Erik Buch

Greenland- Scotland Overflow studied by hydro-chemical multivariate analysis

Hydrographic, nutrient and halocarbon tracer data collected in July-August 1994 in the Norwegian Sea, the Faroe Bank Channel (FBC), the Iceland and Irminger Basins and the Iceland Sea are resented. Special attention was given to the overflow waters over the Iceland-Scotland Ridge ISOW). The Iceland-Scottland overflow water ISOW) was identified along its pathway in the Iceland Basin, and entrainment of overlying water asses was quantified by multivariate analysis (MVA) using principal component analysis (PCA) and Partial Least Square (PLS) calibration. It was concluded that the deeper portion of the ISOW in the FBC was a mixture of about equal parts of Norwegian Sea Deep Water (NSDW) and Norwegian Sea Arctic Intermediate Water (NSAIW). The mixing development of ISOW during its descent in the Iceland Basin was analysed in three sections across the plume. In the southern section at 61˚N, where the ISOW core was observed at 2300 m depth, the fraction of waters originating north of the ridge was assessed to be 54%. MVA assessed the fractional composition of the ISOW to be 21% NSDW, 22% NSAIW, 18% Northeast Atlantic Water (NEAW), 11% Modified East Icelandic Water, 25% Labrador Sea Water (LSW) and 3% North East Atlantic Deep Water. It may be noted that the fraction of NEAW is of the same volume as the NSDW. On its further path around the Reykjanes Ridge, the ISOW mixed mainly with LSW, and at 63˚N in the Irminger Basin, it was warmer and fresher (θ=2.8°C and S=34.92) than at 61°N east of the ridge (θ=2.37°C and S=34.97). The most intensive mixing occurred immediately west of the FBC, probably due to high velocity of the overflow plume through the channel, where annual velocity means exceeded 1.1 msˉ¹. This resulted in shear instabilities towards the overlying Atlantic waters and cross-stream velocities exceeding 0.3 msˉ¹ in the bottom boundary layer. The role of NSAIW as a component of ISOW is increasing. Being largely a product of winter convection in the Greenland Sea when no Greenland Sea Deep Water (GSDW) is formed, it spreads above the older and denser deep water in the Nordic Seas. Little or no GSDW, which earlier was considered to be the principal overflow water, has been formed since 1970. This shows that the Iceland-Scotland overflow may also be maintained with intermediate waters as the principal overflowing component. Decadal variability in ISOW properties has not been insignificant, as since the early 1960s there has been a decrease in salinity and temperature, by 0.06 and up to 0.5°C, respectively. Such a trend applies also to the LSW, particularly in the Irminger Basin, where it was warmer, saltier and less dense in the late 1950s and early 1960s (θ≈3.5˚C, S≈34.9,σ1.5≈34.64 kgmˉ³) than in 1994 (θ≈2.9˚C, S≈34.86,σ1.5≈34.69 kgmˉ³)CFC tracers were used to assign apparent ages of water masses, showing that the NSDW had an apparent age of about 30 years and that the age of Iceland Sea Deep Water exceeded 25 years. NSAIW observed in the southern Norwegian Sea was estimated to be 6-16 years old. An upper age limit of LSW in the Iceland Basin was found to be 18-19 years. It was further concluded that the products of the onset of intense wintertime convection in the Labrador Sea in the late 1980s were not yet observed in the northern central part of the Iceland Basin. The LSW in the Irminger Basin was found to be significantly younger. Two layers were found there. A shallower layer at a depth of 1000-1500 m depth was older than the layer beneath by about 4 years, while the deeper layer at 1500-1800 m depth was assessed at an apparent age ranging between less than 1 (formed during the previous winter) and 4 years.

Observed transport estimates between the North Atlantic and the Arctic Mediterranean in the Iceland–Scotland region

The Arctic Mediterranean is the ocean area north of the Greenland-Scotland Ridge. Exchanges between this region and the North Atlantic both provide the main source for production of North Atlantic Deep Water and supply heat and salt to the northern oceans. The exchange occurs through several gaps in the ridge; in terms of volume flux the Iceland-Scotland Gap is the most important one as it carries more than half the total, with approximately three quarters of the total inflow and one third of the total outflow. The Nordic WOCE observational system was initiated to monitor the exchanges through this gap and it has provided data that allow estimates of typical fluxes and their seasonal variation. The flux measurements show that most of the Atlantic inflow to the Arctic Mediterranean returns as overflow and hence the processes forming intermediate and deep waters in the Arctic Mediterranean are the main forcing mechanism for the Atlantic inflow. The inflow between Iceland and Scotland seems to be a maximum in late winter while the Faroe Bank Channel overflow is strongest in late summer. Using the results from the Nordic WOCE system it has been possible to interpret historical observations from Ocean Weather Ship Station M and conclude that the flux of the Faroe Bank Channel overflow decreased in magnitude from 1950 to 2000.

Danish Attitudes and Reactions to the Threat of Sea-Level Rise

Abstract The Danish coastline has continually changed since the last ice age with relative subsidence in the south and uplift in the north. The result is a low-lying country with raised beaches and wide marine forelands in the north and an archipelago in the south. The coastline is relatively long (7400 km) for an area of 42,000 km2. Eighty percent of the population of 5.33 million (1 January 2000) live in municipalities with a coastline. Vulnerable low-lying areas contain 60,000 to 70,000 properties. These areas are mainly raised sea floor, marshes, and reclaimed areas. On the basis of present vertical movements and projected global accelerated sea-level rise (ASLR) it is estimated that relative sea level will increase by 33–46 cm within the next 100 years—notably in the southwestern part of Denmark. Increased storm intensity may enhance the impacts of this change in water level. Dikes protect about 1100 km of the coastline and hard structures about 700 km. Soft solutions, especially beach nourishment, are increasingly used. So far direct planning for sea-level rise above the current secular rise has been modest and purely qualitative. The same applies to most new and upgraded coastal infrastructure, where the approach has largely been a “wait and see” attitude. Economical evaluations have been either unofficial or absent. More attention has been paid to the impacts on coastal ecosystems, especially saltmarshes and sand dunes. Here the choice of action will depend on attitudes to and weighing of economic, sociological, and biological interests and options. The general strategy appears to be toward the preservation of a natural coastline, if necessary at the cost of land loss.

Integrated marine science in European shelf seas and adjacent waters

The European Shelf sea Integrated Project (ESIP) and Integrated infrastructure for European Research Area in Marine Science (SERAM) are two proposed integration activities to establish an integrated, world-leading operational modelling and observing system in European shelf seas and adjacent waters. The ESIP-SERAM system is consti- tuted by an integrated next generation operational modelling system, supported by an integrated marine observing system, a data exchange system, distributed data centres and a service system. It will serve as an efficient tool to transfer state-of-the-art marine science and technology into valuable information products for end-users, especially for: 1. operational agencies with value added forecast products and new forecasting capabil- ities 2. environmental monitoring agencies with optimised monitoring strategies 3. regional environmental protection organisations such as HELCOM and OSPARCOM with high quality and fast delivered environmental indicators (rapid environment assessment) 4. GMES with a full set of operational (near) real-time in situ marine observations in major parts of the marine Economic Exploration Zone in 15 countries (9 EU member countries and 6 associated countries) 5. being an integrated infrastructure basis for European Research Area in marine science.

Forecasting the Baltic

Publisher Summary This chapter describes the establishment of a Baltic Operational Oceanographic System (BOOS) for forecasting the Baltic. The task of BOOS is to design and implement an optimal operational observing system for the Baltic Sea area and the development and implementation of an efficient system for the exchange of real-time data. Project groups have been established to design an optimal observation plan for real-time observations of sea surface temperatures, waves, currents, harmful algae, and chemical parameters. The BOOS group has established a working group with the task to develop an efficient system for exchange of real-time data. The BOOS group has implemented a BOOS homepage with linkage to relevant products at national centers. This service was developed further in 1999 to include real-time presentations of water level data from selected stations in the Baltic. The implementation of operational models for the BOOS area has started at a number of institutions. A project with the aim to improve the performance of the current operational model systems for the Baltic Sea is also proposed in the chapter.

Oceanographic monitoring network in the Danish waters

The Royal Danish Administration of Navigation and Hydrography (RDANH) is the organisation responsible for navigational safety in the Danish, Faroese and Greenlandic waters. For many years this responsibility has implied: u * hydrographic surveying * establishment and maintainance of lighthouses and buoys for shipping guidance * operation of various radio navigation systems such as Decca, Sylidis, Loran-C and recently DGPS * piloting * organisation of the coastal rescue service In 1990 an additional activity was added with the establishment of a Physical Oceanographic Department responsible for the collection, analysis and distribution of oceanographic data. This activity serves two purposes: firstly to support the Hydrographic Surveying Department with oceanographic data (water level, currents and sound velocity profiles) needed for quality control of their data and secondly to improve the navigational safety in the Danish waters by communicating real time data on water level, current velocity and direction, waves, buoyancy and wind speed and direction. A network of 13 stations water level stations were established in 1991. Measurements are performed every 15 minutes with realtime and data transfer to the cental storage database in Copenhagen via the public data network. In 1995 and early 1996 six oceanographic stations have been established. These stations are equipped to measure current velocity and direction at six depth levels, wind speed and direction and the vertical distribution of temperature and salinity in the water column. The measuring interval is 30 minutes with realtime data transfer to the database. The oceanographic data stored in the database are subsequently quality controlled and can be accessed for other tasks such as environmental monitoring, scientific research, construction work. The oceanographic data are communicated to navigators by the personnel manning the Drogden Lighthouse and the Great Belt and Drogden Vessel Traffic System (VTS) centers. In 1996 the RDANH has also established a Recorded Information Service with the purpose of, serving recreational mariners with oceanographic data. The RDANH has received positive feedback from commercial as well as recreational mariners, regarding the operational, oceanographic service, who are all very satisfied with the availiability of real time data on the oceanographic conditions. The next logical task will be to establish a prediction model of the oceanographic conditions in the Danish Straits. To fulfill this task the RDANH has joined a modellign group established under HELCOM.

Atlantic Ocean Observing Networks: Cost and feasibility study

Results of a cost and feasibility study of the present and planned integrated Atlantic Ocean Observing System, including assessing the readiness and feasibility of implementation of different observing technologies