Arctic Station Dirigibile Italia

BIOGENIC IODINE MEASUREMENTS IN SVALBARD SNOW (BIOMASS)

IADC_id: 146

active Call year: 2019

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The marine phytoplankton constitutes less than 1% of the global photosynthetic biomass however it is one of the major actors in the carbon cycle accounting for about 50% of global carbon fixation. In the same way of land plants, these microorganisms use chlorophyll to absorb the solar radiation and -through the photosynthesis- consume nutrients and CO2 releasing oxygen in the lower troposphere. Every year, the so called “biological carbon pump” is able to transfer worldwide about 10 gigatons of carbon from the atmosphere to the deep ocean regulating, ultimately, the global climate variability. In the Arctic region, the recent sea ice decline has progressively exposed a greater portion of oceanic surface that can be reached by sunlight resulting in an increase of marine phytoplankton productivity (MPP). In the last three decades in fact, according to satellite estimates of chlorophyll change, the increase of MPP has been of about 20%. Unfortunately, the satellite record covers only the last four decades, thus, in order to investigate the decadal to centennial MPP variability, high-resolution proxies in ice cores have been proposed. The most used are the Methanesulfonic acid (MSA) and Free Amino Acids (FAAs) (Barbaro et al., 2017). The disadvantage of the former is a limited period of stability within the snow layers (only few decades) while, up to this moment, there are no long record studies carried out with FAAs. In addition to the above mentioned, a new proxy based on iodine emission from sea-ice-associated phytoplankton and macro and micro algae is here proposed. During spring algal bloom in fact, the increase of chlorophyll concentration in the water has been observed to be accompanied also with an increase of tropospheric iodine species emission related the metabolism of marine organisms (Manley, 2002). The aim of the BIOMASS project is to collect multiple snow and ice samples to test the reliability of a new potential proxy (I_increse) for long-term MPP and sea ice reconstructions. This new proxy is based on the hypothesis that an increment of I/Na ratio in snow (normalized over sea water ratio) could reflect an increase of biogenic iodine (CH3I , CH2I2) emitted due to a change in ocean conditions (i.e. warmer SST). In particular, this study wants to investigate the sources, transport, deposition and stability of total iodine in Svalbard surface snow layer collected from early April to the end of May: a period encompassing reasonably the pre and post seasonal biological bloom that occurs in the surrounding shelf waters west of NyÅlesund. To achive this goal, a multiple snow sampling in the surrounding of the accessible Gruvebadet Observatory will be carried on for all the period indicated. Futhermore, two transects along the profile Kongsvegen and Holtedahlfonna glaciers will be necessary to investigate the geographical distribution of iodine deposition. Finally, a shallow core (15 m) from the Holtedahlfonna glacier will be drilled to compare the I/Na increment in ice with satellite measurements of chlorophyll-a in order to evaluate the applicability of this new proxy for paleoclimate studies. Complementary, back trajectory analyses will be used to define the sources and transport mechanisms of biogenic iodine and major ions.

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BIOGENIC IODINE MEASUREMENTS IN SVALBARD SNOW (BIOMASS)