Appendix C 



Introduction 



In April and May 1986 Interna- 

 tional Ice Patrol (IIP) conducted a 

 study east of the Grand Banks of 

 Newfoundland in which airtxjrne 

 radar imagery of the sea surface 

 was compared with surface-truth 

 data. Sea surface roughness was 

 mapped using a real aperture, X- 

 Band, Side Looking Airborne 

 Radar (Sl-AR) aboard an HC-130 

 aircraft; surface-truth measure- 

 ments consisted of hydrographic 

 measurements made from 

 USCGC EVERGREEN (WMEC 

 295) and the trajectories of 

 satellite-tracked drifting buoys. 



The primary goal of the experi- 

 ment was to determine how well 

 and how reliably the IIP SLAR 

 could detect water-mass boun- 

 dries. A knowledge of the location 

 of the major boundries in the IIP 

 operations area (40°-50°N, 39°- 

 57°W) is useful in predicting the 

 motion of icebergs, an important 

 part of MP's responsibility. 



The study focused on a warm core 

 eddy spawned from, and interact- 

 ing with the North Atlantic Current 

 (NAC). No attempt is made to 

 describe the dynamics of the eddy 

 because the data are insufficient 

 for such an effort. Indeed, neither 

 the renfXJtely-sensed data nor the 

 hydrographic data define the eddy 

 txjundries completely and unambi- 

 guously. Only from the drifting 

 buoy data is it clear that the 

 feature is an eddy. The treatment 

 of the oceanographic data is 

 undertaken solely to help under- 

 stand the SLAR imagery. 



Observations of an Oceanic Front 

 South of Flemish Pass 



Donald L. Murphy 



LT lain Anderson 



LTJG Neal B. Thayer 



57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° 



r2" J ;" mm I.I II ri tun iii| nil i 



38° 





GRAND BANKS 

 OF 

 NEWFOUNDLAND §.. 



TAILOF 

 THE 

 "--. BANK 



m ill mi l m il iiiiii i i i iiiiiiriiiiiiiiiiiiiiii i iiiiiii n iiiiriiiiiiiiiiiiiiiiiiiiii M iiir i ii i iiiii 



Figure C-1 Schematic of the major current systems near the 

 Grand Banks of Newfoundland. The study area is shown by 

 the shaded rectangie. 



Bacltground 



Circulation in the North Atlantic 

 Ocean east of the Grand Banks of 

 Newfoundland is dominated by 

 two major currents (Figure C-1): 

 the southward-flowing, cold and 

 relatively fresh (<2°C and <34.3 

 ppt) Labrador Current (LC) and 

 the northeastward-flowing warm 

 and more saline (>12°C and >35.5 

 ppt) NAC. The mean dynamic 

 height field is reasonably well 

 mapped, due in large part to the 

 efforts of IIP, which conducted 

 routine hydrographic surveys of 



the region from 1934 to 1978, 

 excepting the years of World War 

 II. From these data, maps of 

 monthly mean dynamic height 

 relative to the 1000 dbar level for 

 April through June were devel- 

 oped by Soule (1964) and later 

 updated by Scobie and Schultz 

 (1976). Figure C-2, the mean 

 dynamic topography for April, 

 shows the narrow LC following 

 along the eastern edge of the 

 Grand Banks from Flemish Pass 

 to the Tail of the Bank. The other 

 months, May and June, show no 



53 



