Abstract
The Arctic sea-ice extent has strongly declined over recent decades. A large inter-annual variability is superimposed on this negative trend. Previous studies have emphasised a significant warming effect associated with latent energy transport into the Arctic region, in particular due to an enhanced greenhouse effect associated with the convergence of the humidity transport over the Arctic. The atmospheric energy transport into the Arctic is mostly accomplished by waves such as Rossby waves and cyclones. Here we present a systematic study of the effect on Arctic sea ice of these atmospheric wave types. Through a regression analysis we investigate the coupling between transport anomalies of both latent and dry-static energy and sea-ice anomalies. From the state-of-the-art ERA5 reanalysis product the latent and dry-static transport over the Arctic boundary (70^{circ } N) is calculated. The transport is then split into transport by planetary and synoptic-scale waves using a Fourier decomposition. The results show that latent energy transport as compared to that of dry-static shows a much stronger potential to decrease sea ice concentration. However, taking into account that the variability of dry-static transport is of an order of magnitude larger than latent, the actual impact on the sea ice appears similar for the two components. In addition, the energy transport by planetary waves causes a strong decline of the sea ice concentration whereas the transport by synoptic-scale waves shows only little effect on the sea ice. The study emphasises the importance of the large-scale waves on the sea ice variability.
Highlights
The fast decrease in Arctic sea ice extent is one of the clearest indicators of the ongoing global warming due to anthropogenic greenhouse gas emissions (Fox-Kemper et al 2021)
3.1 Impact of planetary and synoptic transport on Arctic sea ice Atmospheric energy-transport by planetary waves leads to a decrease in Arctic sea-ice concentration (SIC)
In this study we show the impact of latent as well as drystatic atmospheric energy transport on the Arctic sea ice cover
Summary
The fast decrease in Arctic sea ice extent is one of the clearest indicators of the ongoing global warming due to anthropogenic greenhouse gas emissions (Fox-Kemper et al 2021). Passive microwave satellite records from 1978 and onwards show significant trends of a decreasing sea-ice extent for every month of the year, with September showing the strongest decrease (Serreze and Stroeve 2015). Several processes and mechanisms have been suggested to be important for the sea-ice variability, such as those induced by radiative effects related to surface albedo (Kashiwase et al 2017), low-level clouds (Kay et al 2008; Kay and L’Ecuyer 2013; Liu and Schweiger 2017), surface winds (Ogi et al 2010; Zhang et al 2013; Mills and Walsh 2014), and oceanic (Årthun et al 2012) and atmospheric (Kapsch et al 2013; Park et al 2015; Woods and Caballero 2016; Wang et al 2020) energy transport. Previous studies have shown impact of atmospheric heat and moisture transport variability on the Arctic surface temperatures (Graversen 2006; Woods et al 2013; Baggett et al 2016), and that e.g. cloud, humidity, and surface albedo are modified by this transport (Graversen and Burtu 2016; Liu and Schweiger 2017; Graversen and Langen 2019)
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