Trans-Atlantic Study of Calanus: Modelling the effect of large scale advection and life cycle strategies

The aim of this subtask of the Trans-Atlantic Study
of Calanus (TASC) programme was to quantify how advection
within the Norwegian Sea and life cycle strategies
(number of generations per year, developmental rate and
vertical migration behaviour) interact to produce the
distribution pattern and high production rate of this
species that is observed.

The answers to the questions addressed here can only
be achieved through a combined, basin wide hydrodynamical
model coupled to a life cycle model of C. finmarchicus.
Typically model simulations periods will be a year or
more. Since there are many uncertainties both in the
biology of Calanus and the current field when such long
term simulations are performed, model investigation will
concentrate on scenarios and sensitivity tests. Three
climatic cases will be simulated: Climatic average with
monthly mean flow field and temperatures, and two cases
with high and low inflow of Atlantic water, respectively,
using daily average flow. These simulations will be
performed by the ECOM-3D which is already established
for the area by HI. Climatological mean flow is already
available (Engedahl et al. 1995). Modelling deep
circulation depends to a large degree on a correct
density field. Improvement of the existing field by
available observations will be performed before the
last two scenarios are produced. The elements that
comprise a life cycle model (generation time,
developmental rate and vertical migration behaviour,
survival probability), are investigated in other subtasks.
The life cycle model will be of a Lagrangian type where
particles having attached state variables. Each particle
is allowed to develop (change state), die and reproduce
by spawning of new particles having state variables
typical for off-springs. Several scenarios will be
performed were parameters (and assumptions) in the life
cycle model are perturbed for each of climatic cases.