Multicentennial record of Labrador Sea primary productivity and sea-ice variability archived in coralline algal barium

Abstract

Accelerated warming and melting of Arctic sea-ice has been associated with significant increases in phytoplankton productivity in recent years. Here, utilizing a multiproxy approach, we reconstruct an annually resolved record of Labrador Sea productivity related to sea-ice variability in Labrador, Canada that extends well into the Little Ice Age (LIA; 1646 AD). Barium-to-calcium ratios (Ba/Ca) and carbon isotopes (δ13C) measured in long-lived coralline algae demonstrate significant correlations to both observational and proxy records of sea-ice variability, and show persistent patterns of co-variability broadly consistent with the timing and phasing of the Atlantic Multidecadal Oscillation (AMO). Results indicate reduced productivity in the Subarctic Northwest Atlantic associated with AMO cool phases during the LIA, followed by a step-wise increase from 1910 to present levels—unprecedented in the last 363 years. Increasing phytoplankton productivity is expected to fundamentally alter marine ecosystems as warming and freshening is projected to intensify over the coming century.

Biogeochemical Cycling of Dissolved Zinc in the Western Arctic (Arctic GEOTRACES GN01)

“…We posit that the homogeneity of the deep layer likely represents deep water renewal from nearly 500 years ago (Timmermans et al, 2003), dating back to the Little Ice Age (Paasche & Bakke, 2010). Lower productivity (Chan et al, 2017), as well as circulation changes driven by the greater ice coverage and lower temperature (Aagaard & Carmack, 1989), could have resulted in different community composition and thus different Zn:Si ratios compared to what we currently observe in the surface and shelves. In a basin marked by low productivity and advective water mass movement, differences in the nutrient stoichiometry in these deepest water layers is unsurprising.…”

Variability in the Northern North Atlantic and Arctic Oceans Across the Last Two Millennia: A Review

“…Multiple parameters can be analyzed from these archives, including the width of the growth bands and their isotopic and elemental composition. This can reveal information about water temperatures, water mass variability, and productivity (Table ; e.g., Butler et al, ; Halfar et al, ; Reynolds et al, ; Chan et al, ; Moore et al, ; Reynolds et al, ). Through layer counting and the application of dendrochronological cross‐dating techniques, these annual bands can facilitate the construction of absolutely dated chronologies (referred as sclerochronologies).…”

“…Multiple parameters can be analyzed from these archives, including the width of the growth bands and their isotopic and elemental composition. This can reveal information about water temperatures, water mass variability, and productivity (Table 1; e.g., Butler et al, 2010;Halfar et al, 2013;Reynolds et al, 2013;Chan et al, 2017;Moore et al, 2017;Reynolds et al, 2017). Through layer counting 10.1029/2018PA003508 Sea surface temperature Core Alkenones Organic compounds synthesized by haptophyte algae, which mostly bloom in spring/summer at high latitudes.…”

Impact of model resolution on the representation of the air–sea interaction associated with the North Water Polynya

“…This may be due to different polynya masks and/or temporal analysis periods. In this regard, it should be noted that marine paleoclimate evidence from the eastern Canadian Arctic suggests that these recent changes are a continuation of trends that began at the end of the Little Ice Age associated with a warming of the West Greenland and Labrador Currents (Chan et al ., ; Moore et al ., ).…”