Articles | Volume 12, issue 11
Biogeosciences, 12, 3641–3653, 2015
Biogeosciences, 12, 3641–3653, 2015

Research article 11 Jun 2015

Research article | 11 Jun 2015

Synoptic-scale analysis of mechanisms driving surface chlorophyll dynamics in the North Atlantic

A. S. A. Ferreira1, H. Hátún2, F. Counillon3, M. R. Payne1, and A. W. Visser1 A. S. A. Ferreira et al.
  • 1Centre for Ocean Life, National Institute of Aquatic Resources, Technical University of Denmark, Copenhagen, Denmark
  • 2Environmental Department, Faroe Marine Research Institute, Nóatún 1, P.O. Box 3051, FO 110 Tórshavn, Faroe Islands
  • 3Nansen Environmental and Remote Sensing Center, Thormóhlensgate 47, Bergen, Norway

Abstract. Several hypotheses have been proposed for the onset of the spring phytoplankton bloom in the North Atlantic. Our main objective is to examine which bottom-up processes can best predict the annual increase in surface phytoplankton concentration in the North Atlantic by applying novel phenology algorithms to ocean colour data. We construct indicator fields and time series which, in various combinations, provide models consistent with the principle dynamics previously proposed. Using a multimodel inference approach, we investigate the evidence supporting these models and how it varies in space. We show that, in terms of bottom-up processes alone, there is a dominant physical mechanism, namely mixed-layer shoaling, that best predicts the interannual variation in the initial increase in surface chlorophyll across large sectors of the North Atlantic. We further show that different regions are governed by different physical phenomena and that wind-driven mixing is a common component, with either heat flux or light as triggers. We believe these findings to be relevant to the ongoing discussion on North Atlantic bloom onset.

Short summary
Our main objective was to assess which bottom-up processes can best predict changes in phytoplankton surface spring blooms in the North Atlantic. We applied new phenology algorithms to satellite-derived data and compared four different metrics based on physical drivers of phytoplankton. We show that there is a dominant physical mechanism - mixed layer shoaling - and that different regions are governed by different physical phenomena.
Final-revised paper