Hello, dear friend, you can consult us at any time if you have any questions, add WeChat: daixieit

ENVS335: Global Carbon Cycle

Week 4 workshop: Introduction to CO2Sys

Feburary 2023

What is CO2Sys: Performing carbon chemistry calculations by hand is time consuming and prone to human error. In 2007, two scientists developed a set of spreadsheets to calculate carbon chemistry in seawater. The spreadsheet was developed into a software called CO2Sys, which is available for a suite of platforms including Microsoft Excel, Matlab, Python etc. In this workshop, you will access and download the Microsoft Excel version and learn how to input data and perform calculations. You will need to use CO2Sys to complete assignment 1.

Step 1. Access and download CO2Sys for excel

a. Navigate to the following website:

https://cdiac.ess-dive.lbl.gov/ftp/oceans/co2sys/CO2SYS_calc_XLS_v2.3/

b. Download the file named CO2Sys_v2.3.xls and save to your local hard drive or elsewhere.

CO2 sys v2.3 is used to calculate carbon chemistry in seawater using a series of macros. If you want more information or get stuck, please visit the document on Canvas titled CO2SYS_Macro Instructions.pdf.

Step 2. Open CO2Sys v2.3

(a) Double click to open the excel file. You will be asked to disable or enable macros. You must ENABLE MACROS for the programme to work. If you do not enable macros, the calculations will not work. If you make a mistake and disable macros, simply close the file and reopen it again.

Step 3. Navigating CO2Sys v2.3

The excel file contains three worksheets:

1. INFO: provides details of the software development, version and values used in the software, including references.

2. INPUT: provides information on the source of constants used in the calculations

3. DATA: this is the most useful sheet as it allows the user to INPUT information and after a series of calculations, provides a comprehensive suite of results.

(a) Please check that you have the following settings selected:

1. INFO: you do not need to change anything on this worksheet

2. INPUT: ensure you have the following selected

Step 4. Inputting data into CO2Sys and calculating carbon chemistry.

(a) Navigate to the DATA worksheet. In columns labelled INPUT CONDITIONS (A to E),     you can insert data on up to 5 parameters:  Salinity, Temperature (。C), Pressure (or depth, assumed 0 if left blank). Note that total Si (silicate) and Total P (phosphate) are optional (assumed 0 if left blank)

(b) In OUTPUT CONDITIONS (F and G), you can insert new temperature parameters. For example, if ocean temperature increases from 5 to 8。C, the INPUT condition would be 5。C and the OUTPUT condition would be 8。C. The results would be reported in the RESULTS  (output conditions). However, you can change temperature and other properties in Input Conditions only (A to E).

(c) CO2Sys will only work if you input at least 2 out of the 4 carbon variables (H to L, fCO2 and pCO2 are the same). The carbon properties are as follows:

TA = total alkalinity

TCO2 = total inorganic carbon (equivalent to DIC)

pH = seawater pH

pCO2 or fCO2  = partial pressure of CO2  or fugacity of CO2

To clear data (yellow cell) and clear results (green cell), click in the relevant cell.

To run the macro, press the red START bar at the top of the spreadsheet. You will be asked if you have entered the data correctly. Say YES.

If you insert data into the INPUT CONDITIONS only, results will be reported in RESULTS (input conditions).

Now let’s check that you are using the spreadsheet correctly.

Check Test 1:

Insert the temperature, salinity, pH and pCO2  from Table 1 and task 2 into the INPUT and CONDITIONS columns on the DATA worksheet. Assume 0 total P and 0 total Si. The results for TA (total Alkalinity), TCO2  (or DIC), carbonate ion, and Revelle Buffer Factor are reported in Table 2.

If your answers are correct, move to check test 2.

If your answers are incorrect, please ask for help.

Table 1. Summary of parameters in the surface ocean (0m)

Table 2. Summary of results using data from Table 1.

Check Test 2: Compare the difference in the Revelle buffer factor, pH and Ωarg  in the low and high latitude ocean using properties in Table 3 when (a) pCO2  is 390 μatm and (b) when pCO2 increases to 420 μatm and (c) if pCO2  increases to 420 μatm and temperature increases by 5。C. Results are reported in Table 4.

Note: to change the temperature (part c), you can insert 25 and 8。C into the input column  and 30 and 13。C into the output column, then run the macro. You then need to look at the OUTPUT results for the effect of increased temperature.

Table 3. Summary of input parameters in the surface of the low and high latitude ocean

Table 4. Summary of results using information in Table 2.

If your answers are correct, you are ready to start the assignment

If your answers are incorrect, please ask for help.