Wind-induced modulation of seasonal phytoplankton blooms in the North Atlantic derived from satellite observations

Abstract

We examined the interannual variability in the timing and magnitude of seasonal phytoplankton blooms in the North Atlantic (70ЊN-10ЊN, 90ЊW-10ЊE) in relation to variability in wind forcing during the bloom period using satellite data from 1998 through 2004. When averaged over the period extending from 1998 to 2004, seasonal increases in phytoplankton in the subpolar North Atlantic were observed predominantly during the spring, while the increases occurred between autumn and winter in the subtropical region. The major modes of interannual variability in bloom timing and magnitude from empirical orthogonal function analysis exhibited large spatial coherency across the North Atlantic. These patterns of variability can be explained, in large part, by the pattern of interannual variability in bloom-period wind mixing. Although convection is important in the seasonal development of blooms, wind-induced mixing during the bloom period appeared to be the key forcing agent contributing to interannual variability in the intensity of blooms. Increased wind-induced mixing during the bloom period reduced bloom magnitude over the subpolar and northern subtropical regions while enhancing it over the southern subtropical region. Atmospheric variations associated with interannual variability in wind mixing during the bloom period also appeared to affect variability in the timing of bloom onset. The major mode of interannual variability in the timing of North Atlantic blooms indicates a possible link to the North Atlantic Oscillation.

Factors controlling interannual variability of vertical organic matter export and phytoplankton bloom dynamics – a numerical case-study for the NW Mediterranean Sea

“…By contrast, a relatively calm weather period following the onset of the 2005 spring bloom allows phytoplankton to grow undisturbed and reach higher concentrations than in 2008. In conclusion, we posit that wind-induced mixing during the bloom period is a key forcing agent contributing to interannual variability in both the intensity and timing of the blooms, in agreement with the satellite chlorophyll analysis performed by Ueyama and Monger (2005) for the North Atlantic.…”

“…Several authors have pointed out the importance of windinduced mixing during the bloom period as the key forcing process contributing to the interannual variability in both timing and intensity of the bloom (Ueyama and Monger, 2005;Waniek, 2003). Nevertheless, to which extent the bloom variability is connected to the variability of the vertical flux of organic matter remains under discussion.…”

“…Timing and intensity of the bloom show latitudinal and interannual variability mainly determined by the variability in atmospheric forcing (Henson et al, 2009;Ueyama and Monger, 2005;Waniek, 2003). Henson et al (2009) showed that the onset of the bloom in the North Atlantic, between 40 • N and 45 • N, can vary from year to year by as much as 20 weeks.…”

Seasonality of North Atlantic phytoplankton from space: impact of environmental forcing on a changing phenology (1998–2012)

“…Limitations and advantages of the methods employed to characterize seasonal changes in chl a concentration A variety of approaches have been proposed to characterize phytoplankton seasonality using remote sensing data (Ueyama & Monger, 2005;Rolinski et al, 2007;Platt & Sathyendranath, 2008;Thomalla et al, 2011;Zhai et al, 2011;Racault et al, 2012;Sapiano et al, (Table 1) was fitted to bloom statistics, although combinations resulting in problems of collinearity were excluded (e.g., those including wind stress and its components). The covariate explaining more deviance was determined by comparing the decline in deviance explained after deleting each covariate one at a time.…”

“…the spring phytoplankton bloom, and have highlighted the great variability in this event and a trend towards an early occurrence of these blooms in northern latitudes in recent years Platt & Sathyendranath, 2008;Henson et al, 2009;Kahru et al, 2011;Zhai et al, 2011), as well as the importance of trophic mismatches (Beaugrand et al, 2003;Platt et al, 2003;Koeller et al, 2009;Kristiansen et al, 2011). Secondary pulses during the fall in temperate latitudes and autumn/winter blooms in subtropical and tropical regions have received in general less attention (but see Ueyama & Monger, 2005;Martinez et al, 2011;Cole et al, 2012;Sapiano et al, 2012).…”