Ideas and perspectives: climate-relevant marine biologically driven mechanisms in Earth system models

Abstract

Abstract. The current generation of marine biogeochemical modules in Earth system models (ESMs) considers mainly the effect of marine biota on the carbon cycle. We propose to also implement other biologically driven mechanisms in ESMs so that more climate-relevant feedbacks are captured. We classify these mechanisms in three categories according to their functional role in the Earth system: (1) "biogeochemical pumps", which affect the carbon cycling; (2) "biological gas and particle shuttles", which affect the atmospheric composition; and (3) "biogeophysical mechanisms", which affect the thermal, optical, and mechanical properties of the ocean. To resolve mechanisms from all three classes, we find it sufficient to include five functional groups: bulk phyto-and zooplankton, calcifiers, and coastal gas and surface mat producers. We strongly suggest to account for a larger mechanism diversity in ESMs in the future to improve the quality of climate projections.

Light absorption by marine cyanobacteria affects tropical climate mean state and variability

“…The observed strong effect of cyanobacteria on the local vertical thermal structure of the water column is supported by one-dimensional and regional model studies of the Baltic Sea and the North Atlantic Ocean (Hense, 2007;Sonntag and Hense, 2011;Sonntag, 2013). In these studies, positively buoyant cyanobacteria lead to a local heating effect of up to 2 K and a mixed layer depth (MLD) shoaling of up to 20 m. These changes in the physical environment regionally promote growth of cyanobacteria, constituting a positive feedback loop between ocean biology and physics.…”

“…2). For bulk phytoplankton, the C : Chl ratio is set to R Phy = 60 mg C (mg Chl) −1 as is used in HAMOCC (Ilyina et al, 2013). This value lies in the middle of the observed range, which spans values from about 12 to 1286 H. Paulsen et al: Cyanobacteria light absorption more than 200 mg C (mg Chl) −1 , depending on species, light conditions, nutrient limitation, and temperature (e.g., Taylor et al, 1997).…”

“…We use MPI-ESM1.2, which consists of the coupled general circulation models for the atmosphere ECHAM (Stevens et al, 2013) and the ocean MPIOM (Jungclaus et al, 2013), the ocean biogeochemistry model HAMOCC (Ilyina et al, 2013) extended by prognostic N 2 -fixing cyanobacteria (Paulsen et al, 2017), and the land surface and terrestrial biosphere model including dynamic vegetation JSBACH (Reick et al, 2013;Schneck et al, 2013). The explicit model versions are ECHAM6.3.02p2, MPIOM1.6.2p2, HAMOCC5.2, JSBACH3.10, which are further developments of the models described in the references above.…”

An interactive ocean surface albedo scheme (OSAv1.0): formulation and evaluation in ARPEGE-Climat (V6.1) and LMDZ (V5A)

“…Indeed, changes in whitecaps and ocean color, whether due to climate variability or climate change, can modify the OSA, with potential impacts on photochemistry in the atmosphere and biological activity in the upper-most layer of the ocean (Hense et al, 2017).…”

Preface: Ernst Maier-Reimer and his way of modelling the ocean

“…Further papers address the topics of climate dynamics and impacts (Gaye et al, 2018;Heinze et al, 2018;Schwinger et al, 2017;Segschneider et al, 2018) as well as a critical appraisal of geoengineering (Lauvset et al, 2017). The collection is rounded off with a paper on model complexity (Kriest, 2017) and an outlook paper (Hense et al, 2017).…”