Gulf Stream Eddies — Circulation Features 

 April 1979 and April 1982 



CZCS pigment images for 21 April 1979 (42-1), and 24 April 1982 

 (42-2), show that both warm- and cold-core rings are defined in terms of 

 ocean color which is traceable to the gradients in measured phytoplankton 

 pigment (Gordon ei al.. 1983). The gradients of pigment observed in these 

 eddies is due to the fact that they are rotating, which influences the density 

 field within the eddy. Nutrient-rich water is vertically mixed along the 

 sloping isopycnals of the eddies. In the anticyclonic mode, the sea surface 

 level, due to geostrophy, domes-up around the axis of a warm-core ring; 

 while in a cyclonic mode, it is depressed around a cold-core ring. 

 Therefore, in an anticyclonic eddy (warm-core ring) lighter, nutrient-poor 

 water will accumulate at its center and heavier, nutrient-rich water will be 

 swept to its rim. This distribution of nutrient-rich and -poor water dictates 

 the pattern of phytoplankton distribution observed in the eddies. In the 

 case of the warm-core ring (42-2) the higher concentrations of 

 phytoplankton will be found at the outer rim of the eddy, whereas in the 

 cold-core ring (42-1). the reverse will be true, with the central region 

 containing most of the phytoplankton-rich water. The false-color CZCS 

 pigment image (43-1) of the warm-core ring example (42-2), illustrates 

 how dramatically these differences can be displayed by the color 

 presentation. 



In summary, the explanation for the observed distribution of 

 phytoplankton pigments in rings argues that geostrophic principles apply 

 to these rings. Associated with this is the idea that these are the forces of 

 enrichment, thus the rotary motion induces nutrient transport along 

 isopycnals and phytoplankton production occurs when these isopycnals 

 intersect the euphotic layers of the ring water masses. 



Reference 



Gordon. H. R , D K. Clark, J. W. Brown. O. B. Brown, R H Evans, and W. W. 

 Broenkow. 1983: Phytoplankton pigment concentrations in the Middle Atlantic Bight: 

 Comparison of ship determinations and CZCS estimates. Applied Opliis, 22. 20-36. 



42 



uPBIT 0,i430 ;1hPP79 li30716 TO 16091b GMT 

 GRID CEHTEP DhTh: 16081T GMT 33-96N 070.5111 



GhIM 1-4=2 THRESHOLD OFF TILT rtMGLE S-O 

 ;UII EL iJ7 hZ 160 POLL -0-1 PITCH -0.0 VhU -0.0 



algorithms; 01 00 00 00 00 02 01 00 00 00 



809 SCAM line; PROCESSED 101 ^ChII LIME; MISHMG 



CIP VEP CPT Nij DPS VEP SPEC. # FPhME # 

 ','801005 ZE40401- V820501 F732040 ZG040401h 



42-1. Nimbus-7, Orbit 2480, 21 April 1979, CZCS Pigment Imag 



ORBIT 17663 24mPR82 155806 TO 160006 GMT GAIN 1-4=1 THRESHOLD OFF TILT hNGLE 10.0 

 GRID CENTER DhTh: 155906 GMT i:8.26N 069.48N SUN EL 63 AZ 160 POLL 0-3 PITCH -0.0 YAN 0-3 



algorithms: 02 01 01 00 00 03 02 00 00 00 



970 SCAN LINES PROCESSED SCAN LINES MISSING 



CIP VER CRT NO DPS VER SPEC- # FRAME # 



ZE270661 V821015 F732040 ZG270661 



42-2. Nimbus-7. Orbit 17668, 24 April 1982, CZCS Pigment Image, 



I 



