Intercomparison of dynamic height in the Nordic Seas from observations and climate model

• Main Authors: Helge Drange, Er Korablev, Johnny A. Johannessen, Yongqi Gao, Ola M. Johannessen
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Barents Sea; Greenland; Norway; Norwegian Sea; Greenland Sea; Nordic Seas; Northeast Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.596.9637; http://earth.esa.int/workshops/goce04/participants/185/paper_johnny_goce_proceed.pdf

The dynamic height D, defined as the product of the depth difference between two surfaces of constant pressure and gravity, is used for estimation of the ocean circulation at both regional and global scales. The dynamic height can be readily derived from 3-dimensional observations of temperature and salinity (i.e., from hydrography), or from Ocean General Circulation Models (OGCMs). It can also be derived from remotely sensed sea surface height and the Earth's geoid. In this study, which is a part of the OCTAS project supported by the Research Council of Norway, and the GOCINA project supported by the EU, a unique Russian data set with about 127.000 hydrographic observations covering the 20th century has been used to compute the mean value and the decadal variability of D of the Northeast Atlantic and Nordic Seas (Norwegian Sea, Greenland Sea and Barents Sea). Similar computations are made from an ocean general circulation model (OGCM) driven by daily NCEP atmospheric forcing fields from the period 1948 to present. Analyses of the observed and simulated D-fields show fairly good temporal and spatial similarities. It is particularly evident that D varies on decadal time scales. Moreover the degree of variability in the region over the last 50 years is quantified. This quantification is of importance as it provides bounds on the accuracy required by remotely sensed sea surface height and the Earth's geoid fields for reliable estimates of the ocean circulation.