Deterioration caused by each of the considered 

 methods over one day assuming: Wave 

 height = 6', Wave period = 10 sec, and Relative 

 Velocity = 25 cm/sec. 



where 0.274 converts m/yr to cm/day. As shown 

 by White, et al., 1980, this equation agrees well 

 with the other equations used to model vertical 

 convective melting. 



The equations used to model melting caused 

 by wind-forced convection are derived from the 

 R&D Center report No. CG-D-62-80 (Figure C-2). 

 There appears to be a change in the slope of 

 the linear approximation of the plotted curves 

 at a relative velocity of about 25 cm/sec. A plot 

 of the slope of the linear approximation rate for 

 melting versus the log-|Q of the waterline length 

 of an iceberg was made for relative speeds less 

 than 25 cm/sec and for the section greater than 

 25 cm/sec (Figure C-3). The resulting linear 

 regression for each set of points was deter- 

 mined as: 



Insolation melting is relatively unimportant 

 in the model. R&D Center report figure #22 

 (Figure C-1) is the basis for the equation: 



SUN = 2.0*WEATHER*(0.5*ZTIME)/100 (1*) 



where SUN is in meters/day, ZTIME is in units 

 of half days (hence the 0.5) and the factor of 100 

 converts centimeters to meters. WEATHER is 

 set to 1 for cloudy/foggy conditions and to 2 for 

 clear conditions. The weather in the IIP 

 operating area is generally not clear, therefore 

 weather will be assumed always to be 1 for the 

 model. The 2.0 is taken as the smallest melt 

 rate (in cm/day) that covers the time period of 

 the average IIP season (March - August) (Figure 

 C-1). 



Neshyba and Josberger (1979) estimate ver- 

 tical buoyant convective melting as (White, 

 et al., 1980): 



v m (m/yr) = 2.78*T + 0.47 * T< 



(2*) 



where T is the temperature difference between 

 SST and ice surface temperature. This equation 

 was derived from data on a wide variety of 

 iceberg shapes. The temperature of the ice sur- 

 face was chosen as -1 °C. This temperature is 

 above the equilibrium temperature of ice and 

 sea water at 30 parts per thousand salinity of 

 -1.63°C. An ice surface temperature of -1 °C will 

 be used throughout the model. The equation 

 used to model vertical buoyant convective 

 melting is: 



BUOY = 0.274*(2.78*T + 0.47*T 2 )*ZTIME*0.5/100 



- for the portion of the relative velocity < 

 25 cm/sec: 



0.934 - (0.202 * log-io (RLEN)); (4*) 



- for that part of relative velocity > 25 

 cm/sec: 



0.660 -(0.151 * log-io(RLEN)), (5*) 



where RLEN is the present waterline length of 

 the iceberg. The wind forced convective 

 melting factor (FC) is calculated from equa- 

 tions 4* and 5*: 



FC(cm/day/°C) = 



(0.934-(0.202*log 10 (RLEN))*RELSPD (6*) 



FC = (0.660-(0.151 *log 10 (RLEN))*(RELSPD-25) + 



(0.934-(0.202*log 10 (RLEN)*(25) 



(7*) 



where RELSPED is the relative speed of the 

 iceberg with respect to the historical 

 geostrophic current. Equation (6*) is used when 

 the relative velocity is less than 25 cm/sec and 

 equation (7*) is used when the relative velocity 

 is greater than 25 cm/sec. RELSPED is 

 calculated by determining the (N-S, E-W) com- 

 ponents of the distance traveled between two 

 analysis time periods, dividing by the time dif- 

 ference and then subtracting the historical 

 geostrophic current. The magnitude of the vec- 

 tor (RELSPED) is then determined. There is an 

 admitted error in this calculation because at 

 present neither the wind driven current nor iner- 

 tial effects are taken into account. Five cm/sec 

 is added to the relative velocity since this is the 

 average value of water velocity observed in 

 calm conditions (White, et al., 1980). FC is 



68 



