Modelling the exceptional Baltic Sea inflow events in 2002-2003

During 2002 and 2003 exceptional inflow events have been registered. In January 2003 a massive inflow of highly saline, cold and extremely oxygen‐rich water from the North Sea was recorded at Darss Sill. This event is considered to be the most important inflow since 1993. A coupled model system for the Baltic Sea region, called BALTIMOS, was developed in the frame of DEKLIM/BALTEX by linking existing model components for the atmosphere (model REMO), for the ocean including sea ice (model BSIOM), for the hydrology (model LARSIM) as well as for lakes. The model system consists of high resolution model components: 1/6° (∼18 km) with 20 vertical levels; ocean‐ice 5 km with 60 vertical levels, hydrology 1/6°. The model domain covers the whole drainage basin of the Baltic Sea as well as major parts of Europe. The exceptional inflow events have been simulated successfully with BALTIMOS. The simulation was initialized at 1st of February 2002 and the model has been run until October 2003. This period includes the exceptional warm water inflow in autumn 2002 and the major Baltic inflow in January 2003. Different inflow characteristics are presented and discussed. The simulated volume transport for the major inflow in January 2003 amounts to about 250 km3, half of which was of salinity 17 PSU which corresponds to a salt transport of 2.7 × 1012 kg

Loss of sea ice during winter north of Svalbard

Sea ice loss in the Arctic Ocean has up to now been strongest during summer. In contrast, the sea ice concentration north of Svalbard has experienced a larger decline during winter since 1979. The trend in winter ice area loss is close to 10% per decade, and concurrent with a 0.3°C per decade warming of the Atlantic Water entering the Arctic Ocean in this region. Simultaneously, there has been a 2°C per decade warming of winter mean surface air temperature north of Svalbard, which is 20–45% higher than observations on the west coast. Generally, the ice edge north of Svalbard has retreated towards the northeast, along the Atlantic Water pathway. By making reasonable assumptions about the Atlantic Water volume and associated heat transport, we show that the extra oceanic heat brought into the region is likely to have caused the sea ice loss. The reduced sea ice cover leads to more oceanic heat transferred to the atmosphere, suggesting that part of the atmospheric warming is driven by larger open water area. In contrast to significant trends in sea ice concentration, Atlantic Water temperature and air temperature, there is no significant temporal trend in the local winds. Thus, winds have not caused the long-term warming or sea ice loss. However, the dominant winds transport sea ice from the Arctic Ocean into the region north of Svalbard, and the local wind has influence on the year-to-year variability of the ice concentration, which correlates with surface air temperatures, ocean temperatures, as well as the local wind

Remote and local monitoring of dissolved and suspended fluorescent organic matter off the Svalbard

Distribution maps of CDOM and algal pigments, both in superficial and deep waters, have been obtained operating a portable dual laser spectrofluorometer and a lidar fluorosensor equipments for the first time during two polish AREX oceanographic campaigns in 2006 and 2007 summertime in the Svalbard area. The different hydrological regimes strongly affected the biological factors in the waters around the Svalbard Islands as monitored during the campaigns with strong regional differentiations between the two years. The occurrence of large phytoplanktonic blooms and patches have been observed in the western area of the Spitsbergen Island coastline due to the nutrient release from pack ice and/or iceberg melting with values of more than 10 µg/l in both campaigns. Different CDOM fractions have been monitored with the remote and local instruments and inverse proportionality with salinity is confirmed along the water column. Phycobilin pigments, as phycoerythrin and phycocyanin accessory algal pigments, have been monitored in the northern area as well as tyrosine and tryptophan protein-like fluorescence distribution. The double filtration, performed with the dual laser spectrofluorometer, allows to retrieve the small fluorescence contribution due to NADPH and carotenoids pigments in the blue fluorescence emission. Successively, the large spectroscopic data base has been critically analyzed with a robust statistic instrument, thus identifying different marine provinces and retrieve distinctive CDOM fractions

A water column study of methane around gas flares located at the West Spitsbergen continental margin

In the Arctic Seas, the West Spitsbergen continental margin represents a prominent methane seep area. In this area, free gas formation and gas ebullition as a consequence of hydrate dissociation due to global warming are currently under debate. Recent studies revealed shallow gas accumulation and ebullition of methane into the water column at more than 250 sites in an area of 665 km2. We conducted a detailed study of a subregion of this area, which covers an active gas ebullition area of 175 km2 characterized by 10 gas flares reaching from the seafloor at~245 m up to 50 m water depth to identify the fate of the released gas due to dissolution of methane from gas bubbles and subsequent mixing, transport and microbial oxidation. The oceanographic data indicated a salinity-controlled pycnocline situated ~20 m above the seafloor. A high resolution sampling program at the pycnocline at the active gas ebullition flare area revealed that the methane concentration gradient is strongly controlled by the pycnocline. While high methane concentrations of up to 524 nmol L−1 were measured below the pycnocline, low methane concentrations of less than 20 nmol L−1 were observed in the water column above. Variations in the δ13CCH4 values point to a 13C depleted methane source (~−60‰ VPDB) being mainly mixed with a background values of the ambient water (~−37.5‰ VPDB). A gas bubble dissolution model indicates that ~80% of the methane released from gas bubbles into the ambient water takes place below the pycnocline. This dissolved methane will be laterally transported with the current northwards and most likely microbially oxidized in between 50 and 100 days, since microbial CH4 oxidation rates of 0.78 nmol d−1 were measured. Above the pycnocline, methane concentrations decrease to local background concentration of ~10 nmol L−1. Our results suggest that the methane dissolved from gas bubbles is efficiently trapped below the pycnocline and thus limits the methane concentration in surface water and the air–sea exchange during summer stratification. During winter the lateral stratification breaks down and fractions of the bottom water enriched in methane may be vertically mixed and thus be potentially an additional source for atmospheric methane

Duration of female parental care and their survival in the little auk Alle alle - are these two traits linked?

Desertion of offspring before its independence by one of the parents is observed in a number of avian species with bi-parental care but reasons for this strategy are not fully understood. This behaviour is particularly intriguing in species where bi-parental care is crucial to raise the brood successfully. Here, we focus on the little auk, Alle alle, a small seabird with intensive bi-parental care, where the female deserts the brood at the end of the chick rearing period. The little auk example is interesting as most hypotheses to explain desertion of the brood by females (e.g. “re-mating hypothesis”, “body condition hypothesis”) have been rejected for this species. Here, we analysed a possible relationship between the duration of female parental care over the chick and her chances to survive to the next breeding season. We performed the study in two breeding colonies on Spitsbergen with different foraging conditions – more favourable in Hornsund and less favourable in Magdalenefjorden. We predicted that in Hornsund females would stay for shorter periods of time with the brood and would have higher survival rates in comparison with birds from Magdalenefjorden. We found that indeed in less favourable conditions of Magdalenefjorden, females stay longer with the brood than in the more favourable conditions of Hornsund. Moreover, female survival was negatively affected by the length of stay in the brood. Nevertheless, duration of female parental care over the chick was not related to their parental efforts, earlier in the chick rearing period, and survival of males and females was similar. Thus, although females brood desertion and winter survival are linked, the relationship is not straightforward