Ice rafted debris and reconstructed sea surface temperature of ODP Hole 104-642B

The mid-Piacenzian warm period (3.264-3.025 Ma) of the Pliocene epoch has been proposed as a possible reference for future warm climate states. However, there is significant disagreement over the magnitude of high latitude warming between data and models for this period of time, raising questions about the driving mechanisms and responsible feedbacks. We have developed a new set of orbital-resolution alkenone-based sea surface temperature (SST) and ice rafted debris (IRD) records from the Norwegian Sea spanning 3.264-3.14 Ma. The SSTs in the Norwegian Sea were 2-3?°C warmer than the Holocene average, likely caused by the radiative effect of higher atmospheric CO2 concentrations. There is notable obliquity-driven SST variability with a range of 4?°C, shown by evolutive spectra. The correlation of SST variability with the presence of IRD suggests a common climate forcing acting across the Nordic Seas region. Changes of the SST gradient between the Norwegian Sea and North Atlantic sites suggest that the subpolar gyre was at least as strong as during the Holocene, and that the northward heat transport by the North Atlantic Current was comparable.

Space-time Reconstruction of Oceanic Sea States via Variational Stereo Methods

We present a remote sensing observational method for the measurement of the spatio-temporal dynamics of ocean waves. Variational techniques are used to recover a coherent space-time reconstruction of oceanic sea states given stereo video imagery. The stereoscopic reconstruction problem is expressed in a variational optimization framework. There, we design an energy functional whose minimizer is the desired temporal sequence of wave heights. The functional combines photometric observations as well as spatial and temporal regularizers. A nested iterative scheme is devised to numerically solve, via 3-D multigrid methods, the system of partial differential equations resulting from the optimality condition of the energy functional. The output of our method is the coherent, simultaneous estimation of the wave surface height and radiance at multiple snapshots. We demonstrate our algorithm on real data collected off-shore. Statistical and spectral analysis are performed. Comparison with respect to an existing sequential method is analyzed.