Solar radiation over and under sea ice during the POLARSTERN cruise ARK-XXVI/3 (TransArc) in summer 2011

Arctic sea ice has declined and become thinner and younger (more seasonal) during the last decade. One consequence of this is that the surface energy budget of the Arctic Ocean is changing. While the role of surface albedo has been studied intensively, it is still widely unknown how much light penetrates through sea ice into the upper ocean, affecting sea-ice mass balance, ecosystems, and geochemical processes. Here we present the first large-scale under-ice light measurements, operating spectral radiometers on a remotely operated vehicle (ROV) under Arctic sea ice in summer. This data set is used to produce an Arctic-wide map of light distribution under summer sea ice. Our results show that transmittance through first-year ice (FYI, 0.11) was almost three times larger than through multi-year ice (MYI, 0.04), and that this is mostly caused by the larger melt-pond coverage of FYI (42 vs. 23%). Also energy absorption was 50% larger in FYI than in MYI. Thus, a continuation of the observed sea-ice changes will increase the amount of light penetrating into the Arctic Ocean, enhancing sea-ice melt and affecting sea-ice and upper-ocean ecosystems.

Magnetic properties of igneous rocks recovered at ODP Leg 127 sites

Measurements of natural remanent magnetization (NRM), initial susceptibility (K), anisotropy of magnetic susceptibility, frequency dependent susceptibility (Xfd), and viscous remanent magnetization (VRM) are reported from volcanic rocks recovered during ODP Leg 127 in the Japan Sea. The results indicate a significant difference between the basalts drilled in the Yamato Basin (Site 794 and 797) and in the Japan Basin (Site 795). The Koenigsberger ratios (Q) show very low values in the Yamato Basin attesting that the remanence is not dominant over the induced magnetization. This evidence could explain why no magnetic anomaly pattern has been recognized in this basin. Experiments of VRM acquisition and decay show that both the processes are multistage with the acquisition process proceeding more rapidly and deviates more from a log (t) law than the corresponding decay. The sediments interlayered with the basalts in the acoustic basement of the Yamato Basin show processes of remagnetization related to the emplacement of the dikes. Temperatures of heating between 200° and 250°C were estimated from the different unblocking temperatures of the two components of magnetization.

Sediment microstructures of ODP Leg 105 holes

Possible genetic relationships between syn- and post-depositional processes and sediment microstructure were investigated. Samples from cores at Sites 646 and 647 of Ocean Drilling Program (ODP) Leg 105 included examples of bottom current deposition (contourites), turbidity current deposition, consolidation, and diagenesis. Examination of nearly 200 micrographs of 14 samples from Site 646 and 13 samples from Site 647 leads to the conclusion that sedimentation processes do not appear to have an obvious influence on fabric. The effects of post-depositional processes, such as bioturbation, coring disturbance, and even remolding, appear to be less significant than one might expect as a result of the relatively coarse grain size of the sediments studied. Consolidation resulting from increased overburden stress results in increased particle alignment and compression of fabric elements with depth. The transition from open, random fabric in shallow samples to preferred orientation at depth represents the only change in these sediments that can be ascribed directly to a specific depositional or post-depositional process. Mineralogical variations, owing to changes in weathering processes and growth of authigenic/diagenetic minerals, also have a pronounced effect on sediment fabric.

Miocene pollen of ODP Leg 127 sites

Pollen floras were obtained from Miocene sediments recovered at four sites drilled during Ocean Drilling Program Leg 127. The local pollen floras of each site were correlated to the standard pollen zones of northeast Japan by using the concept of the essential members for each pollen zone. At Site 797, the complete floral range was obtained for recognition of the NP2 zone and the pollen components of the NP1 zone were also clarified continuously. The ages of the boundaries between pollen zones NP4/NP3, NP3/NP2, and NP2/NP1 are estimated to be about 7 Ma, 13 Ma, and 17-18.5 Ma, respectively. Even in the same pollen zone, the ratios of major pollen taxa vary with the location. This variation is expressed on maps representing two different times during the Miocene.