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SIR-B synthetic aperture radar ocean-wave spectra for a 200-km pass crossing the Agulhas current off the coast of Africa are analyzed. A significant enhancement of one spectral peak along the northern edge of the current is attributed both to amplification of the waves by refraction-dominated wave-current interaction and to transient specular backscatter contributions spatially correlated to the waves. 2 m s-• toward the southwest. The brightened area in columns 9 to 13 is thus presumably associated with a phenomenon along the north edge of the current. The three bright lines in column 17 are spurious.Finally, weather information, nearshore wave measurements, and current measurements in the Agulhas were gathered along with the SAR data. Surface weather charts (provided by the South African Weather Bureau) for 1200 UT on October 6 and 7, shown schematically in Figure 3, indicate passage of a cold front over the observation area a day before the pass. Across the front, the winds shifted from east-southeasterly at 10-15 kt (5.1-7.7 rn s-•) to faster southwesterly winds up to 25 kt (12.8 m s--•). Nearshore wave measurements were provided by the University of Cape Town, with the assistance of the South African National Research Institute of Oceanology. Most important was a pair of measurements from a waverider buoy (in 27 m of water) at East London at 1200 and 1800 UT on October 7. These indicated an 11.3-s swell period and a 6.5-s wind sea period; the significant wave height was 2.6 m. Information on the Agulhas itself showed the current to be in essentially a normal, undisturbed state. A current measurement along the north edge of the Agulhas, taken a week and a half before the SIR-B overflight indicated a current vector of 2.6 rn ß s-• directed approximatel• along the 200-m depth contour (a typical situation), though the high-speed core of the current was somewhat closer to shore than normal. A METEOSAT infrared image from October 6 (Figure 4) shows the current, a band of warm water originating in the tropics, to be approximately aligned with the coast. In particular, there is no evidence of a .major current meander. 15,389 15,390 IRVINE AND TILLEY: OCEAN WAVE SPECTRA AND WAVE-CURRENT INTERACTION

Seasat synthetic aperture radar ocean wave spectra for a 900‐km pass are analyzed and interpreted in the context of both their probable generation sources and their surface current and bathymetric modifiers. Systematic vector wavenumber variations of several times the standard error of determination (∼1.5 % in magnitude and 0.9° in direction) occur along the entire 900‐km pass. The large‐scale spatial variation of a 200‐m swell system can be accurately accounted for as a result of dispersion from a distant storm. The more local variations are qualitatively well correlated in position with known currents and bathymetry but show systematic biases that appear partly due to an environmentally dependent instrument transfer function in the regions of high current and highest sea state. There is also substantial evidence that a large angular deviation in the center of the pass is the result of a mesoscale eddy just to the east.

Investigations in the Shetland Isles in the summer of 1973 have produced many new algal records for the area, including several of particular interest for the British flora in general. Those discussed here are Bolbocoleon piliferum N.Pringsh., Blastophysa rhizopus Reinke, Ochlochaete ferox Huber, Asparagopsis armata Harv. (the Falkenbergia-phase occurs in Shetland) (by I. Tittley); Audouinella spetsbergensis (Kjellm.) Woelk., Kallymenia reniformis (Turn.) J. Ag. (with impacted cystocarps and carpospores developing in situ) (by M. Guiry); Cladophora pygmaea Reinke (new to the British Isles) and Endodictyon infestans Gran (suggested to be a plethysmothallus of Ectocarpus) (by G. Russell).The marine algal vegetation of the Shetland Isles is of particular interest because these islands mark tile northern limits of the British Isles, witll a climate which is markedly cooler and less sunny than even that of the neighbouring Orkneys. As might be expected the flora is a somewhat depauperate British one, many species which are at least locally common in the Orkneys being apparently completely absent from Shetland. Conversely, it is much richer than that of the Faeroes, but lacks some of the subarctic species which occur there, e.g. Halosaccion ramentaceum (L.) J.Ag., Ptilotapectinata (Gunn.) Kjellm. and Alariapylaii (Bury) LAg. (B~rgesen & J6nsson, 1905). A general description of the main marine vegetation units is given in Irvine (1974a) but the marine flora is still insufficiently known. However, an intensive study by a team of phycologists in July and August 1973, briefly reported elsewhere (Irvine, 1974b), has uncovered many interesting facets of the phenology of Shetland seaweeds, has shown that several species have a much more northerly range than was previously supposed, and has added a few new species to the known British flora. It was felt that these points were of sufficient general interest to merit rather fuller and more prominent treatment than could be given in a general flora or in quantitative vegetational studies. Accordingly, a series of notes are presented here by the individual phycologists mainly responsible for investigating the taxa concerned. ACKNOWLEDGEMENTS

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