS-10 should not be underestimated:
Fig. 2 SA 201-400 m
"On climatic time scales, melting ice caps and regional deviations of the hydrological cycle result in changes of seawater salinity, which in turn may modify the global circulation of the oceans and their ability to store heat and to buffer anthropogenically produced carbon dioxide." (Abstract, Metrologia 53 (2016), R1)

Fig. 3 SA 401-600 m
"Melting polar glaciers raise the sea level and influence the surface salinity distribution, and in turn may affect the large scale vertical and horizontal circulations in the oceans which continuously store, release or displace huge amounts of heat and dissolved gases." (ibid, R2)

"It is evident from climatology and geosciences that atmospheric
Fig. 4 SA 601-800 m
relative humidity, ocean salinity and seawater pH are key parameters for observing, modelling and analysing the increasing effects of global warming on ecosystems and society. However, despite their widespread use and relevance, the metrological underpinning of these parameters is inadequate, relies on century old provisional concepts, lacks
Fig. 5 SA 801-1000 m
traceability to the SI, or suffers from ambiguities and deficiencies of definitions, conventions and measurement techniques. The recent introduction of the international standard TEOS-10, the Thermodynamic Equation of Seawater 2010 (IOC et al 2010), has raised new awareness of these long standing and increasingly urgent problems, and has at the same time offered new perspectives for overcoming them.
" (ibid)
(IOP Science, PDF, emphasis added). The PDF is well worth downloading (no cost) and is filled with helpful reasoning as to why coherence is in the cards since the introduction of TEOS-10.

Fig. 6 SA 1001-3000 m
I have provided some source code as an example for using TEOS-10 (The Art of Making Thermal Expansion Graphs).

Thermal expansion and contraction is claimed to have been the major factor in sea level change for a century or so, and is claimed to have been more of a factor way back when than it is now (On Thermal Expansion & Thermal Contraction, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25).

Fig. 7 SA >3000 m
That assertion does not pass the smell test when, at the same time, it is also asserted that global warming has been increasing, with most of the increasing heat (~93%) ending up in the oceans.

The TEOS-10 and other formulas show that thermal expansion has decreased over the past ~50 years, even as more heat has been going into the ocean (On Thermal Expansion & Thermal Contraction - 25).

Fig. 8 SA All depths
Based on the in situ ocean temperature and salinity measurements processed by TEOS, ice sheet melt in Greenland and Antarctica has been going on in greater amounts and for a longer time than previously thought (Antarctica 2.0, 2).

Today's graphs focus on Absolute Salinity, an advanced concept for not only studying ocean water thermodynamics, but also for clarity and consistency (see  IOP Science link above).

Like temperature, Absolute Salinity (SA) varies with depth, and does so in a non-intuitive manner from time to time.

In these graphs (Fig. 1 thru Fig. 7) I used the usual Dredd Blog depth levels to show each level compared to the mean average of all the depths.

In the graph at Fig. 8 I placed all depths, along with the mean average again, on one graph.

It shows a relatively stable Absolute Salinity, the largest departure from the pack being the shallowest level (Fig. 1).

That probably reflects ongoing surface water freshening due to ice sheet and glacial melt acceleration.

Remember what the experts wrote in the quotes above: "Melting polar glaciers raise the sea level and influence the surface salinity distribution, and in turn may affect the large scale vertical and horizontal circulations in the oceans" (see IOP Science link above).

The next post in this series is here, the previous post in this series is here.

No comments:

Post a Comment