Abstract
AbstractProjections of climate impacts on marine net primary production (NPP) are reliant on Earth System Models (ESMs) that do not contain dynamic ice sheets. We assess the impact of potential Greenland ice sheet meltwater on projections of 21st century NPP using idealized ESM simulations. Under an extreme melt scenario, corresponding to 21st century sea level rise close to 2 m, Greenland meltwater amplified the decline in global NPP from a decrease of 3.2 PgC/yr to a decrease of 4.5 PgC/yr, relative to present. This additional reduction in NPP predominately occurs in the North Atlantic subtropical and subpolar gyres, as well as Atlantic eastern boundary upwelling systems. Accelerated NPP declines are the result of both surface freshening and reductions in upwelling‐favorable winds enhancing phytoplankton nutrient limitation. Our findings indicate that including a dynamic Greenland ice sheet in ESMs could have large impacts on projections of future ocean circulation and biogeochemistry.
Highlights
Net primary production (NPP) in the oceans is the base of the marine food web and the primary source of energy to higher trophic levels (Chassot et al, 2010; Pauly & Christensen, 1995)
Under the most extreme Greenland ice sheet melt scenario (GrIS200), projected global net primary production (NPP) declines increase by 1.3 PgC/yr over the 21st century, relative to RCP8.5
The overwhelming majority of these additional NPP reductions is confined to the Atlantic basin, with declines enhanced by 0.8 PgC/yr in the North Atlantic and 0.5 PgC/yr in the South Atlantic
Summary
Net primary production (NPP) in the oceans is the base of the marine food web and the primary source of energy to higher trophic levels (Chassot et al, 2010; Pauly & Christensen, 1995). 21st century global NPP is projected to decline by up to 20% (Bopp et al, 2013) with declines exacerbated on multicentennial timescales (Moore et al, 2018) Such global declines are typically driven by surface ocean warming in low and midlatitudes increasingly stratifying the upper ocean and reducing nutrient concentrations in the euphotic zone of nutrient‐limited waters (Bopp et al, 2013; Laufkötter et al, 2015; Steinacher et al, 2010). These declines are generally somewhat offset by shoaling of the mixed layer depth and sea ice loss reducing light limitation in high latitudes (Bopp et al, 2013; Steinacher et al, 2010)
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