Nordsee und Deutsche Bucht 2002 
BSH 
9 
Summary 
This document is the pilot edition of the Oceanographic Status Report for the North Sea and 
German Bight that will be published annually by BSH. While the qualifier oceanographic may 
appear too broad-scale, for the pilot report largely restricts itself to physical state variables, it 
provides an appropriate roof for future contributions from other oceanographic fields. In parti 
cular, work is underway to accommodate results from the BSH's marine chemical monitoring 
beginning with the next issue. 
The oceanographic state in 2002 is documented by recent observations and modeling data. 
If climatological or other reference data exist or could be acquired, the state is assessed. 
Where these prerequisites to a firm assessment are lacking, an educated guess at the qua 
lity of the state is attempted from limited knowledge of physical processes and interrelations. 
A complete 4-dimensional spatiotemporal documentation - let alone an assessment - of the 
oceanographic state is not currently possible. The only realistic perspective to eventually get 
reasonably close to this goal is rigorously validated, dependable models. In addition, such 
models need to employ data assimilation techniques to imbed and enhance oceanographic 
observations, in particular satellite data, in ocean state simulations. 
North Sea 
The spatiotemporal evolution of the oceanographic state is governed by variations in 
atmospheric boundary forcing. The most important single factor of influence during the cold 
season is the North Atlantic Oscillation (NAO) quantified through an NAO Index. In 2002, the 
NAO performed oscillations about a high positive level through mid-summer before 
experiencing a sharp drop to its negative phase in September that was followed by an 
amplified oscillation around a flat level. A phase portrait of dynamical NAO states since 1879 
shows three regions of attraction which appear associated with decade-long and sponta 
neously changing preferences of the NAO for its negative and positive phase, respectively. 
The seasonal circulation in 2002 is described by velocity fields from BSH's operational 
model. Currents were strongly developed and highly persistent in winter and fall but weak 
and changeable in spring and summer. Whether departures in intensity and pattern from 
external model climatologies are attributable to anomalous atmospheric forcing or model 
deficiencies cannot presently be resolved. 
Sea surface temperature (SST) is the best observed ocean state parameter worldwide. 
Weekly SST analyses for the North Sea have been carried out at BSH since 1968. It turned 
out that the overall annual mean SST of 11.0 °C for 2002 not only is the highest on record 
but also marks the ad interim climax of the current intense warm episode that jumped into 
existence in 1989. The abrupt termination of the preceding decade-long cold phase was 
accompanied by an extreme NAO + event. Geographical distributions of monthly SST 
anomalies in 2002 show that SSTs were considerably above normal both throughout the 
year and next to basin-wide. 
Geographical distributions of sea surface salinity (SSS) are estimated from observational 
data collected during monitoring cruises in January/February and July. The Atlantic influx in 
the north was more intense in comparison to preceding years, the Fair Isle current was 
abated, and transports of Atlantic water through the English Channel were low. The summer 
distribution (prior to the flood event of Elbe river) reflects the spread almost throughout the 
eastern half of the North Sea of increased continental runoff and Baltic outflow in winter. 
Extensive spreading is corroborated through six vertical west-east salinity transects. 
Nutrient data obtained from the same cruises are presented geographically for near-surface 
and bottom levels. Vertical differences in concentration are small in winter, when the North 
Sea is well mixed. In summer, notable differences above and beneath the discontinuity layer