ALBERT

Description: We measured aerosol size distributions and conducted bulk as well as size segregated aerosol sampling during two summer campaigns in January 2015 and January 2016 at the continental Antarctic station Kohnen (Dronning Maud Land). Physical and chemical aerosol properties differ conspicuously during the episodic impact of an outstanding low pressure system in 2015 (LPS15) compared to the prevailing clear sky conditions (CSC): The about three days persisting LPS15, located in the eastern Weddell Sea, was associated with marine boundary layer (MBL) air mass intrusion, enhanced condensation particle concentrations (1400±700 cm-3 compared to 250±120 cm-3 during CSC; mean ± SD), occurrence of a new particle formation (NPF) event exhibiting a continuous growth of particle diameters (Dp) from 12 nm to 43 nm over 44 hours (growth rate 0.6 nm h-1), peaking methane sulfonate (MS-), non-sea salt sulfate (nss-SO42-) and Na+ concentrations (190 ng m-3 MS-, 137 ng m-3 nss-SO42-, and 53 ng m-3 Na+ compared to 24±15 ng m-3, 107±20 ng m-3 and 4.1±2.2 ng m-3, respectively, during CSC), and finally an increased MS-/nss-SO42- mass ratio ßMS of 0.4 up to 2.3 (0.21±0.1 during CSC) comparable to typical values found at coastal Antarctic sites. Throughout the observation period a larger part of MS- could be found in super micron aerosol compared to nss-SO42-, i.e. (10±2) % by mass compared to (3.2±2) %, respectively. On the whole, during CSC aged aerosol characterized by an usually mono-modal size distribution around Dp = 60 nm was observed. Although our observations indicate that sporadic impacts of coastal cyclones were associated with enhanced marine aerosol entry, at large aerosol deposition on-site during austral summer should be dominated by the typical steady CSC.

Description: A new 21.3m firn core was drilled in 2015 at a coastal Antarctic high accumulation site in Adélie Land (66.78°S; 139.56°E, 602ma.s.l.). The core was dated by annual layers counting based on non-sea-salt sulfate and methanesulfonate summer peaks, refined by a comparison between the reconstructed surface mass balance (hereafter, SMB) and the closest available stake data. The mean reconstructed SMB of 75.2 ± 15.0cmw.e. y−1 is consistent with local stake data, and remarkably high for coastal East Antarctica. The resulting inter-annual and sub-annual variations in isotopic records (δ18O and deuterium excess, hereafter d-excess) are explored for 1998–2014 and are systematically compared with a couple of climatic time series: an updated database of Antarctic surface snow isotopic composition, SMB stake data, meteorological observations from Dumont d'Urville station, sea-ice concentration based on passive microwave satellite data, precipitation outputs of atmospheric reanalyses, climate and water stable isotope outputs from the atmospheric general circulation model ECHAM5-wiso, as well as air mass origins diagnosed using 5-days back-trajectories. The mean isotopic values (−19.3 ± 3.1‰ for δ18O and 5.4 ± 2.2‰ for d-excess) are consistent with other coastal Antarctic values. No significant isotope-temperature relationship can be evidenced at any timescale, ruling out a simple interpretation of in terms of local temperature. An observed asymmetry in the δ18O seasonal cycle may be explained by the precipitation of air masses coming from Indian and Pacific/West Antarctic Ice Sheet sectors in autumn and winter times, recorded in the d-excess signal showing outstanding values in austral spring versus autumn. Significant positive trends are observed in the annual d-excess record and local sea-ice extent (135°E–145°E) over the period 1998–2014. However, processes studies focusing on resulting isotopic compositions and particularly the d-excess-δ18O relationship, evidenced as a potential fingerprint of moisture origins, as well as the collection of more isotopic measurements in Adélie Land are needed for an accurate interpretation of our signals.

Description: The Mediterranean Sea hydrology at the time of the Heinrich formation in the North Atlantic Ocean was analyzed by comparing sea surface temperatures (SSTs) and oxygen isotope composition of seawater (dw) changes during the past 75 kyr in two marine cores. These were compared to the palynological variations derived in the Mediterranean Sea core. During the last glacial the two oceanic SST records show similar and synchronous patterns, with several long-term cooling periods, ending by abrupt SST increases. At the time of the Heinrich events, cold SSTs and low salinity prevailed in the Mediterranean Sea. The freshwater budget was similar to the modern one, permitting the presence of a mixed forest on the Mediterranean borderlands. The post-Heinrich periods are marked by a freshwater budget decrease, limiting oak and fir tree growth in the Mediterranean region. Increase of precipitation or reduction of evaporation is observed before the Heinrich episode, and is associated with a well-developed mixed Mediterranean forest.