function [K_1]=bulkmod(S,T,P,k)
% % W J Schulz 22 Dec 2009
% SO 513 Lab 1
% 
% Purpose: Computes the secant bulk modulus for sea water per
% Pond and Pickard's "Introductory Dynamical Oceanography", 2nd Ed.
%
% Variables:
%   k = array of coefficients for the secant bulk modulus computation
%   K = secant bulk modulus
%   input:
%    S= salinity in practical salinity units
%    T = Temperature in degrees Celsius
%    P = pressure in bars (where 1000 bars ~ 100 meter depth)


%calculate the secant bulk modulus
K_1 = k(1) + k(2).*T + k(3).*T.^2 ...
    +k(4).*T.^3 + k(5).*T.^4 ...
    +k(6).*P + k(7).*T.*P ...
    +k(8).*T.^2.*P + k(9).*T.^3.*P ...
    +k(10).*P.^2 + k(11).*T.*P.^2 ...
    +k(12).*T.^2.*P.^2 ...
    +k(13).*S+k(14).*T.*S ...
    +k(15).*T.^2.*S+k(16).*T.^3.*S ...
    +k(17).*S.^(3/2)+k(18).*T.*S.^(3/2) ...
    +k(19).*T.^2.*S.^(3/2)+k(20).*P.*S ...
    +k(21).*T.*P.*S+k(22).*T.^2.*P.*S ...
    +k(23).*P.*S.^(3/2)+k(24).*P.^2.*S ...
    +k(25).*T.*P.^2.*S+k(26).*T.^2.*P.^2.*S;
    
%end function