Physical controls and interannual variability of the Labrador Sea spring phytoplankton bloom in distinct regions

Abstract

We investigated the variability of the spring phytoplankton bloom in the Labrador Sea, dividing into distinct biogeographical zones, then analyzing the relationship between the bloom and physical forcings. The spring phytoplankton bloom in the north Labrador Sea varied in intensity by a factor of 4 and in timing of onset by 3 weeks over the 11-year record from SeaWiFS satellite ocean chlorophyll, 1998-2008. This north bloom (north of 60 • N and west of the Labrador shelves) is earliest and most intense, owing in part to the offshore-directed freshwater stratification from the West Greenland Current. On interannual timescales, significant correlations were found between the north bloom intensity and ocean processes, namely offshore advection, eddy activity and runoff from Greenland. In contrast, the central Labrador Sea is later and weaker, and only a correlation between the bloom timing and irradiance was found. As the subpolar gyre shifts in strength and shape, freshwater outflow from the Arctic and Greenland changes, we may expect further changes in the biological response as indicated by these relationships.

Greenland meltwater as a significant and potentially bioavailable source of iron to the ocean

“…Thus, the GrIS may be capable of providing a quantitatively significant portion of bioavailable Fe (and inorganic macronutrients) 19 in a buoyant plume to the surrounding North Atlantic, capable of stimulating primary productivity. This could explain recent results 29 showing a strong correlation between peak phytoplankton blooms off the coast of Greenland and GrIS runoff. Other factors such as buoyancy of the meltwater plume and further photochemical degradation and release of nanoparticulate Fe may allow the glacially derived Fe to remain within the euphotic zone of farther-afield marine waters.…”

Sei whale movements and behaviour in the North Atlantic inferred from satellite telemetry

“…Most of the 27 ARS bouts detected occurred when whales were well within the Labrador Sea and lasted from 2 up to 5.5 d. At least 4 individuals eventually moved to the waters just south of the Greenland shelf, where C. finmarchicus dominates the mesozooplankton biomass in spring and early summer (Head et al 2003, Frajka-Williams & Rhines 2010. In light of that evidence it is reasonable to assume that the tagged whales moved to the Labrador Sea because that region still plays an important role in their feeding ecology.…”

A Characterization of Greenland Ice Sheet Surface Melt and Runoff in Contemporary Reanalyses and a Regional Climate Model

“…Quantitative assessments of the present and future rate of discharge are significant for understanding changes in global sea level (e.g., Shepherd et al, 2012;Church et al, 2013), ocean circulation (Driesschaert et al, 2007), and ocean productivity (Frajka-Williams and Rhines, 2010). It is thought that in recent years changes in the rate of GrIS iceberg calving and meltwater runoff have been making roughly equal contributions to global sea level rise (Rignot et al, 2008;van den Broeke et al, 2009;Fürst et al, 2015), but that runoff is becoming the dominant process for mass loss Enderlin et al, 2014).…”