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Bashmachnikov, I. L., Fedorov, A. M., Vesman, A. V., Belonenko, T. V., & Dukhovskoy, D. S. (2019). Thermohaline convection in the subpolar seas of the North Atlantic from satellite and in situ observations. Part 2: indices of intensity of deep convection.16(1), 191–201.
Abstract: Variation in locations of the maximum development of deep convection in the subpolar seas, taking into account their small dimensions, represent difficulty in identifying its interannual variability from usually sparse in situ data. In this work, the interannual variability of the maximum convection depth, is obtained using one of the most complete datasets ARMOR, which combines in situ and satellite data. The convection depths, derived from ARMOR, are used for testing the efficiency of two indices of convection intensity: (1) sea-level anomalies from satellite altimetry and (2) the integral water density in the areas of the most frequent development of deep convection. The first index, capturing some details, shows low correlations with the interannual variability of the deep convection intensity. The second index shows high correlation with the deep convection intensity in the Greenland, Irminger and Labrador seas. Asynchronous variations in the deep convection intensity in the Labrador-Irminger seas and in the Greenland Sea are obtained. In the Labrador and in the Irminger seas, the quasi-seven-year variations in the convection intensity are identified.
Keywords: deep convection, assimilation of satellite data, altimetry, water density, the Greenland Sea, the Labrador Sea, the Irminger Sea
Dukhovskoy, D. S., Yashayaev, I., Proshutinsky, A., Bamber, J. L., Bashmachnikov, I. L., Chassignet, E. P., et al. (2019). Role of Greenland Freshwater Anomaly in the Recent Freshening of the Subpolar North Atlantic. J. Geophys. Res. Oceans, 124(5), 3333–3360.
Abstract: The cumulative Greenland freshwater flux anomaly has exceeded 5000 km3 since the 1990s. The volume of this surplus fresh water is expected to cause substantial freshening in the North Atlantic. Analysis of hydrographic observations in the subpolar seas reveal freshening signals in the 2010s. The sources of this freshening are yet to be determined. In this study, the relationship between the surplus Greenland freshwater flux and this freshening is tested by analyzing the propagation of the Greenland freshwater anomaly and its impact on salinity in the subpolar North Atlantic based on observational data and numerical experiments with and without the Greenland runoff. A passive tracer is continuously released during the simulations at freshwater sources along the coast of Greenland to track the Greenland freshwater anomaly. Tracer budget analysis shows that 44% of the volume of the Greenland freshwater anomaly is retained in the subpolar North Atlantic by the end of the simulation. This volume is sufficient to cause strong freshening in the subpolar seas if it stays in the upper 50�100 m. However, in the model the anomaly is mixed down to several hundred meters of the water column resulting in smaller magnitudes of freshening compared to the observations. Therefore, the simulations suggest that the accelerated Greenland melting would not be sufficient to cause the observed freshening in the subpolar seas and other sources of fresh water have contributed to the freshening. Impacts on salinity in the subpolar seas of the freshwater transport through Fram Strait and precipitation are discussed.
Keywords: Greenland ice sheet melting; freshwater anomaly; subpolar North Atlantic; subpolar gyre; passive tracer numerical experiment; freshwater budget