The Influence of Arctic Landfast Ice on Seasonal Modulation of the M₂ Tide

Abstract

Arctic sea ice is subject to large seasonal variations in extent, thickness and mobility. Most of the Arctic region is covered by sea ice in winter months, with a total area of ∼15 million km 2 ; however, this area declines by a factor of 3 to ∼4.5 million km 2 , by summer (average 2011-2019 National Snow and Ice Data Center, 2020). Moreover, in winter there is about 1.65 million km 2 of landfast sea ice, that reduces to near zero in summer (Li et al., 2020). The presence of landfast ice can significantly affect local hydrodynamics as it prevents interaction between the atmosphere and underlying ocean (Mahoney et al., 2014).While an ice cover shields the ocean from atmospheric forcing, it also exerts additional frictional stress on the surface. Early studies demonstrate that drag between water and ice results in tidal dampening, especially in coastal zones where ice is relatively immobile (Godin, 1986;Kowalik, 1981). Kowalik (1981) showed that the presence of sea ice can lead to tidal amplitude decay and phase delay. More recent studies have looked specifically into the modulation of tides in the Arctic region in response to a seasonally varying ice cover and suggest the effect to be substantial; in some regions changing the amplitude by up to 0.15 m (Kagan & Sofina, 2010;St-Laurent et al., 2008). This implies that it is insufficient to regard tides as constant throughout the year and ignore the influence of sea ice, which is done in most operational tide models. For accurate prediction of Arctic tidal water levels, quantification of seasonal modulation is necessary. In addition, studies have shown that Arctic tides directly affect North Atlantic tides (Arbic et al., 2004(Arbic et al., , 2007,

Secular Trends in Global Tides Derived From Satellite Radar Altimetry

“…On the other hand, part of the observed signal could be related to sea ice decline (see e.g., Haigh et al, 2020). Namely, the observed changes in M 2 amplitude around Iceland (Figure 4a) are of opposite sign compared to the March-September amplitude differences documented by Bij de Vaate et al (2021). This indicates that over time the annual average tide becomes closer to the September case, which is in line with interannual sea ice decline.…”

“…On the one hand, modifications of the tides can be the result of local processes, such as changes in coastal morphology or altered river flow (Haigh et al., 2020). On the other hand, observed variations in tides have been linked to regional climatic conditions, for example, the extent of sea ice coverage (e.g., Bij de Vaate et al., 2021; Müller et al., 2014; St‐Laurent et al., 2008), ocean stratification (e.g., Müller, 2012; Müller et al., 2014), and sea level rise (e.g., Devlin et al., 2017; Ross et al., 2017). Modeling studies suggest that climate change will continue to affect tides for centuries (Pickering et al., 2017; Schindelegger et al., 2018).…”

“…To gain more insight in the large‐scale secular changes in tides, we supplemented the clustered and sparsely distributed tide gauge dataset with data from satellite radar altimeters. Altimeter‐derived water levels are being widely used to estimate tidal constants, and have recently been used to study seasonal changes in tides (Bij de Vaate et al., 2021; Müller et al., 2014). However, up to now, only Ray (2016) used altimeter data from successive missions to compare the amplitude of the main semi‐diurnal tide (M 2 ) near Churchill, Hudson Bay (Canada).…”

“…

Knowledge of tides is important for many practical (e.g., marine navigation, fishery, coastal engineering) and scientific purposes. Although tide predictions often treat tidal harmonic constants as stationary over time, considerable changes in tides have been observed on seasonal (e.g., Bij de Vaate et al, 2021;Müller et al, 2014) to long-term timescales (e.g., Müller et al, 2011;Ray, 2016). On the one hand, modifications of the tides can be the result of local processes, such as changes in coastal morphology or altered river flow (Haigh et al, 2020).

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Secular Trends in Global Tides derived from Satellite Radar Altimetry

“…Knowledge of tides is important for many practical (e.g., marine navigation, fishery, coastal engineering) and scientific purposes. Although tide predictions often treat tidal harmonic constants as stationary over time, considerable changes in tides have been observed on seasonal (e.g., Bij de Vaate et al, 2021;Müller et al, 2014) to long-term timescales (e.g., Müller et al, 2011;Ray, 2016). On the one hand, modifications of the tides can be the result of local processes, such as changes in coastal morphology or altered river flow (Haigh et al, 2020).…”