Elisabet Fogelqvist

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.

Photobleaching of fluorescence and the organic carbon concentration in a coastal environment

Abstract In order to investigate the photobleaching potential of estuarine waters from different depths and redox conditions and with varying degree of biological activity, filtered, unfiltered and chloroform-poisoned water samples from the Baltic Sea were exposed to ambient sunlight. Fluorescence, at excitation 350 nm and emission 450 nm, was used as an indication of humic substance concentration. Fluorescence and organic carbon concentration were measured at regular time intervals during light exposure. We found that the decrease in humic substance fluorescence can be fitted to an exponential decay function. The fluorescence half-lives were within the range 0.4 – 4.6 days in different water masses, with fluorescence decreasing to between 20% and 60% of initial concentration, respectively. Results from the curve fitting procedure indicate a rest concentration of humic substance fluorescence, similar among the sampled sites, that is resistant to further photochemical degradation. The largest relative decreases in fluorescence were found in deep waters, but samples from deep waters also had a higher fluorescence rest concentration than samples from surface waters. Biological activity was reduced by filtering the samples through 0.2μm pore size filters or adding chloroform. No statistically significant differences were found after 3 days of irradiation between samples with and without treatment to reduce biological activity. The highest initial fluorescence values and the largest fluorescence decrease were found in the anoxic waters of the Gotland Deep. The organic carbon concentrations decreased 3–7% at all stations. The shortest half-life of humic substance, and the largest decrease in organic carbon concentrations, were found in samples from the northern basins of the Baltic Sea.

New sheathless interface for coupling capillary electrophoresis to electrospray mass spectrometry evaluated by the analysis of fatty acids and prostaglandins

A new interface for capillary electrophoresis electrospray ionization (CE-ESI) is presented. High voltage is applied at the outlet of the separation capillary by a stainless steel tube, a so called liner, through which the capillary is led. A compensating current between the liquid and the liner is maintained by a natural liquid film, which is built up at the outer surface of the capillary end. Operable potential ranges for differently treated capillary ends have been examined. The liner has been evaluated for the analysis of fatty acids and prostaglandins, all run with the ESI in the negative ionization mode. This simple stainless steel liner should fill the gap, which has prevented CE-MS from being the successful tool, which it has the potential for, namely fast and unattended measurements of analytes in the nM range in complex mixtures.

Apparent removal of the transient tracer carbon tetrachloride from anoxic seawater

Two chlorofluorocarbons (CFC-11 and carbon tetrachloride, CCl4) widely used as tracers for dating water masses, were measured in the Gotland Basin of the Baltic Sea. At the time of the survey, the bottom water of the basin had remained stagnant for 15 years and anoxic for about the same period of time, and the concentrations of both CFC-11 and CCl4 decrease dramatically with depth below the mixed layer. Furthermore, the ratio of CFC-11 to CCl4 increases with depth under the mixed layer along with a steep decrease in oxygen concentration. This is contrary to what would be expected from the atmospheric histories. The most plausible explanation for this is that there is a mechanism whereby the CCl4 is removed from the water mass under anoxic and suboxic conditions.

The distribution of man-made and naturally produced halocarbons in a double layer flow strait system

The Bosphorus Strait, which connects the Black Sea and Mediterranean Sea via the Marmara Sea, is characterised by two distinct water masses. The upper layer consists of low density Black Sea water (sigma-t 10-11) flowing southward, and it is underlain by high density water (sigma-t >28) of Mediterranean origin flowing northward. The sharp density gradient between the two layers is due to the difference in salinities. Here we report measurements on a suite of low molecular weight halocarbons together with basic hydrographic parameters in the strait. Concentrations of the transient tracers chloroftuorocarbons CFC-11 (CFC13), CFC-113 (CC12FCCIF2) and carbon tetrachloride (CCI4) were highest in the Cold Intermediate Black Sea Water (CIBSW), which is formed in the Black Sea during winter. This layer disappeared within the contraction region of the Bosphorus where a hydraulic jump occurs. The Marmara Sea deep water at the entrance to the Bosphorus Strait carried low amounts of CFCs indicating an equilibrium with the atmosphere 6-11 years earlier. Varying amounts of other halocarbons such as chloroform (CHCI3), dibromomethane (CH2Br2), methyl iodide (CH3I) and chloro-iodomethane (CH2CII) could be used for the identification of water masses of different origin. Around the Bosphorus- Marmara Junction (BMJ) in the Istanbul area, the upper water layer contained elevated levels of most of the halocarbons. This is attributed not only to contamination but also to natural production in the productive eutrophic waters of the region. Methyl iodide and chloro-iodomethane showed elevated concentrations of 0.7~).9 ng/l and 0.4-0.6 ng/l, respectively, in the upper water layer of the BMJ region, and also in near-bottom water at the northern exit of Bosphorus (0.2 and 0.1 ng/l, respectively). Chloroform (23 ng/l) and dibromomethane (10 ng/I) were also found within the pycnocline in the BMJ region and could be traced in a plume stretching northward along the pycnocline. Copyright

Comparison of dynamic fast atom bombardment/liquid secondary ion mass spectrometry and electrospray mass spectrometry coupled to reversed-phase liquid chromatography for the determination of oligosaccharides in seawater

Abstract A method has been developed for determination of non-derivatised oligosaccharides by LC–MS at low concentration levels and in complex matrices of seawater and sediment pore water. Two ionisation techniques, dynamic fast atom bombardment (FAB)/liquid secondary ion (LSI) MS and electrospray ionization (ESI), were investigated and evaluated. The electrospray using Li + ions as adducts proved to be superior to the FAB/LSI-MS for the determination of non-derivatised oligosaccharides. The LC separation was accomplished by the use of a C 18 column and the elution either by a gradient of methanol–acetonitrile–water or pure water, in which latter case the column was held at an elevated temperature. We also report results from measurements of oligosaccharides in pore waters of marine sediment cores. Oligosaccharides of a range from 2 to 6 sugar units were found in a concentration range of 2–100 n M , the smaller sugars being more abundant. The depth profiles in the sediment cores indicate a production in the redox boundary layer and from there, diffusion in both directions to the overlaying water and further down into the sediment.