Remove unused params in oxygen module for iswO2

[wathen]

Description of Work

Fixes #51

Testing Instructions

1. Check right optional parameters have been removed

[wathen]

@jimc101 from the description in the issue you say that "legacy ERSEM" and "Weiss 1970" are the only options to choice from though it looks like the options are "legacy ERSEM" and "Wanninkhof 2014" from the code

ersem/src/oxygen.F90

Lines 101 to 109 in 7acae16

	if (legacy_ersem_compatibility) then
	! Old formulation for the Schmidt number,
	! left for documentation and back compatibility
	sc = max(0.0_rk, 1953.4_rk - 128._rk*ETW + 3.9918_rk*ETW**2 - 0.050091_rk*ETW**3)
	else
	! New formulation for the Schmidt number for O2 following Wanninkhof 2014
	T = max(min(ETW,40.0_rk), -2.0_rk)
	sc = 1920.4_rk - 135.6_rk*T + 5.2122_rk*T**2._rk - 0.10939_rk*T**3 + 0.00093777_rk*T**4._rk
	endif

[jimc101]

Sorry, this isn't right. The option relates to the code here and the way the saturation concentration is calculated.

This option should be reduced to legacy (or old) ERSEM and Weiss 1970. I would put Weiss first, since this is the option most users are likely to select. Also, there is no guard for invalid values. So something like:

if weiss:
    ...
elif old_ersem:
    ...
else
    throw exception
fi

could work. These would need to be matched up in the call to get_parameter. What do you think?

[wathen]

Ahh I see, is get_parameter a FABM thing?

[wathen]

@jimc101 having a safe guide for an incorrect parameter would be good in most places in the code though that would be done in a separate issue

[jimc101]

Sorry - I recommend you switch to just deleting the invalid options in the text string and not reordering the loop. This can be addressed in a separate issue (under optimisations). As you say, all valid options should also be tested, but again this can be addressed through a separate issue.

[jimc101]

Okay - looks good.