Abstract
Glaciers in the Arctic respond sensitively to climate change, recording the polar amplification of global warming with increasing mass loss. Here, we use glacier mass balances in Svalbard and northern Arctic Canada to categorize tropospheric variability and the associated summer circulation over the Arctic. We establish a link between annual glacier mass balances and their respective atmospheric forcings since 1950 using GRACE/GRACE-FO satellite data (2002–2021), as well as regional climate models and reanalysis data (1950–2019). We find that asynchronous behaviour of mass balance between the regions has become very likely since the early 2000s, exceeding the range of previous decadal variability. Related tropospheric circulation exhibits more meridional patterns, a greater influence of meridional heat advection and a wavier summer circulation. The traceable impact on glacier mass balances emphasizes the importance of dynamic next to thermodynamic climate changes for the future of glacier mass loss, Arctic ecology and societal impacts.
Highlights
Glaciers in the Arctic respond sensitively to climate change, recording the polar amplification of global warming with increasing mass loss
We show that years with predominantly meridional circulation have become more frequent in the past two decades, superseding zonal circulation patterns since the late 1990s (Figs. 4 and 5e)
The occurrence of years associated with zonal circulation drops from roughly 73% in the time frame 1963–1977 to only 20% during 2004–2018 (Supplementary Table 1)
Summary
Highest positive and negative mass-balance correlations (Fig. 2b). We focus on the months June, July and August (JJA) as fluctuations in the summer melt rate cause the greatest year-to-year variability in the annual mass balances of both regions (75% for ACN and 68% for SVA)[11,17,18] (Extended Data Fig. 3). Employing GRACE/GRACE-FO mass-balance anomalies instead of SMB anomalies for 2004–2018 produces very consistent correlation patterns with z500 and northward heat flux (Extended Data Fig. 5). Reduced northward heat flux slightly south of ACN prevails during times of positive mass-balance anomalies (reduced melt conditions), while SVA experiences enhanced northward heat flux (enhanced melt conditions), and the other way around This alternating relationship with its spatial similarity has manifested itself only in recent years. Starting in the early 2000s, asynchronous behaviour has become very likely (following the IPCC definitions28), with probabilities exceeding the significance threshold of 5% for the 15 yr bin centred on 2004 (Fig. 4) This underpins the strong anti-correlations shown, promoted by an increasing magnitude of mass-balance variability seen in the recent two decades The uncertainties in the z500 composites arising from uncertainties in the SMB reconstruction are presented in Extended Data Fig. 10
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