Table 2: Firn temperature, ram resistance, mass balance and submergence velo city measurements on Colle Gnifetti

Distributional patterns of glaciological parameters at the Colle Gnifetti core drilling site are described and their interrelationships are brietly discussed. Observations within a stake network established in 1980 furnish information about snow accumulation (short term balance), submergence velocity of ice tlow (long term balance), ram hardness (melt layer stratigraphy), and firn temperature. In addition, a numerical model was used to estimate local variations of available radiant energy. Melt layer formation is considerably more intensive on the south facing parts of the firn saddie where incoming radiation is high. These melt layers seem to effectively protect some of the fallen snow from wind erosion. As a result, balance ist up to one order of magnitude larger on south facing slopes. Heat applied to the surface is therefore positively correlated with balance, whereas the relation between solar radiation and firn temperature is less dear. Distributional patterns of submergence velocity confirm that the observed spatial variability of surface balance is representative for longer time periods and greatly intluences the time scale and the stratigraphy of firn and ice cores from Colle Gnifetti.

Total organic carbon (TOC) on ground bulk and carbonate-free sediment samples of ODP Hole 151-911A

A multiproxy analysis of Hole 911A (Ocean Drilling Program (ODP) Leg 151) drilled on the Yermak Plateau (eastern Arctic Ocean) is used to investigate the behaviour of the Svalbard/Barents Sea ice sheet (SBIS) during late Pliocene and early Pleistocene (~3.0-1.7 Ma) climate changes. Contemporary with the 'Mid-Pliocene (~3 Ma) global warmth' (MPGW), a warmer period lasting ~300 kyr with seasonally ice-free conditions in the marginal eastern Arctic Ocean is assumed to be an important regional moisture source, and possibly one decisive trigger for intensification of the Northern Hemisphere glaciation in the Svalbard/Barents Sea area at ~2.7 Ma. An abrupt pulse of ice-rafted debris (IRD) to the Yermak Plateau at ~2.7 Ma reflects distinct melting of sediment-laden icebergs derived from the SBIS and may indicate the protruding advance of the ice sheet onto the outer shelf. Spectral analysis of the total organic carbon (TOC) record being predominantly of terrigenous/fossil-reworked origin indicates SBIS and possibly Scandinavian Ice Sheet response to incoming solar radiation at obliquity and precession periodicities. The strong variance in frequencies near the 41 kyr obliquity cycle between 2.7 and 1.7 Ma indicates, for the first time in the Arctic Ocean, a close relationship of SBIS growth and decay patterns to the Earth's orbital obliquity amplitudes, which dominated global ice volume variations during late Pliocene/early Pleistocene climate changes.

Rising CO2 and increased light exposure synergistically reduce marine primary productivity

Carbon dioxide and light are two major prerequisites of photosynthesis. Rising CO2 levels in oceanic surface waters in combination with ample light supply are therefore often considered stimulatory to marine primary production. Here we show that the combination of an increase in both CO2 and light exposure negatively impacts photosynthesis and growth of marine primary producers. When exposed to CO2 concentrations projected for the end of this century, natural phytoplankton assemblages of the South China Sea responded with decreased primary production and increased light stress at light intensities representative of the upper surface layer. The phytoplankton community shifted away from diatoms, the dominant phytoplankton group during our field campaigns. To examine the underlying mechanisms of the observed responses, we grew diatoms at different CO2 concentrations and under varying levels (5-100%) of solar radiation experienced by the phytoplankton at different depths of the euphotic zone. Above 22-36% of incident surface irradiance, growth rates in the high-CO2-grown cells were inversely related to light levels and exhibited reduced thresholds at which light becomes inhibitory. Future shoaling of upper-mixed-layer depths will expose phytoplankton to increased mean light intensities. In combination with rising CO2 levels, this may cause a widespread decline in marine primary production and a community shift away from diatoms, the main algal group that supports higher trophic levels and carbon export in the ocean.

Climate variability in the Aegean Sea (marine record M2, Athos basin) during the past 1500 years

We provide new evidence on sea surface temperature (SST) variations and paleoceanographic/paleoenvironmental changes over the past 1500 years for the north Aegean Sea (NE Mediterranean). The reconstructions are based on multiproxy analyses, obtained from the high resolution (decadal to multi-decadal) marine record M2 retrieved from the Athos basin. Reconstructed SSTs show an increase from ca. 850 to 950 AD and from ca. 1100 to 1300 AD. A cooling phase of almost 1.5 °C is observed from ca. 1600 AD to 1700 AD. This seems to have been the starting point of a continuous SST warming trend until the end of the reconstructed period, interrupted by two prominent cooling events at 1832 ± 15 AD and 1995 ± 1 AD. Application of an adaptive Kernel smoothing suggests that the current warming in the reconstructed SSTs of the north Aegean might be unprecedented in the context of the past 1500 years. Internal variability in atmospheric/oceanic circulations systems as well as external forcing as solar radiation and volcanic activity could have affected temperature variations in the north Aegean Sea over the past 1500 years. The marked temperature drop of approximately ~2 °C at 1832 ± 15 yr AD could be related to the 1809 ?D 'unknown' and the 1815 AD Tambora volcanic eruptions. Paleoenvironmental proxy-indices of the M2 record show enhanced riverine/continental inputs in the northern Aegean after ca. 1450 AD. The paleoclimatic evidence derived from the M2 record is combined with a socio-environmental study of the history of the north Aegean region. We show that the cultivation of temperature-sensitive crops, i.e. walnut, vine and olive, co-occurred with stable and warmer temperatures, while its end coincided with a significant episode of cooler temperatures. Periods of agricultural growth in Macedonia coincide with periods of warmer and more stable SSTs, but further exploration is required in order to identify the causal links behind the observed phenomena. The Black Death likely caused major changes in agricultural activity in the north Aegean region, as reflected in the pollen data from land sites of Macedonia and the M2 proxy-reconstructions. Finally, we conclude that the early modern peaks in mountain vegetation in the Rhodope and Macedonia highlands, visible also in the M2 record, were very likely climate-driven.

Thermal measurements on sub-Antarctic megaherbs and environmental characteristics on Campbell Island in 2010

We evaluated whether heating occurs in sub-Antarctic megaherbs, and the relation of heating to relevant environmental variables. We measured leaf and inflorescence temperature in six sub-Antarctic megaherb species on Campbell Island, latitude 52.3°S, New Zealand Biological Region. Using thermal imaging camera (Fluke TI20, http://www.fluke.com/fluke/caen/support/software/ti-update) and thermal probe (Fluke 51 II digital thermal probe), in combination with measurement of solar radiation, ambient air temperature, wind speed, wind chill and humidity.

Seawater carbonate chemistry, pigments and biological processes during experiments with coralline alga Corallina sessilis

Previous studies have shown that increasing atmospheric CO2 concentrations affect calcification in some planktonic and macroalgal calcifiers due to the changed carbonate chemistry of seawater. However, little is known regarding how calcifying algae respond to solar UV radiation (UVR, UVA+UVB, 280-400 nm). UVR may act synergistically, antagonistically or independently with ocean acidification (high CO2/low pH of seawater) to affect their calcification processes. We cultured the articulated coralline alga Corallina sessilis Yendo at 380 ppmv (low) and 1000 ppmv (high) CO2 levels while exposing the alga to solar radiation treatments with or without UVR. The presence of UVR inhibited the growth, photosynthetic O2evolution and calcification rates by13%, 6% and 3% in the low and by 47%, 20% and 8% in the high CO2 concentrations, respectively, reflecting a synergistic effect of CO2 enrichment with UVR. UVR induced significant decline of pH in the CO2-enriched cultures. The contents of key photosynthetic pigments, chlorophyll a and phycobiliproteins decreased, while UV-absorptivity increased under the highpCO2/low pH condition. Nevertheless, UV-induced inhibition of photosynthesis increased when the ratio of particulate inorganic carbon/particulate organic carbon decreased under the influence of CO2-acidified seawater, suggesting that the calcified layer played a UV-protective role. Both UVA and UVB negatively impacted photosynthesis and calcification, but the inhibition caused by UVB was about 2.5-2.6 times that caused by UVA. The results imply that coralline algae suffer from more damage caused by UVB as they calcify less and less with progressing ocean acidification.

Geochemistry of sediment cores GeoB4901-3 and GeoB4901-8 from the southern flank of the Niger Fan

Time series of terrigenous source elements (Al, K, Ti, Zr) from core GeoB4901-8 recovered from the deep-sea fan of the Niger River record variations in riverine sediment discharge over the past 245,000 yr. Although the flux rates of all the elements depend on physical erosion, which is mainly controlled by the extent of vegetation coverage in central Africa, element/Al ratios reflect conditions for chemical weathering in the river basin. Maximum sediment input to the ocean occurs during cold and arid periods, when precipitation intensity and associated freshwater runoff are reduced. High carbonate contents during the same periods indicate that the sediment supply has a positive effect on river-induced marine productivity. In general, variations in the terrestrial signals contain a strong precessional component in tune with changes in low-latitude solar radiation. However, the terrestrial signal lags the insolation signal by several thousand years. K/Al, Ti/Al, and Zr/Al records reveal that African monsoonal precipitation depends on high-latitude forcing. We attribute the shift between insolation cycle and river discharge to the frequently reported nonlinear response of African climate to primary orbital configurations, which may be caused by a complex interaction of the secondary control parameters, such as surface albedo and/or thermohaline circulation.