A compilation of global bio-optical in situ data for ocean-colour satellite applications

A compiled set of in situ data is important to evaluate the quality of ocean-colour satellite-data records. Here we describe the data compiled for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The data were acquired from several sources (MOBY, BOUSSOLE, AERONET-OC, SeaBASS, NOMAD, MERMAID, AMT, ICES, HOT, GeP&CO), span between 1997 and 2012, and have a global distribution. Observations of the following variables were compiled: spectral remote-sensing reflectances, concentrations of chlorophyll a, spectral inherent optical properties and spectral diffuse attenuation coefficients. The data were from multi-project archives acquired via the open internet services or from individual projects, acquired directly from data providers. Methodologies were implemented for homogenisation, quality control and merging of all data. No changes were made to the original data, other than averaging of observations that were close in time and space, elimination of some points after quality control and conversion to a standard format. The final result is a merged table designed for validation of satellite-derived ocean-colour products and available in text format. Metadata of each in situ measurement (original source, cruise or experiment, principal investigator) were preserved throughout the work and made available in the final table. Using all the data in a validation exercise increases the number of matchups and enhances the representativeness of different marine regimes. By making available the metadata, it is also possible to analyse each set of data separately.

Investigations on sediment coring site PS1823 in the Riiser-Larsen Sea, Southern Ocean

Physical and sedimentological investigations were carried out on a 14 m long gravity core and a 0.5 m long box core from 4440 m water depth off Queen Maud Land, East-Antarctica. Strongly bioturbated hemipelagic muds of predominantly terrigenous origin and a very small biogenic part build up the 'Normal-Facies'. Several sandy to silty layers are inserted in the 'Normal-Facies'. These layers are seperated by lithology, structure and the investigated parameters of this study and are interpreted as turbidites. The source area for the turbidity currents is supposed to be at the uppermost continental margin, close to the shelf break and there is evidenee for this gravity transport within the erosive Ritscher-Canyon, which extends close to the core position. The distribution of biogenic components indicates an age of 1.3 million years or more, with an average sedimentation rate of about 1 cm/1000 years. Early diagenetic proeesses caused water loss by compaction, errosion and dissolution of biogenic components and precipitation and recrystallization of manganese micronodules. Cyclic fluctuations of the sediment-parameters within the 'Normal-Facies' enable the distinction of a 'Glazial'- and an 'Interglazial'-Facies. The 'Glazial'-Facies reflects glacial sedimentary conditions and shows a dark olive gray colour, high susceptibility, low silt/clay-ratios, only a few biogenic components and the regular occurence of interrelated turbidite layers. In contrast, the 'Interglazial'-Facies is dominated by a light olive or olive-brown colour, low susceptibility, high silt/clay-ratios and an increased number of biogenic components. This facies corresponds to interglacial conditions. Three main processes are supposed to have been responsible for the observed facies changes: (1) the bottom water mass circulation, (2) the gravity transport by turbidity currents and (3) the biogenic surface production. These processes are related to the quaternary climatic changes. The extension of the ice shelves directed the gravity transport to the deep sea and the formation of Antarctic Bottom Water, which in turn influenced the silt/clay-ratios in the sediment record. Fluctuations in sea ice coverage controlled the biogenic surface production.

Benthic organic carbon flux and oxygen penetration depth in the Southern Ocean

For the investigation of organic carbon fluxes reaching the seafloor, oxygen microprofiles were measured at 145 sites in different sub-regions of the Southern Ocean. At eleven sites, an in situ oxygen microprofiler was deployed for the measurement of oxygen profiles and the calculation of organic carbon fluxes. At four sites, both in situ and ex situ data were determined for high latitudes. Based on this dataset as well as on previous published data, a relationship was established for the estimation of fluxes derived by ex situ measured O2 profiles. The fluxes of labile organic matter range from 0.5 to 37.1 mgC m**2/day. The high values determined by in situ measurements were observed in the Polar Front region (water depth of more than 4290 m) and are comparable to organic matter fluxes observed for high-productivity, upwelling areas like off West Africa. The oxygen penetration depth, which reflects the long-term organic matter flux to the sediment, was correlated with assemblages of key diatom species. In the Scotia Sea (~3000 m water depth), oxygen penetration depths of less than 15 cm were observed, indicating high benthic organic carbon fluxes. In contrast, the oxic zone extends down to several decimeters in abyssal sediments of the Weddell Sea and the southeastern South Atlantic. The regional pattern of organic carbon fluxes derived from micro-sensor data suggest that episodic and seasonal sedimentation pulses are important for the carbon supply to the seafloor of the deep Southern Ocean.

(Table XIV-1, Page 137-139) Physical characteristics of manganese nodules collected in the Pacific Ocean during cruise GH76-1 of R/V Hakurei Maru

Nodule samples obtained were described and studied on board for 1) observation of occurrence and morphology in and outside samplers, size classification, measurement of weight and calculation of population density (kg/m2); 2) photographing whole nodules on the plate marked with the frames of unit areas of both 0cean-70 (0.50 m2) and freefall grab (0.13 m2), and that of typical samples on the plate with a 5 cm grid scale: 3) observation of internal structures of the nodules on cut section; and 4) determination of mineral composition by X-ray diffractometer. The relation between nodule types and geological environment or chemical composition was examined by referring to other data of related studies, such as sedimentology. acoustic survey, and chemical analysis.

(Table 1) Stable isotope ratios of Globigerinoides ruber and pore water, and Cl measurement at ODP Hole 133-817C

The oxygen isotopic composition of pore waters squeezed from sediments in Hole 817C co-varies with the oxygen isotopic composition of Globigerinoides ruber below 8 mbsf. The magnitude of the variation in the pore water d18O is approximately 30% of the variation in the foraminifers. Overall, the d18O of the pore waters increases down the core, a trend that is also present in the Cl- concentrations. The variations in the d18O of pore waters may be the result of either of two phenomena. First, these may reflect original variations in the waters, the magnitude of which has been subsequently reduced by process of diffusion. Second, these may reflect recrystallization of the precursor sediment and isotopic exchange between the fluids and the recrystallized sediment. At the moment data are not available to ascertain which process is responsible although the correlation between the Cl- and the d18O data suggests that these values reflect the original composition modified by diffusion.

Distribution of coccoliths in surface sediments of the south-eastern South Atlantic Ocean

Recent coccoliths from 52 surface sediment samples recovered from the south-eastern South Atlantic were examined qualitatively and quantitatively in order to assess the controlling mechanisms for their distribution patterns, such as ecological and preservational factors, and their role as carbonate producers. Total coccolith abundances range from 0.2 to 39.9 coccoliths*10**9/ g sediment. Four assemblages can be delineated by their coccolith content characterising the northern Benguela, the middle to southern Benguela, the Walvis Ridge and the deeper water. Distinctions are based on multivariate ordination techniques applied on the relative abundances of the most abundant taxa, Emiliania huxleyi, Calcidiscus leptoporus, Gephyrocapsa spp., Coccolithus pelagicus and subtropical to tropical species. The coccolith distribution seems to be temperature and nutrient controlled co-varying with the seaward extension of the upwelling filament zone in the Benguela. A preservation index (CEX') based on the differential dissolution behaviour of the delicate E. huxleyi and Gephyrocapsa ericsonii versus the robust C. leptoporus is applied in order to detect the position of the coccolith lysocline. Although some samples were recognised as dissolution-affected, the distribution of the coccoliths in the surface-sediments reflects the different oceanographic surface-water conditions. Mass estimations of the coccolith carbonate reveal coccoliths to be only minor contributors to the carbonate preserved in the surface sediments. The mean computed coccolith carbonate content is 17 wt.%, equivalent to a mean contribution of 23% to the bulk carbonate.

Abundance of calcareous dinoflagellates of sediment cores from the South Atlantic Ocean

Despite the increasing interest in the South Atlantic Ocean as a key area of the heat exchange between the southern and the northern hemisphere, information about its palaeoceanographic conditions during transitions from glacial to interglacial stages, the so-called Terminations, are not well understood. Herein we attempt to increase this information by studying the calcareous dinoflagellate cysts and the shells of Thoracosphaera heimii (calcareous cysts) of five Late Quaternary South Atlantic Ocean cores. Extremely high accumulation rates of calcareous cysts at the Terminations might be due to a combined effect of increased cyst production and better preservation as result of calm, oligotrophic conditions in the upper water layers. Low relative abundance of Sphaerodinella albatrosiana compared with Sphaerodinella tuberosa in the Cape Basin may be the result of the relatively colder environmental conditions in this region compared with the equatorial Atlantic Ocean with high relative abundance of S. albatrosiana. Furthermore, the predominance of S. tuberosa during glacials and interglacials at the observed site of the western Atlantic Ocean reflects decreased salinity in the upper water layer.

The seasonal sea-ice zone in the glacial Southern Ocean as a carbon sink, supplementary datasets

Reduced surface-deep ocean exchange and enhanced nutrient consumption by phytoplankton in the Southern Ocean have been linked to lower glacial atmospheric CO2. However, identification of the biological and physical conditions involved and the related processes remains incomplete. Here we specify Southern Ocean surface-subsurface contrasts using a new tool, the combined oxygen and silicon isotope measurement of diatom and radiolarian opal, in combination with numerical simulations. Our data do not indicate a permanent glacial halocline related to melt water from icebergs. Corroborated by numerical simulations, we find that glacial surface stratification was variable and linked to seasonal sea-ice changes. During glacial spring-summer, the mixed layer was relatively shallow, while deeper mixing occurred during fall-winter, allowing for surface-ocean refueling with nutrients from the deep reservoir, which was potentially richer in nutrients than today. This generated specific carbon and opal export regimes turning the glacial seasonal sea-ice zone into a carbon sink.

Ice observations in the Southern Ocean between 1878 and 1928

During the period in question, large ice drifts transported incalculable numbers of icebergs, ice fields and ice floes from the Antarctica into the South Atlantic, confronting long-journeying sailing ships on the Cape Horn route with considerable danger. As is still the case today, the ice drifts generally tended in a northeasterly direction. Thus it can be assumed that the ice masses occuring near Cape Horn and in the South Atlantic originated in Graham Land and the South Shetland Islands, while those found in the Pacific will have come from Victoria Land. The masses drifting to Cape Horn, Isla de los Estados, the Falkland Islands and occasionally as far as the Tristan da Cunha Group are transported by the West Wind Drift and Falkland Current, diverted by the Brazil Current. The Bouvet and Agulhas Currents have little influence here. The great ice masses repeatedly reached points beyond the "outermost drift ice boundery" calculated in the course of the years, to continue on in the direction of the equator. The number of sailing ships which fell victim to the ice drifts while rounding Cape Horn can only be surmised; they simply disappeared without a trace in the expanses of the South Atlantic. Until the end of the 1900s the dangers presented by ice were less serious for westward-bound ships than for the "homeward-bounders" travelling from West to East. Following the turn of the century, however, the risk for "onwardbounders" increased significantly. Whether the ice drifts actually grew in might or whether the more frequent and more detailed reports led to this impression, could never be ascertained by the German Hydrographie Office. In the forty-one years between 1868 and 1908, ten light, ten medium and nine heavy ice years were counted, and only twelve years in which no reports of ice were submitted to the German Hydrographie Office. "One of the most terrible dangers threatening ships on their return from the Pacific Ocean," the pilot book for the Atlantic Ocean warns, "is the encounter with ice, to be expected south of the 50th parallel (approx.) in the Pacific and south of the 40th parallel (approx.) in the South Atlantic." Following the ice drift of 1854-55, thought to be the first ever recorded, the increasing numbers of sailing ships rounding Cape Horn were frequently confronted with drifts of varying sizes or with single icebergs. Then from 1892-94, a colossal ice drift crossed the path of the sailships in three stages. Several sailing ships collided with the icebergs and could be counted lucky if they survived with heavy damage to the bow and the fo regear. The reports on those which vanished for ever in the ice masses are hardly of investigative value. The English suffered particularly badly in the ice-plagued waters; their captains apparently sailed courses that led more freqently through drifts than did the sailing instructions of the German Hydrographic Office. Thus, among others, Capt. Jarvis' DUNTRUNE, also the STANMORE, ARTHURSTONE and LORD RANOCH as well as the French GALATHEE and CASHMERE all collided with icebergs. The crew of the AETHELBERTH panicked after a collision and took to their lifeboats. It was only after the ship detached itself from the iceberg it had rammed that the men returned to it and continued their journey. The TEMPLEMORE, on the other hand, had to be abandoned for good. Of the German sailing ships, the FLOTOW is to be mentioned here, and in the third phase of the drift the American SAN JOAQUIN lost a large proportion of its rigging. In the 20th century ice drifts continued to cross the courses of the Cape Horn ships. 1906 and 1908 were recorded as particularly heavy ice years. In 1908-09 both the FALKLANDBANK and the TOXTETH fell prey to ice, or so it was assumed during the subsequent Maritime Board proceedings. For the most part the German sailing ships were spared greater damages by sea. Their captains sent detailed ice reports to the German Hydrographic Office, which gratefully welcomed the information and partially incorporated it in the third and final edition of the "Pilot Book for the Atlantic Ocean." From the end of 1926 until the beginning of 1928, the last of the large sailing ships were once again confronted with "tremendous masses of icebergs and ice drifts." Reports of this period originated above all on the P-Liners PADUA, PAMIR, PASSAT, PEKING, PINNAS, PRIWALL and the ships of Gustav Erikson's fleet. The fate of the training sailship ADMIRAL KARPFANGER in connection with the ice in early 1938 was never clearly determined by the Maritime Board proceedings. Collision with an iceberg, however, is thought to be the most likely cause of accident. Today freight sailing ships no longer cross the oceans. The Cape Horn route is relatively insignificant for engine-powered ships and icebergs can be spotted in plenty of time by modern navigation technology ... The large ice drifts are no longer a menace, but only a marginal note in the final chapter of the history of transoceanic sailing.

Radionuclides of bulk and terrigenous surface sediments in the Southern Ocean

Sr and Nd isotopic compositions of Late Quaternary surface sediment and sediment cores from the south Atlantic and southeast Pacific sectors of the Southern Ocean are used to constrain the provenance and transport mechanisms of their terrigenous component. We report isotopic and mineralogical data for core samples from three localities, the Mid-Atlantic Ridge at 41°S and the northern and southern Scotia Sea. In addition, data for surface sediment samples from the south Atlantic and southeast Pacific sectors of the Southern Ocean are presented. The variations of Sr and Nd isotopic compositions of the bulk sediment samples in all cores were correlated with the magnetic susceptibility of the sediment and with the inferred glacial-interglacial stages. The isotopic data indicate that, during glacial periods, sediment was delivered from continental crust with a shorter residence time than that supplying material during interglacial periods. At the core site near the Mid-Atlantic Ridge, Nd isotopic, combined with mineralogical evidence indicates interglacial period deposition of a relatively high amount of kaolinite and silt with low epsilon-Nd values < -8. The material was probably supplied by North Atlantic Deep Water from low latitudes. For glacial periods, a high contribution of silt and clay with epsilon-Nd > -4.5, probably derived from southern South America, was indicated. The glacial-interglacial shift in sources may be due to either a decreasing influence of North Atlantic Deep Water during glacial times or by a larger contribution of glaciogenic detritus from southern South America. At the core site in the northern Scotia Sea, sediment of interglacial periods is dominated by smectite with epsilon-Nd < - 6 and silt with epsilon-Nd > -4. We suggest that smectite was derived from the Falkland shelf and silt was derived from the Argentinian shelf. During glacial periods, the Argentinian shelf was an important source for silt and chlorite with epsilon-Nd > -4. The contribution from the Falkland shelf seems to have remained similar during glacial and interglacial periods. Hydrographic transport by bottom currents and turbidites could account for the high glacial detrital flux. An evaluation of the significance of an aeolian contribution to deep sea sediment suggests that it plays only a minor role. In the southern Scotia Sea, the Antarctic Peninsula is considered an important source for young material with epsilon-Nd > -4, in particular during glacial periods. During interglacial periods, sediment supply from the Antarctic Peninsula was lower than during glacial times, resulting in a relatively high contribution of old material (epsilon-Nd < -8) from East Antarctica. Deep water currents and icebergs could account for the transport of the old component to the southern Scotia Sea. The accumulation rates of material from the various source regions for glacial times are in agreement with an increase in the strength of the Antarctic Circumpolar Current. The production rate and the circulation pattern of bottom water in the Weddell Sea appear to have remained similar over most of the last 150 kyr.

Zn/Sr record of the Last Interglacial Transition in South Atlantic Ocean sediments

We examined the zinc content of diatom frustules as an indicator of past changes in surface seawater Zn2+ concentration. Zn/Si data of samples from three cores located in the South Atlantic sector of the Southern Ocean spanning the last interglacial-glacial transition are presented. Changes in the Zn/Si record are linked to changes in the surface water Zn2+ concentration. The source of variation in Zn2+ concentration appears to be via changes in deep water upwelling and circulation. We rule out changes in phytoplankton productivity and aeolian dust input as a source of variation in the Zn/Si record. Likewise, the Zn/Si data are not linked to shifts in the diatom species composition of the sediment or sediment preservation effects. The Zn/Si results presented do not support the zinc hypothesis. There is no link between the uptake of CO2 by phytoplankton, as inferred from the d13C record, and the Zn/Si record.

Flux data in the Southern Ocean

Since 1983 time-series traps have been deployed in the Atlantic sector of the Southern Ocean to measure the flux of organic carbon, biogenic silica and carbonate. The organic carbon flux data are used to calculate primary production rates and organic carbon fluxes at 100 m water depth. From these calculations, annual primary production rates range from about 170 g C m**-2 in the coastal area (Bransfield Strait) to almost zero in the Permanent Sea-Ice Zone. High rates (of about 80 g C m**-2 year**-1 ) were calculated for the Polar Front Zone and rather low values (about 20 g C m**-2 year**-1 ) characterize the Maud Rise area. The estimated primary production for the entire Southern Ocean (south of 50°S), using various subsystems with characteristic carbon fluxes, is in the order of 1 * 10**9tons year**-1; the organic carbon flux out of the photic layer is 0.17 * 10**9tons year**-1. Our calculation of the Southern Ocean total annual primary production is substantially lower than previously reported values.

Measurement results of d18O, Mg/Ca, and Ti/Ca of sediment cores GeoB10042-1 and GeoB10043-3

The advection of relatively fresh Java Sea water through the Sunda Strait is presently responsible for the low-salinity "tongue" in the eastern tropical Indian Ocean with salinities as low as 32 per mil. The evolution of the hydrologic conditions in the eastern tropical Indian Ocean since the last glacial period, when the Sunda shelf was exposed and any advection via the Sunda Strait was cutoff, and the degree to which these conditions were affected by the Sunda Strait opening are not known. Here we have analyzed two sediment cores (GeoB 10042-1 and GeoB 10043-3) collected from the eastern tropical Indian Ocean off the Sunda Strait that cover the past ~40,000?years. We investigate the magnitude of terrigenous supply, sea surface temperature (SST), and seawater d18O (d18Osw) changes related to the sea level-driven opening of the Sunda Strait. Our new spliced records off the Sunda Strait show that during the last glacial, average SST was cooler and d18Osw was higher than elsewhere in the eastern tropical Indian Ocean. Seawater d18O decreased ~0.5 per mil after the opening of the Sunda Strait at ~10 kyr B.P. accompanied by an SST increase of 1.7°C. We suggest that fresher sea surface conditions have persisted ever since due to a continuous transport of low-salinity Java Sea water into the eastern tropical Indian Ocean via the Sunda Strait that additionally increased marine productivity through the concomitant increase in terrigenous supply.