Isotope measurements from ODP Hole 104-642B

The Pliocene (5.3-2.6 Ma) is often described as a relatively stable climatic period, with warm temperatures characterizing high latitudes. New suborbital resolved stable isotope records from ODP Hole 642B in the Eastern Nordic Seas document that the Pliocene was not a stable period characterized by one climate. Rather, seven distinct climate phases, each lasting between 150,000 and 400,000 years, are identified and characterized in the time interval 5.1-3.1 Ma. Four of the transitions between the defined climate phases occurred close to an eccentricity minimum and a minimum in amplitude of change for Northern Hemisphere summer insolation, while two occurred around an eccentricity maximum and a maximum in amplitude in insolation change. Hence, a low frequency response of the Nordic Seas to insolation forcing is indicated. In addition, paleogeographic and related paleoceanographic changes, expansion of the Arctic sea ice cover and onset of NHG were important factors behind the evolving Pliocene low frequency variability in the eastern Nordic Seas. It is likely that the identified climate phases and transitions are important beyond the Nordic Seas, due to their association with changes to both insolation and paleogeography. Also, a strong and variable degree of diagenetic calcite overgrowth is documented for the planktic foraminifera, especially influencing the planktic d18O results; the absolute values and amplitude of change cannot be taken at face value.

Time series of air chemistry measurements at Georg-von-Neumayer station, Dronning Maud Land, Antarctica in the years 1982 to 1991

The first Air Chemistry Observatory at the German Antarctic station Georg von Neumayer (GvN) was operated for 10 years from 1982 to 1991. The focus of the established observational programme was on characterizing the physical properties and chemical composition of the aerosol, as well as on monitoring the changing trace gas composition of the background atmosphere, especially concerning greenhouse gases. The observatory was designed by the Institut für Umweltphysik, University of Heidelberg (UHEIIUP). The experiments were installed inside the bivouac lodge, mounted on a sledge and put upon a snow hill to prevent snow accumulation during blizzards. All experiments were under daily control and daily performance protocols were documented. A ventilated stainless steel inlet stack (total height about 3-4 m above the snow surface) with a 50% aerodynamic cut-off diameter around 7-10 µm at wind velocities between 4-10 m/s supplied all experiments with ambient air. Contamination free sampling was realized by several means: (i) The Air Chemistry Observatory was situated in a clean air area about 1500 m south of GvN. Due to the fact that northern wind directions are very rare, contamination from the base can be excluded for most of the time. (ii) The power supply (20 kW) is provided by a cable from the main station, thus no fuel-driven generator is operated in the very vicinity. (iii) Contamination-free sampling is controlled by the permanently recorded wind velocity, wind direction and by condensation particle concentration. Contamination was indicated if one of the following criteria were given: Wind direction within a 330°-30° sector, wind velocity <2.2 m/s or >17.5 m/s, or condensation particle concentrations >2500/cm**3 during summer, >800/cm**3 during spring/autumn and >400/cm**3 during winter. If one or a definable combination of these criteria were given, high volume aerosol sampling and part of the trace gas sampling were interrupted. Starting at 1982 through 1991-01-14 surface ozone was measured with an electrochemical concentration cell (ECC). Surface ozone mixing ratio are given in ppbv = parts per 10**9 by volume. The averaging time corresponds to the given time intervals in the data sheet. The accuracy of the values are better than ±1 ppbv and the detection limit is around 1.0 ppbv. Aerosols were sampled on two Whatman 541 cellulose filters in series and analyzed by ion chromatography at the UHEI-IUP. Generally, the sampling period was seven days but could be up to two weeks on occasion. The air flow was around 100 m**3/h and typically 10000-20000 m**3 of ambient air was forced through the filters for one sample. Concentration values are given in nanogram (ng) per 1 m**3 air at standard pressure and temperature (1013 mbar, 273.16 K). Uncertainties of the values were approximately ±10% to ±15% for the main components MSA, chloride, nitrate, sulfate and sodium, and between ±20% and ±30% for the minor species bromide, ammonium, potassium, magnesium and calcium.