Radiocarbon ages measured in core PSh63-5159R from the southwest Barents Sea

Environmental changes in the surface and bottom water layers of the Ingøydjupet Basin and history of Atlantic water inflow to the southwestern Barents Sea during the last 16 ka are reconstructed on the base of planktic and benthic foraminiferal assemblages. A multiproxy study of sediment cores PSh-5159R and PSh-5159N, including AMS 14C dating, provides time resolution of about 200 years for the deglaciation period, 100 years for Holocene, and 25-50 years for the last 400 years. Stable polar conditions with sea ice on the surface were typical for the early deglaciation period. Unstable bottom settings and onset of ice rafting marked Oldest Dryas. Cold Atlantic water inflow increased notably during the Boiling-Allerod interstadial nearby the site location and then decreased during the Younger Dryas. Early Holocene was characterized by abrupt warming in the bottom and surface water layers, especially ~9.7-7.6 ka BP. Stable conditions prevailed during Middle Holocene. Remarkable changes in the sea-surface temperature and bottom environments occurred during last 2.5 cal. ka BP.

Stable oxygen and carbon isotopic composition of foraminifera and sea water from the Arctic Ocean

O18/O16 data on a depth profile of water samples from the Arctic Ocean reveal that near surface water is depleted in O18 by about 4 per mil, but water at depths greater than 350 meters reaches near normal open ocean water composition. The O18 profile very closely follows the salinity profile, with deltaO18 changing by about 0.8 per mil per 1 per mil salinity change. The results of deltaO18 measurements on the pelagic species Globigerina pachyderma from a composite core show that the deltaO18 value has not changed since the latter part of the last glacial period. This constancy we take to indicate that the temperature and the deltaO18 value of the water in which these foraminifera grew have not changed significantly since that time. Such a conclusion seems to imply that the present ice coverage in the Arctic Ocean has remained unchanged during the last 25,000 years. However, the deltaO18 value of benthonic foraminifera shows a shift of 1.2 per mil between the end of the last glacial period and the present warm period. This shift is consistent with the idea that the deep water mass of the Arctic Ocean is formed outside the Arctic basin. The information on the deltaO18 value of the benthonic foraminifera from the top of the core was used in conjunction with the data on deltaO18 and temperature of the bottom water to establish the constant in the empirical equation relating deltaO18 values to temperature for the preparation procedure used in our laboratory. Based on this calibration, the data confirm A. W. H. Bé's contention (personal communication, 1960) that G. pachyderma incorporates about one-half of its CaCO3 below 300 meters.

Calcium carbonate conctent and stable isotope ratios of glacial-holocene sediments from the South China Sea

A bathymetric transect of cores in the South China Sea extending from 4200-m to less than 1000-m water depth has been examined for glacial-interglacial changes in carbonate and organic carbon sedimentation. Typical 'Pacific carbonate cycles' (high carbonate content during glacials and low carbonate content during interglacials) characterize cores from water depths deeper than 3500 m. In contrast, 'Atlantic carbonate cycles' (low carbonate during glacials and high carbonate during interglacials) are observed in cores from depths shallower than 3000 m as a result of increased dilution of carbonate by terrigenous material during glacial low stands of sea level. Glacial-interglacial changes in the carbonate chemistry of South China Sea intermediate and deep waters resulted in significant changes in the positions of the carbonate compensation depth (CCD) and the aragonite compensation depth (ACD). During the last glacial the CCD and ACD were at least 400 and 1200 m deeper, respectively, than at present. Organic carbon accumulation rates in the South China Sea were approximately 2 times higher during the last glacial than the Holocene. Carbon isotopic analyses and C/N ratios of the organic matter indicate that only a small fraction of the increase in glacial organic carbon accumulation can be attributed to input of terrestrial carbon. On the basis of this we conclude that surface water productivity in the South China Sea was approximately 2 times higher during the last glacial maximum. This is consistent with previous studies which have demonstrated that glacial productivity was higher in low- to mid-latitude regions of the Atlantic and eastern Pacific. The deglacial decrease in organic carbon accumulation is accompanied by a decrease in delta13Corg. Using the relationship between delta13Corg and [CO2](aq) developed by Popp et al. [1989], we estimate that surface water pCO2 values in the South China Sea during the last 25,000 years were very similar to atmospheric CO2 concentrations.

Sedimentology, age models and stable isotope ratios of sediment cores from the equatorial Pacific

Based on detailed reconstructions of global distribution patterns, both paleoproductivity and the benthic d13C record of CO2, which is dissolved in the deep ocean, strongly differed between the Last Glacial Maximum and the Holocene. With the onset of Termination I about 15,000 years ago, the new (export) production of low- and mid-latitude upwelling cells started to decline by more than 2-4 Gt carbon/year. This reduction is regarded as a main factor leading to both the simultaneous rise in atmospheric CO2 as recorded in ice cores and, with a slight delay of more than 1000 years, to a large-scale gradual CO2 depletion of the deep ocean by about 650 Gt C. This estimate is based on an average increase in benthic d13C by 0.4-0.5 per mil. The decrease in new production also matches a clear 13C depletion of organic matter, possibly recording an end of extreme nutrient utilization in upwelling cells. As shown by Sarnthein et al., [1987], the productivity reversal appears to be triggered by a rapid reduction in the strength of meridional trades, which in turn was linked via a shrinking extent of sea ice to a massive increase in high-latitude insolation, i.e., to orbital forcing as primary cause.

25 Years of Polarstern Hydrography (1982-2007)

Since her commissioning in 1982 RV Polarstern has been operating in the Arctic and Antarctic to carry out scientific research. Between November and March she usually sails to and around the waters of the Antarctic, while the northern summer months are spent in Arctic waters. But also during transits between Bremerhaven and South Africa or South America long-term observations have regularly been performed by using a.o. XBT (Expendable Bathythermograph), CTD (Conductivity, Temperature, Depth), and Thermosalinograph which are standard instruments to carry out hydrographic measurements and are part of the standard instrumentation on board Polarstern. This report presents XBT and CTD profiles as well as sea surface temperature and salinity data recorded with Thermosalinograph during Polarstern cruises. In the framework of physical oceanographic studies the measurements were performed as part of international projects (e.g. like WOCE) or to support multidisciplinary studies.

Continuous 25-years aerosol records at coastal Antarctica: Part I. Variability and climate implications of ionic compounds

The aerosol climatology at the coastal Antarctic Neumayer Station (NM) was investigated based on continuous, 25-yr long observations of biogenic sulphur components (methanesulfonate and non-sea salt sulphate), sea salt and nitrate. Although significant long-term trends could only be detected for nitrate (-3.6 ± 2.5% per year between 1983 and 1993 and +4.0 ± 3.2% per year from 1993-2007), non-harmonic periodicities between 2 and 5 yr were typical for all species. Dedicated time series analyses revealed that relations to sea ice extent and various circulation indices are weak at best or not significant. In particular, no consistent link between sea ice extent and sea salt loadings was evident suggesting only a rather local relevance of the NM sea salt record. Nevertheless, a higher Southern Annular Mode index tended to entail a lower biogenic sulphur signal. In examining the spatial uniformity of the NM findings we contrasted them to respective 17 yr records from the coastal Dumont d'Urville Station. We found similar long-term trends for nitrate, indicating an Antarctic-wide but not identifiable atmospheric signal, although any significant impact of solar activity or pollution could be ruled out. No inter-site variability on the multiannual scale was evident for the other ionic compounds.

25 Years of Polarstern Meteorology

The most important tool in Germany's polar research program is the research and supply vessel Polarstern. The ship was commissioned in 1982, the maiden voyage started at the end of 1982. The owner of the ship is the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany. Within the last 25 years Polarstern performed a total of 44 expeditions to the Arctic and Antarctic. The ship is well equipped for meteorological research as well as for routine meteorological services. The meteorological office is permanently manned with a weather technician/- observer from the German Weather Service (DWD) who performs the routine 3-hourly synoptic observations and the daily upper air soundings. Additionally, a weather forecaster is responsible to advice the ships captain as well as the helicopter pilots and all scientists in any weather related question. The forecaster gets assistance from the weather technician who performs the satellite picture reception and manages the near real time data flow.

30 years of upper air soundings on board of R/V POLARSTERN (1982-12-29 to 2012-11-25)

The research vessel and supply icebreaker POLARSTERN is the flagship of the Alfred-Wegener-Institut in Bremerhaven (Germany) and one of the infrastructural pillars of German Antarctic research. Since its commissioning in 1982, POLARSTERN has conducted 30 campaigns to Antarctica (157 legs, mostly austral summer), and 29 to the Arctic (94 legs, northern summer). Usually, POLARSTERN is more than 300 days per year in operation and crosses the Atlantic Ocean in a meridional section twice a year. The first radiosonde on POLARSTERN was released on the 29th of December 1982, two days after POLARSTERN started on its maiden voyage to the Antarctic. And these daily soundings have continued up to the present. Due to the fact that POLARSTERN has reliably and regularly been providing upper air observations from data sparse regions (oceans and polar regions), the radiosonde data are of special value for researchers and weather forecast services alike. In the course of 30 years (1982-12-29 to 2012-11-25) a total of 12378 radiosonde balloons were started on POLARSTERN. All radiosonde data can now be found here. Each dataset contains the directly measured parameters air temperature, relative humidity and air pressure, and the derived altitude, wind direction and wind speed. 432 datasets additionally contain ozone measurements.