Tidal albedo's, what is the cumulative effect on GW ?

Question

What % is it of the total albedo?

Answer 1

There are about 356000 km of coastline worldwide [1] and I estimate a typical tidal zone at 50 m.  This gives 17800 km^2 of tidal zones in a total area of 5.1 E8 km^2 [2]. A paper by Kim et al [3] gives a seasonal fluctuation of albedo on Korean tidal flats from .13 to .15 in spring and summer, respectively.  Part of the change in albedo is due to changes in the angle of incidence of sunlight, so the numbers given are an upper limit.  A fuller analysis would use the Fresnel equation for reflectivity and the Mie equation for scattering together with empirical measurements of the BRDF [4].  The Korean numbers may not be indicative of the earth as a whole, but may suffice for an order of magnitude calculation.  If the earth warms, the tidal flats may have a higher summer albedo increasing the average albedo of the earth to a maximum of 7 E-5%.  Multiply by the average solar isolation of 341 W/m^2 to get a maximum negative feedback of about 2 E-4 W/m^2.