Ar and U-Th-Pb age determinations for minerals from ODP Holes of ODP Legs 173 and 210

We report U-Pb and 39Ar-40Ar measurements on plutonic rocks recovered from the Ocean Drilling Program (ODP) Legs 173 and 210. Drilling revealed continental crust (Sites 1067 and 1069) and exhumed mantle (Sites 1070 and 1068) along the Iberia margin and exhumed mantle (Site 1277) on the conjugate Newfoundland margin. Our data record a complex igneous and thermal history related to the transition from rifting to seafloor spreading. The results show that the rift-to-drift transition is marked by a stuttering start of MORB-type magmatic activity. Subsequent to initial alkaline magmatism, localized mid-oceanic ridge basalts (MORB) magmatism was again replaced by basin-wide alkaline events, caused by a low degree of decompression melting due to tectonic delocalization of deformation. Such "off-axis" magmatism might be a common process in (ultra-) slow oceanic spreading systems, where "magmatic" and "tectonic" spreading varies in both space and time.

Radiolarians of the Celebes Sea

Two sites were drilled in the Celebes Sea as part of Ocean Drilling Program Leg 124; Site 767 and Site 770. Radiolarians are preserved in Paleogene pelagic claystones with minor occurrences in certain Neogene successions. The brown clays that immediately overlie basalt at both sites contain radiolarians of the late middle Eocene Podocyrtis chalara Zone. Late Eocene radiolarians are not found, due to dissolution and probable hiatus. The Oligocene is represented by the Theocyrtis tuberosa and Dorcadospyris ateuchus Zones. Oligocene sediments are strongly dominated by abundant and diverse radiolarians of the TristylospyrislDorcadospyris lineage. Preservation of Paleogene radiolarian assemblages ranges from good to very poor. Late Miocene radiolarians of the Didymocyrtis antepenultima Zone are found only in Site 770. Other Neogene sediments are barren of radiolarian remains, with the exception of latest Pleistocene and Holocene sediments.

High resolved snow height measurements at Neumayer Station, Antarctica, 2013

Antarctica is a continent with a strong character. High wind speeds, very low temperatures and heavy snow storms. All these parameters are well known due to observations and measurements, but precipitation measurements are still rare because the number of manned stations is very limited in Antarctica. In such a polar snow region many wind driven phenomena associated with snow fall exist like snow drift, blowing snow or sastrugi. Snow drift is defined as a layer of snow formed by the wind during a snowstorm. The horizontal visibility is below eye level. Blowing snow is specified as an ensemble of snow particles raised by the wind to moderate or great heights above the ground; the horizontal visibility at eye level is generally very poor (National Snow And Ice Data Center (NSIDC), 2013). Sastrugi are complex, fragile and sharp ridges or grooves formed on land or over sea ice. They arise from wind erosion, saltation of snow particles and deposition. To get more details about these procedures better instruments than the conventional stake array are required. This small report introduces a new measuring technique and therefore offers a never used dataset of snow heights. It is very common to measure the snow height with a stake array in Antarctica (f.e. Neumayer Station, Kohnen Station) but not with a laser beam. Thus the idea was born to install a new instrument in December 2012 at Neumayer Station.

Sea urchin response to rising pCO2 shows ocean acidification may fundamentally alter the chemistry of marine skeletons

Ocean acidification caused by an increase in pCO2 is expected to drastically affect marine ecosystem composition, yet there is much uncertainty about the mechanisms through which ecosystems may be affected. Here we studied sea urchins that are common and important grazers in the Mediterranean (Paracentrotus lividus and Arbacia lixula). Our study included a natural CO2 seep plus reference sites in the Aegean Sea off Greece. The distribution of A. lixula was unaffected by the low pH environment, whereas densities of P. lividus were much reduced. There was skeletal degradation in both species living in acidified waters compared to reference sites and remarkable increases in skeletal manganese levels (P. lividus had a 541% increase, A. lixula a 243% increase), presumably due to changes in mineral crystalline structure. Levels of strontium and zinc were also altered. It is not yet known whether such dramatic changes in skeletal chemistry will affect coastal systems but our study reveals a mechanism that may alter inter-species interactions.

(Supplementary Table 1) Mercury isotope values for common and thick-billed murre (Uria aalge, Uria lomvia) eggs from Alaska

Atmospheric deposition of mercury to remote areas has increased threefold since pre-industrial times. Mercury deposition is particularly pronounced in the Arctic. Following deposition to surface oceans and sea ice, mercury can be converted into methylmercury, a biologically accessible form of the toxin, which biomagnifies along the marine food chain. Mass-independent fractionation of mercury isotopes accompanies the photochemical breakdown of methylmercury to less bioavailable forms in surface waters. Here we examine the isotopic composition of mercury in seabird eggs collected from colonies in the North Pacific Ocean, the Bering Sea and the western Arctic Ocean, to determine geographical variations in methylmercury breakdown at northern latitudes. We find evidence for mass-independent fractionation of mercury isotopes. The degree of mass-independent fractionation declines with latitude. Foraging behaviour and geographic variations in mercury sources and solar radiation fluxes were unable to explain the latitudinal gradient. However, mass-independent fractionation was negatively correlated with sea-ice cover. We conclude that sea-ice cover impedes the photochemical breakdown of methylmercury in surface waters, and suggest that further loss of Arctic sea ice this century will accelerate sunlight-induced breakdown of methylmercury in northern surface waters.