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MAIA - Monitoring the Atlantic Inflow toward the Arctic

Summary information

Funding:FP5 - Research project
Total cost:2393050
Ec contribution:1183500
Start date:2000-01-01
End date:2003-01-01
Duration:36 months
Coordinator:Thomas McClimans (
Organisation:SINTEF Fishery and Aquaculture, Trondheim – Norway
Themes:Ocean current changes; temperature changes
Regio:Arctic; North Atlantic
Keywords:Forecasting; Meteorology; Resources of the Sea; Fisheries; Environmental Protection; Measurement Methods
Project name:MAIA - Monitoring the Atlantic Inflow toward the Arctic
Project summary:Abstract
The overall objective of MAIA is to develop an inexpensive, reliable system for monitoring the inflows of Atlantic water (AW) to the northern seas. The method employs a geostrophic balance between the Coriolis force on the flow and the pressure (sea-level) difference across the flow for variations that are much slower than a day. Due to the Coriolis effect, the poleward flow causes the surface to rise to the right toward the coast. The flow of AW through the Norwegian Sea comprises an offslope baroclinic transport and a barotropic shelf slope jet. The inflow past the Faroes contains a combined barotropicbaroclinic jet. MAIA aims to monitor the inflow of AW and associated velocities on the continental shelves to an accuracy of 15% of the total values and a time resolution down to 5 days. This accuracy and resolution, using the proposed method, has been earlier demonstrated for shelf slope currents. The 5-day averaging eliminates the effects of tides and synoptic meteorological effects. The region of interest extends from the Rockall Trough in the southwest to the Kara Sea in the northeast. In the north, the project focuses on monitoring the flows through the Barents Sea. The effects of the inflows on the ice fronts in the north are studied. There are several variables to take into account when using the MAIA concept. From earlier work, the buoyancy of the coastal water and the atmospheric pressure (inverse barometer) near the tide gauges are taken into account. This gives the coastal signal of the AW inflow, but both in situ data from 1975 to 2000 and satellite altimetry have revealed several other physical aspects of the ocean circulation that must be considered. These include significant motions in the deeper layer, wind, a buoyant surface layer outside the AW front, variable density of the AW inflow and a variable external water level. The original paradigm was based on a simple 2-layer flow off Norway, where the barotropic slope jet and the baroclinic frontal jet are geographically separated. The distribution to the north of the Faroes is more complicated, with a mixed barotropic baroclinic slope jet. For this region, it has been possible to resolve the modes using EOF. Here, there appears to be a relatively constant, but noisy, division between baroclinic and barotropic parts throughout the year. This is believed to be a result of the topographical constraints imposed by the Iceland-Faroe Ridge. Algorithms for computing the inflow were developed in MAIA WP3 (2002) on the basis of historical data from 1975 to 2000. A major result of the historical analysis is the demonstration of disparate, latitude-dependent seasonal phases for the baroclinic and barotropic flows. The algorithms in MAIA WP3 (2002) were linear regressions.

Results from a validation experiment from June 2000 to November 2001 are used to validate the earlier algorithms and to resolve several issues. In general, the early algorithms had very limited predictive capability. In this experiment both currents and bottom pressures are used to estimate the inflows, and drifters and tracers are used to gain insight into the influence of the outer domain. The results have resolved, in part, the seasonal disparities. In the newer work we have made improvements in the algorithms by accounting for the quadratic relation between baroclinic transports and water level rise across the current, by including satellite altimetry closer to the shelf slope and by accounting for the effect of winds near the coastal stations. Based on these findings, revised algorithms are proposed and recommendations are made for improvements in the method to capitalise on the available monitoring data. A time series of estimated monthly averaged Atlantic water inflow toward the Arctic is presented for the period 1978-2002. We have reduced the noise level for predicting flows on the basis of coastal water level data by employing more monitoring data. To reduce the noise further, it is recommended to expand the monitoring by employing telemetering bottom pressure sensors at strategic locations. Bottom pressure sensors located in regions with significant baroclinic flows need the support of inverted echo sounders and seasonal hydrography to record the actual water level. This report and all other MAIA deliverables are included in the MAIA CD-ROM that is issued by BODC.

Use of MAIA results
The potential results of MAIA for predicting sea surface temperature and ice-front position over weeks, based on transports of warm Atlantic Water to the region of interest, could enhance long-term weather forecasting.

For the petroleum industry MAIA can provide a means to calculate the long-term variability of the Atlantic inflow to put short-term measurements into perspective. This will lead to more reliable estimates of extreme current speeds in areas where it is an important design parameter. MAIA can also provide more reliable boundary conditions for numerical models of the shelf seas from the North Sea to the Kara Sea, north of Siberia, and improve their value as a forecasting tool for operational purposes, as well as a tool for establishing longterm data series of ocean currents. The results can also provide a correlation between easily observable oceanic parameters and the ice extent in the Barents Sea, which can be used for ice cover forecasts on a time scale of months to seasons.

Commercial fisheries are pursued in sea areas influenced by the Atlantic inflow to the Arctic by the European Community, Nordic and Russian Federation nations. These fisheries are of great socio-economic importance and have in the past been managed by international agreements based upon annual scientific stock assessments and population predictions. There is a growing impetus towards introducing multi-species interactions and environmental influences to fisheries management.

As for the environment, the transport routes for Atlantic water toward the Arctic will provide valuable information for assessing the fate of pollutants in northern European shelf seas. The results of MAIA are directly relevant to the World Climate Research Programme's climate studies: Arctic Climate System Study (ACSYS) / Climate and Cryosphere Programme (CliC) and Climate Variability (CLIVAR).

The European component of the Global Ocean Observation System (EuroGOOS) is concerned with identifying the potential synergy from a range of measurements. It has a strong and continuing interest in measuring the strength of the thermohaline circulation, monitoring deepwater formation, convection, and northward transport. MAIA represents first and foremost added value to existing measurement/monitoring programmes.
Project outputs:BODC had responsibility for assembling and fully documenting all data collected during the validation experiment. The data set consists of 859 CTD casts, 18 moored ADCPs, 43 current meters, 6 bottom pressure recorders, 2 inverted echo sounders, 8 RAFOS floats and 1 Iodine experiment.

The full MAIA data set was published on CD-ROM by BODC in March 2003 complete with user interface and documentation (see project website for more information and to obtain a data CD).