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Interactions between European shelves and the Atlantic simulated with a
coupled regional atmosphere-ocean-biogeochemistry model
Dmitry V. Sein, Joachim Segschneider, Uwe Mikolajewicz and Ernst Maier-Reimer
Max Planck Institute for Meteorology, Bundesstrasse 53, 20146 Hamburg, Germany; dimitry.sein@zmaw.de
1. Introduction
In the framework of NORDATLANTIK project the
numerical investigations of interactions of the water masses
on the European shelves with the Atlantic were carried out.
A regionally coupled model consists of the regional
atmosphere model REMO, the global ocean model MPI-OM
and the marine biogeochemical model HAMOCC, which
simulates biogeochemical tracers in the oceanic water
column and in the sediment (Mikolajewicz et al. 2005,
Maier-Reimer et al. 2005). The coupled domain includes
Europe, the North-East Atlantic and parts of the Arctic
Ocean (Fig.1).
The lateral atmospheric and the upper oceanic boundary
conditions outside the coupled domain were prescribed
using ERA40 reanalysis data. No momentum and heat flux
corrections was applied.
2. Model simulations
For better understanding of the influence of tidal dynamics
on long term ocean variability the model was run both with
(run A) and without (run B) tidal forcing, derived from the
full ephemeridic luni-solar tidal potential .
Figure 2. Tidal influence on SST. The difference
in mean SST (C) between run A and B
3. Biogeochemistry
The biogeochemical model HAMOCC5 has been spun-up
with anthropogenic CO2 concentrations starting in 1860
and using atmospheric forcing from the ERA40 reanalysis.
For years before 1958, the forcing was repeated in several
cycles beginning in 1860, so as to prevent a model drift for
1958 when the reanalyzed data become available.
Therefore, physical conditions before 1958 deviate from
the true state, whereas after 1958 they correspond to the
true state within the usual limitations (model errors,
forcing errors etc.).
Figure 1. Coupled REMO/MPI-OM configuration.
The red rectangle indicates the domain of
coupling. Only every fourth line of the formally
global ocean grid is shown (black line)
The “dynamical” effect of tides on the mean North Atlantic
circulation leads to a small reduction of the mean current in
the open ocean and an amplification along the North
European shelf edge.
Tidally induced mixing leads to a reduction of North
Atlantic SST. However, warming (up to 3K ) occurs near
the amphidromic points of the M2 and S2 tidal constituents
near Iceland and in the middle of the North Atlantic (Fig.2).
Figure 3. Time series of oceanic pCO2 (top) as
global mean (black line) and for the North Sea
and Baltic (red line) and oceanic uptake of
CO 2 in GtC/a (bottom)
The simulated increase in oceanic pCO2 is shown in Fig. 3
as global average (black curve) and averaged over the