Horizontal profiles of longwave and shortwave radiation components over sea ice near Barrow, Alaska during the 2011 melt

An integrated instrument package for measuring and understanding the surface radiation budget of sea ice is presented, along with results from its first deployment. The setup simultaneously measures broadband fluxes of upwelling and downwelling terrestrial and solar radiation (four components separately), spectral fluxes of incident and reflected solar radiation, and supporting data such as air temperature and humidity, surface temperature, and location (GPS), in addition to photographing the sky and observed surface during each measurement. The instruments are mounted on a small sled, allowing measurements of the radiation budget to be made at many locations in the study area to see the effect of small-scale surface processes on the large-scale radiation budget. Such observations have many applications, from calibration and validation of remote sensing products to improving our understanding of surface processes that affect atmosphere-snow-ice interactions and drive feedbacks, ultimately leading to the potential to improve climate modelling of ice-covered regions of the ocean. The photographs, spectral data, and other observations allow for improved analysis of the broadband data. An example of this is shown by using the observations made during a partly cloudy day, which show erratic variations due to passing clouds, and creating a careful estimate of what the radiation budget along the observed line would have been under uniform sky conditions, clear or overcast. Other data from the setup's first deployment, in June 2011 on fast ice near Point Barrow, Alaska, are also shown; these illustrate the rapid changes of the radiation budget during a cold period that led to refreezing and new snow well into the melt season.

Age model for the time between 3.45 and 2.45 Ma of ODP Site 189-1172

Calcareous nannoplankton assemblages and benthic d18O isotopes of Pliocene deep-sea sediments of ODP site 1172 (East of Tasmania) have been studied to improve our knowledge of the Southern Ocean paleoceanography. Our study site is located just north of the Subtropical Front (STF), an ideal setting to monitor migrations of the STF during our study period, between 3.45 and 2.45 Ma. The assemblage identified at ODP site 1172 has been interpreted as characteristic for the transitional zone water mass, located south of the STF, based on: (i) the low abundances (< 1%) of subtropical taxa, (ii) relatively high percentages of Coccolithus pelagicus, a subpolar type species, (iii) abundances from 2-10% of Calcidiscus leptoporus, a species that frequently inhabits the zone south of the STF and (iv) the high abundances of small Noelaerhabdaceae which at present dominates the zone south of the STF. Across our interval the calcareous nannoplankton manifests glacial-interglacial variability. We have identified cold events, characterized by high abundances of C. pelagicus which coincide with glacial periods, except during G7. After 3.1 Ma cold events are more frequent, in concordance with global cooling trends. Around 2.75 Ma, the interglacial stage G7 is characterized by anomalous low temperatures which most likely are linked to definite closure of the Central American Seaway (CAS), an event that is believed to have had global consequences. A gradual increase of very small Reticulofenestra across our section marks a significant trend in the small Noelaerhabdaceae species group and has been linked to a general enhanced mixing of the water column in agreement with previous studies. It is suggested that a rapid decline of small Gephyrocapsa after isotopic stage G7 might be related to the cooling observed in our study site after the closure of the CAS.

Dinoflagellate abundance and events of ODP Site 189-1172 sediments

Palynomorphs were studied in samples from Ocean Drilling Program (ODP) Leg 189, Holes 1172A and 1172D (East Tasman Plateau; 2620 m water depth). Besides organic walled dinoflagellate cysts (dinocysts), broad categories of other palynomorphs were quantified in terms of relative abundance. In this contribution, we provide an overview of the dinocyst distribution from the Maastrichtian to lowermost Oligocene and Quaternary intervals and illustrate main trends in palynomorph distribution. The uppermost Cretaceous-lowermost Oligocene succession of Site 1172 has a confident biomagnetostratigraphy, enabling us to tie early Paleogene Southern Hemisphere dinocyst events to the geomagnetic polarity timescale for the first time. Dinocyst species from the Maastrichtian to earliest Oligocene at Site 1172 are largely endemic ("Transantarctic Flora") or bipolar; cosmopolitan taxa are present in the background as well. The Maastrichtian-early late Eocene dinocyst assemblages are indicative of shallow-marine to restricted marine, pro-deltaic conditions, closely tied to a massive siliciclastic sequence. By middle late Eocene times (~35.5 Ma), the siliciclastic sequence gave way to a thin glauconitic unit, considered to reflect the deepening of the Tasmanian Gateway. This transition coincides with the most prominent change in dinocyst associations of the Paleogene. The turnover is inferred to reflect a change from marginal marine to more offshore conditions, with increased winnowing and oxidation. Overlying pelagic carbonate ooze of middle early Oligocene and younger age is virtually barren of organic microfossils, although Quaternary assemblages have been recovered. This aspect is taken to reflect average low sedimentation rates and well-oxygenated water masses during most of the Oligocene and Neogene. The few palynologically productive samples from the Oligocene-Quaternary interval have a stronger cosmopolitan to subtropical signature, with warm-water species being common to abundant.