![]() ![]() ![]() Rising air and ocean temperatures have enhanced summer MYI melt while thermodynamic growth in winter has remained slow, leading to a decrease of 50% in the MYI fraction ( Kwok, 2018 Stroeve and Notz, 2018, and references therein). Because thermodynamics and dynamics shape the ITD differently, this study used ITDs to distinguish them (e.g., Thorndike et al., 1975 Haas et al., 2008).ĭriven by thermodynamics, the large losses of thick, multi-year ice (MYI) increase the seasonality, i.e., the annual differences, in the Arctic sea ice mass balance ( Kwok, 2018). The large range of ice thicknesses can be summarized in an ice thickness distribution (ITD), i.e., a histogram of all occurring ice thicknesses ( Thorndike et al., 1975). Thick ridges change the air and ocean drag, provide shelter for biota, and increase the likelihood of the sea ice surviving the summer melt (e.g., Castellani et al., 2014 Fernández-Méndez et al., 2018). For example, the ocean-atmosphere heat and moisture fluxes are limited by thin ice (e.g., Maykut, 1978). As most air-sea interactions and biogeochemical processes are sensitive to only a fraction of the thickness range, e.g., the very thin ice or the thick ridges, knowledge of the relative coverage of different ice thicknesses is crucial for the parameterization of important climate processes ( Holland et al., 2006 Lipscomb et al., 2007 Notz, 2009). Dynamics create an icescape with heterogeneous ice thicknesses ranging from a few centimeters to several meters ( Wadhams, 2000). The complex interaction between thermodynamics and dynamics shapes the ice thickness distribution throughout the life cycle of the Arctic sea ice cover. Colliding floes form pressure ridges or rafts, and floes breaking apart from each other create leads, where new ice can form. ![]() In addition, sea ice dynamics alter the ice thickness through sea ice deformation. The difference in air temperature and solar radiation between polar night and day induces a strong, thermodynamic seasonal cycle in the mean ice thickness, which is amplified or damped by internal feedbacks ( Wadhams, 2000 Massonnet et al., 2018). Our comprehensive description of seasonal changes of the sea ice thickness distribution is valuable for interpreting MOSAiC time series across disciplines and can be used as a reference to advance sea ice thickness modeling.Īrctic sea ice is thinning at a rate of about 10% per decade, and its seasonal variability is increasing (e.g., Kwok, 2018 Massonnet et al., 2018 Stroeve and Notz, 2018). We demonstrate that this Lagrangian sea ice thickness data set is well suited for validating the existing redistribution theory in sea ice models. We suggest that the large dynamic thickening was due to the mobile, unconsolidated sea ice pack and periodic, sub-daily motion. One unexpected outcome was the large dynamic thickening in a regime where divergence prevailed on average in the western Nansen Basin in spring. The spatial differences in mean sea ice thickness between the Central Observatory (<10 km) of MOSAiC and the Distributed Network (<50 km) were negligible in fall and only 0.2 m in late winter, but the relative abundance of thin and thick ice varied. The airborne EM measurements bridged the scales from local floe-scale measurements to Arctic-wide satellite observations and model grid cells. These processes caused a 1-month delay between maximum thermodynamic sea ice thickness and maximum mean ice thickness. Ice dynamics and deformation-related processes, such as thin ice formation in leads and subsequent ridging, broadened the ice thickness distribution and contributed 30% to the increase in mean thickness. We found that thermodynamic growth and decay dominated the seasonal cycle with a total mean sea ice thickness increase of 1.4 m (October 2019 to June 2020) and decay of 1.2 m (June 2020 to September 2020). Data from ice mass balance and position buoys provided additional information. We analyzed 11 large-scale (∼50 km) airborne electromagnetic sea thickness and surface roughness surveys from October 2019 to September 2020. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition provided a unique opportunity to study seasonal sea ice thickness changes of the same sea ice. Thermodynamic and dynamic processes alter the sea ice thickness. Sea ice thickness is a key parameter in the polar climate and ecosystem. ![]()
0 Comments
Leave a Reply. |