Spatiotemporal variability of dissolved inorganic macronutrients along
the northern Antarctic Peninsula
Abstract
The northern Antarctic Peninsula (NAP) is a key region of the Southern
Ocean due to its complex ocean dynamics, distinct water mass sources,
and the climate-driven changes taking place in the region. Despite the
importance of macronutrients in fuelling primary production and driving
the strong carbon uptake and storage, little is known about their
spatiotemporal variability along the NAP. Hence, we explored a 24-year
time series in this region, primarily sampled by the Brazilian High
Latitude Group, to understand the processes involved in the spatial and
interannual variability of macronutrients. We found high macronutrients
concentrations, even in surface waters and under strong phytoplankton
blooms. Minimum concentrations of dissolved inorganic nitrogen (16 μmol/
kg), phosphate (0.7 μmol/kg), and silicic acid (40 μmol/kg) along the
NAP are higher than those recorded in surrounding regions. The main
source of macronutrients is the intrusions of modified Circumpolar Deep
Water (mCDW), and this is enhanced by local sources, such as organic
matter remineralisation, water mass mixing, and mesoscale structures.
However, we identified a depletion in silicic acid due to influence of
Dense Shelf Water (DSW) from the Weddell Sea. Macronutrient
concentrations shows substantial interannual variability driven by the
balance between the intrusions of mCDW and advection of DSW, which is
largely modulated by the Southern Annular Mode and to some extent by El
Niño-Southern Oscillation. These findings are critical to improving our
understanding of the natural variability of this Southern Ocean
ecosystem and how it is responding to climate changes. Associate Editor