Sensitivity of Shelf Sea Marine Ecosystems to Temporal Resolution of Meteorological Forcing

Abstract

Phytoplankton phenology and the length of the growing season have implications that cascade through trophic levels and ultimately impact the global carbon flux to the seafloor. Coupled hydrodynamic‐ecosystem models must accurately predict timing and duration of phytoplankton blooms in order to predict the impact of environmental change on ecosystem dynamics. Meteorological conditions, such as solar irradiance, air temperature, and wind speed are known to strongly impact the timing of phytoplankton blooms. Here, we investigate the impact of degrading the temporal resolution of meteorological forcing (wind, surface pressure, air, and dew point temperatures) from 1–24 hr using a 1‐D coupled hydrodynamic‐ecosystem model at two contrasting shelf‐sea sites: one coastal intermediately stratified site (L4) and one offshore site with constant summer stratification (CCS). Higher temporal resolutions of meteorological forcing resulted in greater wind stress acting on the sea surface increasing water column turbulent kinetic energy. Consequently, the water column was stratified for a smaller proportion of the year, producing a delayed onset of the spring phytoplankton bloom by up to 6 days, often earlier cessation of the autumn bloom, and shortened growing season of up to 23 days. Despite opposing trends in gross primary production between sites, a weakened microbial loop occurred with higher meteorological resolution due to reduced dissolved organic carbon production by phytoplankton caused by differences in resource limitation: light at CCS and nitrate at L4. Caution should be taken when comparing model runs with differing meteorological forcing resolutions. Recalibration of hydrodynamic‐ecosystem models may be required if meteorological resolution is upgraded.

Towards a multi-platform assimilative system for North Sea biogeochemistry

“…The ERSEM response to the atmospheric forcing is known to be sensitive to the forcing temporal resolution, leading to shifts of up to one week in the timing of the phytoplankton bloom (Powley et al [2020]). Since the assimilation does not alter the atmospheric forc- ing, the model mixing scheme, or the phytoplankton response to light, assimilating physical data was found to have relatively modest impact on chlorophyll bias, as well as spatial and temporal BC RMSD (between 5-7%, Table 3).…”

Low complexity model to study scale dependence of phytoplankton dynamics in the tropical Pacific

“…A simple example is the impact of wind stress on the vertical mixing and primary productivity in the water column: the phenomena observable on weekly timescales, such as phytoplankton blooms (e.g. see the critical turbulence hypothesis in [90]), may be sensitive to such details, as to whether we capture wind stress with an hourly, or 3-hourly resolution [91].…”

Low complexity model to study scale dependence of phytoplankton dynamics in the tropical Pacific

“…A simple example is the impact of wind stress on the vertical mixing and primary productivity in the water column: the phenomena observable on weekly timescales, such as phytoplankton blooms (e.g. see the critical turbulence hypothesis in [78]), may be sensitive to such details, as to whether we capture wind stress with an hourly, or 3-hourly resolution [79].…”