An idealised wave-ice interaction model without subgrid spatial and temporal discretisations

A modified version of the wave-ice interaction model proposed by Williams et al (2013a,b) is presented for an idealised transect geometry. Wave attenuation due to ice floes and wave-induced ice fracture are both included in the wave-ice interaction model. Subgrid spatial and temporal discretisations are not required in the modified version of the model, thereby facilitating its future integration into large-scaled coupled models. Results produced by the new model are compared to results produced by the original model of Williams et al (2013b).Comment: 8 pages, 3 figure

Variability of sea ice area in the Bohai Sea from 1958 to 2015

With the backdrop of continuous global change, it is beneficial to create consistent long-term records of sea ice area on regional scales for ice disaster prevention and risk mitigation. In this study, a piecewise multiple nonlinear regression model was developed to reconstruct long-term daily sea ice area dataset in the Bohai Sea from 1958 to 2015 by linking the related meteorological data and the satellite-derived ice area. The validation analysis show that related meteorological status corresponding to physical process had stable skill of predictive ability, which was able to account for 81% of the observational variance under consideration of sea ice state, freezing and melting phases. The reconstructed daily sea ice area dataset was further used to study the interannual and seasonal variability of sea ice area. The annual maximum ice area (AMIA) and the annual average ice area (AAIA) in the Bohai Sea exhibited a decreasing trend with fluctuation of -0.33 +/- 0.18% yr(-1) and -0.51 +/- 0.16% yr(-1) over the period of 1958-2015, respectively. The most obvious change of the Bohai Sea ice area occurred in time scale of similar to 30 years. The whole study period could be divided into slight increasing stage (1958-1980), significant decreasing stage (1980-1995), and moderate increasing stage (1995-2015). In most years, the annual changes of sea ice area showed an unimodal variation and the freezing period (similar to 65 days) was longer than the melting phase (similar to 40 days) due to the relatively higher freezing rate. In addition, high correlations between AAIA and Arctic Oscillation (AO) index (r=-0.60, pPeer reviewe

Occurrence and mechanisms of extreme winter air temperatures in the Arctic and surrounding continents

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A means-corrected estimate for the Arctic sea-ice volume in 1990–2019

Decadal changes in sea-ice thickness are one of the most visible signs of climate variability and change. To gain a comprehensive understanding of mechanisms involved, long time series, preferably with good uncertainty estimates, are needed. Importantly, the development of accurate predictions of sea ice in the Arctic requires good observational products. To assist this, a new sea-ice thickness product by ESA Climate Change Initiative (CCI) is compared to a set of five ocean reanalysis (ECCO-V4r4, GLORYS12V1, ORAS5 and PIOMAS). The CCI product is based on two satellite altimetry missions, CryoSat-2 and ENVISAT, which are combined to the longest continuous satellite altimetry time series of Arctic-wide sea-ice thickness, 2002–2017. The CCI product performs well in the validation of the reanalyses: overall root-mean-square difference (RMSD) between monthly sea-ice thickness from CCI and the reanalyses ranges from 0.4–1.2 m. The differences are a sum of reanalysis biases, such as incorrect physics or forcing, as well as uncertainties in satellite altimetry, such as the snow climatology used in the thickness retrieval. The CCI and reanalysis basin-scale sea-ice volumes have a good match in terms of year-to-year variability and long-term trends but rather different monthly mean climatologies. These findings provide a rationale to construct a multi-decadal sea-ice volume time series for the Arctic Ocean and its sub-basins from 1990–2019 by adjusting the ocean reanalyses ensemble toward CCI observations. Such a time series, including its uncertainty estimate, provides new insights to the evolution of the Arctic sea-ice volume during the past 30 years.Peer reviewe

New Insights Into Cyclone Impacts on Sea Ice in the Atlantic Sector of the Arctic Ocean in Winter

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Atmospheric Circulation Response to Anomalous Siberian Forcing in October 2016 and its Long‐Range Predictability

Abstract: The warm Arctic-cold continent pattern was of record strength in October 2016, providing the opportunity to test its proposed influence on large-scale atmospheric circulation. We find a record weak polar stratospheric vortex and negative North Atlantic Oscillation in November-December 2016 and link them to increased planetary wave generation associated with cold Siberian anomalies followed by troposphere-stratosphere dynamical coupling. At the same time the warm Arctic anomalies, in particular those over the Barents-Kara Seas, do not appear to play an important role in forcing the atmospheric circulation. Long-range forecasts initialized on 1 October 2016 reproduced both the weak polar vortex and negative North Atlantic Oscillation, as well as their link with the Siberian temperatures. Our results support the stratospheric pathway for atmospheric circulation forcing associated with Siberian surface anomalies and uncover a source of skill for subseasonal forecasts from October to December. Plain Language Summary: The warm Arctic-cold continent pattern is an observed, large-scale pattern of near-surface temperatures where the Arctic is warmer than average and Siberia is colder than average. This pattern was of record strength in October 2016, providing the opportunity to test its influence on the Northern Hemisphere atmospheric circulation and the possibility of skillful long-range forecasts. It has been proposed that the warm Arctic-cold continent pattern can drive large atmospheric waves, which are able to travel from the troposphere into the stratosphere, where they weaken the strong wintertime winds that make up the stratospheric polar vortex. A weakened polar vortex can then lead to changes in the surface pressure that can affect weather patterns. We find a record weak polar stratospheric vortex in late autumn 2016 and link that to cold Siberian anomalies. At the same time the warm Arctic anomalies do not appear to play an important role in forcing the atmospheric circulation. Long-range forecasts initialized in October 2016 reproduced both the weak polar vortex and resulting surface pressure patterns. Our results support the stratospheric pathway for atmospheric circulation forcing by Siberian surface anomalies and uncover a source of skill for subseasonal forecasts in the Northern Hemisphere autumn.Peer reviewe

Links between Arctic sea ice and extreme summer precipitation in China: an alternative view

Potential links between the Arctic sea-ice concentration anomalies and extreme precipitation in China are explored. Associations behind these links can be explained by physical interpretations aided by visualisations of temporarily lagged composites of variables such as atmospheric mean sea level pressure and sea surface temperature. This relatively simple approach is verified by collectively examining already known links between the Arctic sea ice and rainfall in China. For example, similarities in the extreme summer rainfall response to Arctic sea-ice concentration anomalies either in winter (DJF) or in spring (MAM) are highlighted. Furthermore, new links between the Arctic sea ice and the extreme weather in India and Eurasia are proposed. The methodology developed in this study can be further applied to identify other remote impacts of the Arctic sea ice variability