Characteristics of alkenone distributions in suspended and sinking particles in the northwestern North Pacific

We investigated alkenones recorded in suspended particles and a settling particle time series collected at three stations, 40N (40 degrees N, 165 degrees E), KNOT (44 degrees N, 155 degrees E), and 50N (50 degrees N, 165 degrees E), in the northwestern North Pacific from December 1997 to May 1999. Emiliallia huxleyi, the most abundant alkenone producer in this area, is present in surface to subsurface (to similar to 50 in depth) waters. The alkenone concentrations recorded in the Suspended particles indicated that the seasonal alkenone particle distribution differed significantly inter-annually. Alkenone export fluxes at the three sediment-trap stations ranged from 0.16 to 49.3 mu g m(-2) day(-1), and the maximum export flux. which occurred in summer to fall (July-November), was associated with a high organic carbon export flux. The amount of alkenone produced during the maximum export season accounted for 60-80% of the total annual amount of alkenone, and the alkenones accumulated in the sediment below the traps had characteristics corresponding to Subsurface waters during the summer-autumn season. Alkenone-derived temperatures recorded in suspended particles corresponded to the in situ temperature within similar to 2 degrees C. Although alkenone-derived temperatures corresponded approximately to the temperatures observed in the stratified subsurface waters at the three trap stations during the high-export season, large differences were observed during the low-export (winter-spring) period. For example, the alkenone-derived temperatures observed at stations KNOT and 50N were much higher than the in situ subsurface temperatures reported in the World Ocean Atlas 2001. Relatively large differences between alkenone-derived temperatures and in situ temperatures in the subarctic might be due to (1) a low-light limitation or (2) contributions of allochthonous alkenones in particulate material transported from subtropical areas within a warm-core ring. (c) 2006 Elsevier Inc. All rights reserved.