Regime shift in Arctic Ocean sea ice thickness

Abstract

Manifestations of climate change are often shown as gradual changes in physical or biogeochemical properties1. Components of the climate system, however, can show stepwise shifts from one regime to another, as a nonlinear response of the system to a changing forcing2. Here we show that the Arctic sea ice regime shifted in 2007 from thicker and deformed to thinner and more uniform ice cover. Continuous sea ice monitoring in the Fram Strait over the last three decades revealed the shift. After the shift, the fraction of thick and deformed ice dropped by half and has not recovered to date. The timing of the shift was preceded by a two-step reduction in residence time of sea ice in the Arctic Basin, initiated first in 2005 and followed by 2007. We demonstrate that a simple model describing the stochastic process of dynamic sea ice thickening explains the observed ice thickness changes as a result of the reduced residence time. Our study highlights the long-lasting impact of climate change on the Arctic sea ice through reduced residence time and its connection to the coupled ocean–sea ice processes in the adjacent marginal seas and shelves of the Arctic Ocean.

Fluctuating Atlantic inflows modulate Arctic atlantification

“…For example, despite increased ice-area export (Fig. 2D), decreased ice thickness in the Fram Strait ( 10 ) may cause a decline in ice volume export, which would offset the decline in net ice production in high-latitude regions ( 47 ). In contrast to the Amerasian Basin, ventilation of the upper Eurasian Basin in the 2010s is well documented ( 5 , 9 , 36 ), and sea-ice loss in this basin continued through the 2010s (Fig.…”

“…Thus, a more stable regime of Arctic sea ice appears to have begun in 2007. This transition was abrupt, with 2007 setting a record for a single-year sea-ice–extent decrease of −1.6 × 10 6 km 2 (compare with 2012’s second record-year drop of −1.0 × 10 6 km 2 ) ( 10 ).…”

Stronger Arctic amplification produced by decreasing, not increasing, CO2 concentrations

“…More efforts are needed to advance our understanding of the feedback processes and/or radiative forcing contributing to Arctic asymmetry, which could intrinsically build upon the non-linearity in Arctic climate response (e.g. Deng et al 2020, Sumata et al 2023.…”

Modeling the Recent Changes of Phytoplankton Blooms Dynamics in the Arctic Ocean

“…In the ECCO2-Darwin model the photosynthetic available radiating (PAR) is computed at each vertical and it is used in the formulation proposed by Geider et al (1997) in order to compute the contribution of light limitation to phytoplankton growth. In the current version of our model we do not have a specific treatment of PAR penetration through the sea-ice medium that would allow a representation of the PAR increase under sea ice as it becomes thinner due to Arctic climate warming (Kwok, 2018;Sumata et al, 2023). Therefore, due to this current deficiency the model cannot represent any under-ice blooms of phytoplankton in the subsurface Arctic waters.…”

“…Recent Arctic climate warming has caused a progressive and well‐documented decline of Arctic Ocean (AO) sea‐ice thickness and extent (Comiso et al., 2008; Kacimi & Kwok, 2022; Kwok, 2018; Laxon et al., 2013; Parkinson & Comiso, 2013; Sumata et al., 2023; J. Stroeve et al., 2007) accompanied by an AO surface warming trend (Z. Li et al., 2022; Shu et al., 2022; Steele et al., 2008) and mostly due to a well‐documented climate warming trend (Rantanen et al., 2022). However, the current spatial and temporal variations in AO stratification seem to be controlled not only by the sea‐ice melting and ocean warming but also by the intensity of the wind and of the riverine freshwater runoff (Hordoir et al., 2022).…”