Module 1. Ocean climate variations - historical time series, measurements and modelling

Participants:
Ken Drinkwater (IMR)(Module leader),Harald Loeng (IMR), Lars Asplin (IMR), Bjørn Ådlandsvik (IMR), Trond Dokken, (Bjerknes Centre), Helge Drange (NERSC), Eystein Jansen (Bjerknes Centre), Truls Johannessen (GFI,UoB), Asgeir Sorteberg (NERSC), Svein Sundby (IMR), Harald Yndestad (AUC) and Svein Østerhus (Bjerknes Centre).

Objective:
Explore the linkages between large-scale weather patterns, such as the NAO, and the regional and local climate, and investigate how such patterns cascades into spatio-temporal changes in the ocean climate parameters that are of importance for biomass production.

The objective will be approached from a broader and more interdisciplinary perspective than ever made for climate and ecosystem studies of the Barents Sea. A fully coupled global model will be used to study circulation and exchange of water masses. Emphasis will be laid on measurements of volume fluxes and ocean climate along the section Fugløya-Bjørnøya (F-B) between the Norwegian Sea and the Barents Sea. The measurements will be based on traditional hydrographic measurements, currents mooring and by analysis of paleo-proxy methods.

The module will investigate a series of cores across the F-B section with modern well preserved surface. Estimate temperature and salinity from oxygen isotopes (Martin et al. 2002; Elderfield and Ganssen, 2000) and Mg/Ca ratios and calibrate the last 100 years with the instrumental data sets from the Barents Sea. Based on the calibration, the last 1000 years will be reconstructed. Analysis of observational datasets (atmospheric reanalysis, oceanic timeseries etc.) and model simulations will form the basis of the investigations.

In addition to ongoing current measurement (under the EU-funded ASOF-N project), a bottom mounted ADCP in a trawl proof frame will be deployed in the Coastal current in order to get a complete picture of the transport of organisms to the Barents Sea. Traditional moorings are not possible due to large fishing activities in the area. Sufficient hydrographic observations will be carried out on IMR’s standard cruises.

On this array of moored current meters there will be added autonomous fCO2 measurements (SAMI’s). This will enable us to study the interaction of changing temperature, ecosystems and CO2 system. On occasional cruises the whole suit of variables of Ct, Alk, fCO2 underway and pH will be measured. In Olsen et al., submitted to Sarsia, the limitation to get accurate numbers of carbon fluxes is caused by the time resolution of data. A better timing of the development of phytoplankton blooms can be obtained by using continuous measurements, and more accurate flux estimates can be given and how this development interact with climate forcing between warm and cold years.

The model is the global fully coupled atmosphere-sea ice-ocean model called the Bergen Climate Model (BCM) (Furevik et al., 2002) which consist of the atmospheric model ARPEGE/IFS which is developed jointly by Meteo France and the European Centre for Medium Range Weather Forecast (ECMWF) and the Miami Isopycnal Coordinate Ocean Model (MICOM) including the NERSC sea ice model (Furevik et al., 2000) BCM is the first coupled global climate model with independent stretchable grids in the atmosphere and the ocean and coastlines following the different atmospheric and oceanic gridsquares.

The expected results from the module are:

• Decadal resolution time series of surface and bottom layer temperature and salinity for the last 1000 years
  
• Better understanding of frequencies in climate variability
  
• Improved transport estimates of drifting organisms to the Barents Sea related to atmospheric forcing
  
• Improved understanding of the atmospheric and oceanic processes responsible for interannual to decadal-timescale fluctuations in large-scale flow patterns that affects the advection of Atlantic Water into the Barents Sea and to which extent such fluctuations can be modified by changes in greenhouse gas forcing.
  
• Better definition of the annual to interannual flux of CO2, and its dependence on climate here defined as cold and warm years.