Dissolved organic carbon measured on water bottle samples at time series station DYFAMED

Dissolved organic carbon (DOC) distribution and dynamics are investigated at the DYFAMED site (central Ligurian Sea, NW Mediterranean) in relation to hydrological and biological contexts, using a 4-year time-series dataset (1991-1994). The DYFAMED site is regarded as a one-dimensional station where simple hydrological mechanisms prevail and where the ecosystem is quite well understood. An average vertical profile of DOC concentration ([DOC]) indicates that maximal concentrations and variability are concentrated in the surface layers. For depths >800 m, the annual variations are on average similar to the analytical standard deviation (~2 µM). The "composite" [DOC] distribution (average distribution over a typical year, integrating about 40 monthly profiles) for surface waters (0-200 m) is closely related to hydrological and phytoplanktonic forcings. It exhibits summer DOC accumulation in surface waters, due to spring-summer stratification and successive phytoplanktonic events such as spring and summer blooms, and winter DOC removal to deeper waters, due to intense vertical mixing. The analysis of vertical [DOC] gradient at 100-m depth as a function of the integrated DOC content in the 0-100-m layer makes it possible to objectively distinguish three specific periods: the winter vertical mixing period, the period of stratification and spring phytoplankton bloom, and the period of stratification re-inforcement and summer-fall phytoplankton bloom. We recalculate the vertical DOC fluxes to deep waters using a larger original dataset, after the first direct calculation (Deep-Sea Res. 40 (10) (1993) 1963, 1972) that was reproduced for other oceanic areas. The seasonal variations of the "composite" [DOC] distribution in surface waters are significantly correlated to the apparent oxygen utilization distribution, but the biogeochemical significance of such a correlation is still under examination. The global significance of our local findings is presented and the role of the oceanic DOC in the global carbon cycle is emphasized, especially with respect to several current issues, such as the oceanic "missing sink" and the equivalence between new production and exported production.

Hydrocarbons, sterols and alkenones at time series station KERFIX

Hydrocarbons, sterols and alkenones were analyzed in samples collected from a 10 month sediment trap time series deployed in the Indian Ocean sector of the Southern Ocean. Fluxes and within-class distributions varied seasonally. During higher mass and organic carbon (OC) flux periods, which occurred in austral summer and fall, fresh marine inputs were predominant. Vertical fluxes were most intense in January, but limited to one week in duration. They were, however, low compared with other oceanic regions. In contrast, low mass and OC flux periods were characterized by a strong unresolved complex mixture (UCM) in the hydrocarbon fraction and a high proportion of stanols as a result of zooplanktonic grazing. Terrigenous inputs were not detectable. The alkenone compositions were consistent with previous data on suspended particles from Antarctic waters. However, UK'37 values diverged from the linear and exponential fits established by Sikes et al. (1997, doi:10.1016/S0016-7037(97)00017-3) in the low temperature range. The seasonal pattern of alkenone production implied that IPT (integrated production temperature) is likely to be strongly imprinted by austral summer and fall SST (sea surface temperature).

Chlorophyll a concentration, and proportion of time in the water column obtained by instrumented bowhead whales

Sixty hours of direct measurements of fluorescence were collected from six bowhead whales (Balaena mysticetus) instrumented with fluorometers in Greenland in April 2005 and 2006. The data were used to (1) characterize the three-dimensional spatial pattern of chlorophyll-a (Chl-a) in the water column, (2) to examine the relationships between whale foraging areas and productive zones, and (3) to examine the correlation between whale-derived in situ values of Chl-a and those from concurrent satellite images using the NASA MODIS (Moderate Resolution Imaging Spectroradiometer) EOS-AQUA satellite (MOD21, SeaWifs analogue OC3M and SST MOD37). Bowhead whales traversed 1600 km**2, providing information on diving, Chl-a structure and temperature profiles to depths below 200 m. Feeding dives frequently passed through surface waters ( >50 m) and targeted depths close to the bottom, and whales did not always target patches of high concentrations of Chl-a in the upper 50 m. Five satellite images were available within the periods whales carried fluorometers. Whales traversed 91 pixels collecting on average 761 s (SD 826) of Chl-a samples per pixel (0-136 m). The depth of the Chl-a maximum ranged widely, from 1 to 66 m. Estimates of Chl-a made from the water-leaving radiance measurements using the OC3M algorithm were highly skewed with most samples estimated as <1 mg/m**3 Chl-a, while data collected from whales had a broad distribution with Chl-a reaching >9 mg/m**3. The correlation between the satellite-derived and whale-derived Chl-a maxima was poor, a linear fit explained only 10% of the variance.

(Table 1) Vertical fluxes of sediment matter and organic carbon in the Kara Sea and in the Yenisey and Ob estuaries

Sedimentary particle fluxes in the Kara Sea and in the Ob and Yenisey estuaries were first estimated and particulate matter composition was studied in September 1993 during Cruise 49 of R/V Dmitry Mendeleev. Twenty three bottom stations with sediment traps were deployed, and samples were collected from 13 stations. Particle fluxes ranged from 9.0 to 62.6 mg/m**2/day to the north of the Ob and Yenisey estuaries and were 18.7 to 62.0 mg/m**2/day in the southwestern part of the Kara Sea. Fluxes were up to 1321 mg/m**2/day in the Ob estuary and up to 22156 mg/m**2/day in the Yenisey estuary. Organic matter fluxes were estimated as 0.71-3.29, 4.28-9.04, 26.7, and 368 mg/m**2/day, respectively. Particulate matter is largely represented by pellets of planktic Crustacea and by "sea snow" flakes mainly composed of diatoms. Rapidly settling particles are extensively inhabited by bacterial flora.

(Table 1) Sea-surface temperatures, intermediate-water temperatures, and latitudinal gradient at three time slices at the end of the Cretaceous

Climatic and oceanographic variations during the last 2 m.y. of the Maastrichtian inferred from high-resolution (10 k.y.) stable isotope analysis of the mid-latitude South Atlantic Deep Sea Drilling Project Site 525 reveal a major warm pulse followed by rapid cooling prior to the Cretaceous-Tertiary boundary. Between 66.85 and 65.52 Ma, cool but fluctuating temperatures average 9.9 and 15.4°C in intermediate and surface waters, respectively. This interval is followed by an abrupt short-term warming between 65.45 and 65.11 Ma, which increased temperatures by 2-3°C in intermediate waters, and decreased the vertical thermal gradient to an average of 2.7°C. This warm pulse may be linked to increased atmospheric pCO2, increased poleward heat transport, and the switch of an intermediate water source from high to low-middle latitudes. During the last 100 k.y. of the Maastrichtian, intermediate and surface temperatures decreased by an average of 2.1 and 1.4°C, respectively, compared to the maximum temperature between 65.32 and 65.24 Ma.

(Table 2) Horizontal ice flow velocities, azimuths (relative to true north), and vertical ice-particle velocities in the vicinity of Vostok Station, Antarctica

In the austral summer seasons 2001/02 and 2002/03, Global Positioning System (GPS) data were collected in the vicinity of Vostok Station to determine ice flow velocities over Lake Vostok. Ten GPS sites are located within a radius of 30 km around Vostok Station on floating ice as well as on grounded ice to the east and to the west of the lake. Additionally, a local deformation network around the ice core drilling site 5G-1 was installed. The derived ice flow velocity for Vostok Station is 2.00 m/a ± 0.01 m/a. Along the flowline of Vostok Station an extension rate of about 10**-5/a (equivalent to 1 cm/km/a) was determined. This significant velocity gradient results in a new estimate of 28700 years for the transit time of an ice particle along the Vostok flowline from the bedrock ridge in the southwest of the lake to the eastern shoreline. With these lower velocities compared to earlier studies and, hence, larger transit times the basal accretion rate is estimated to be 4 mm/a along a portion of the Vostok flowline. An assessment of the local accretion rate at Vostok Station using the observed geodetic quantities yields an accretion rate in the same order of magnitude. Furthermore, the comparison of our geodetic observations with results inferred from ice-penetrating radar data indicates that the ice flow may not have changed significantly for several thousand years.