Climate variability and silicofl agellate fl uxes in Alfonso Basin (southern Gulf of California)

Abstract

We conducted a study from January 2002 to February 2008 on silicofl agellate fl uxes in Alfonso Basin at the entrance to the Gulf of California. Thirteen taxa were identifi ed in sediment trap samples, with Octactis pulchra as the dominant species. Total fl ux climatology reached a maximum value of 5 × 10 6 skeletons m -2 day -1 in December and then sharply decreased to a minimum value in February (2.3 × 10 3 skeletons m -2 day -1) concurrently with the climatological sea surface temperature (SST) minimum. Subsequently, there was a positive trend with a second relative maximum of 1.6 × 10 6 skeletons m -2 day -1 in September coincident with a maximum in climatological SST. During this period, there was a similar increase to 1.4 × 10 6 skeletons m -2 day -1 in May. Factor analysis identifi ed three patterns of variation: " subtropical oceanic, " " subarctic, " and " equatorial El Niño. " Factors had reasonable correlations with the Pacifi c decadal oscillation (PDO), North Pacifi c Gyre oscillation (NPGO), and El Niño Modoki indices (r = 0.53, 0.67, and 0.63, respectively). The fi rst and second modes were apparently linked to decadal climatic conditions correlated to PDO and NPGO, as suggested by the silicofl agellate species Dictyocha messanensis forma messanensis and the assemblage of D. epiodon and Distephanus speculum , respectively; the third mode was related to the presence of warm equatorial-oceanic waters identifi ed by D. messanensis forma spinosa , which defi nes El Niño infl uence. These results demonstrate the importance of the region where there is a confl uence of the low-frequency, high-latitude PDO, NPGO, and high-frequency El Niño signals. © 2012 by Walter de Gruyter.