Hydrographic boundary conditions


Helgoland is the only North Sea island of more than 40 km distance to the nearest costline, a true off-shore island.
The tidal regimes and the variable wind-conditions influence the advection to the position Helgoland Roads.

The mean residual current passes the island counter-clockwise

Figure 1: Percentage of Origin of the Particle-Distribution virtually sampled at Helgoland Roads
from 1975 to 1994 after a 14 days drift
(calculated with DRIFT, a drawer model for the German Bight,
Reiners, Greve and Müller-Navarra, unpubl.)

Figure 2: The 14 days trajectories for the single plankton samples visualise the specific three dimensional sources.
At easterly winds upwelling is observed near Helgoland Roads

Figure 3: Temperature distributions observed from Satellite (BSH) visualise potential influences from the english Channel on the south east of the north sea.

Figure 4: The multi annual temperature distribution at Helgoland Roads indicating a strong relative variance in winter
and a reduced realtive variance in spring, summer and fall. Winter temperatures influence the seasonality of many
zooplankton populations (see prognosis).