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Historically, multiyear sea ice (MYI) covered a majority of the Arctic and circulated through the Beaufort Gyre for years. However, increased ice melt in the Beaufort Sea during the early 2000s was proposed to have severed this circulation. Constructing a regional MYI budget from 1997 to 2021 reveals that MYI import into the Beaufort Sea has increased year‐round, yet less MYI now survives through summer and is transported onwards in the Gyre. Annual average MYI loss quadrupled over the study period and increased from ∼7% to ∼33% of annual Fram Strait MYI export, while the peak in 2018 (385,000 km2) was similar in magnitude to Fram Strait MYI export. The ice‐albedo feedback coupled with the transition toward younger thinner MYI is responsible for the increased MYI loss. MYI transport through the Beaufort Gyre has not been severed, but it has been reduced so severely to prevent it from being redistributed throughout the Arctic Ocean. Plain Language Summary: Historically, sea ice grew thicker and aged into multiyear sea ice (MYI) as it was transported clockwise around the Beaufort Gyre for up to and beyond 10 years. This pattern facilitated the pan‐Arctic distribution of MYI that was typical of the 1980s and 1990s. However, warming temperatures and greater sea ice melt in the Beaufort Sea since the early 2000s have significantly increased the annual area of MYI lost to melt and was proposed to have severed MYI transport through the Beaufort Gyre. Here, we use a regional MYI budget to show that an increasing area of MYI is lost annually in the Beaufort Sea and that this has considerably altered and interrupted MYI transport through the Gyre for prolonged periods during recent years. This change has implications regionally for wildlife, shipping, and local communities, while also having an effect on the resiliency of the pan‐Arctic ice pack. Key Points: Multiyear sea ice (MYI) area loss in the Beaufort Sea quadrupled from 46,000 km2/yr−1 in 1997–2001 to 183,000 km2/yr−1 in 2017–2021MYI area loss peaked at 385,000 km2 in 2018, which is close to the annual MYI area export through Fram StraitThe Beaufort Sea has become a MYI export pathway rivaling the Fram Strait, encouraging the pan‐Arctic transition to a seasonal ice cover [ABSTRACT FROM AUTHOR]

Ice arches in the Canadian Arctic Archipelago (CAA) block the inflow of Arctic Ocean ice for the majority of the year. A 22 year record (1997–2018) of Arctic Ocean‐CAA ice exchange was used to investigate the effect of warming on CAA sea ice dynamics. Larger ice area flux values were associated with longer flow duration and faster ice speed facilitated by increased open water leeway from the CAA's transition to a younger and thinner ice regime, which together have contributed to a significant ice area flux increase (103 km2/year) from Arctic Ocean into the northern CAA from 1997 to 2018. Remarkably, the 2016 Arctic Ocean ice area flux into the CAA (161 × 103 km2) was 7 times greater than the 1997–2018 average (23 × 103 km2) and almost double the 2007 ice area flux into Nares Strait (87 × 103 km2). Continued warming may result in the CAA becoming a larger outlet for Arctic Ocean ice area loss. Plan Language Summary: Satellite observations are used to understand the effect of warmer temperatures on how much sea ice is transferred between the Canadian Arctic Archipelago (CAA) and the Arctic Ocean. Larger sea ice area flux values are associated with (i) longer flow duration, (ii) faster moving ice, and (iii) more open water leeway from the CAA's long‐term transition to a younger and thinner ice regime. These factors have contributed to a significant increase in the amount of sea ice entering the northern regions of the CAA from 1997 to 2018. Remarkably, the amount of Arctic Ocean ice entering the CAA in 2016 was 7 times larger the 1997–2018 average and almost double that of the amount of ice transported through Nares Strait in 2007. Overall, with continued warming the CAA could be larger pathway for the loss of sea ice in the Arctic Ocean. Key Points: Significant increase of Arctic Ocean ice area flux into the northern CAA from 1997 to 2018Arctic Ocean ice area flux into the CAA in 2016 was 7 times greater than 1997–2018 averageContinued warming may result in the CAA becoming a larger outlet for Arctic Ocean ice area loss [ABSTRACT FROM AUTHOR]

Abstract: Spring melt pond fraction (fp) has been shown to influence September sea ice extent and, with a growing need to improve melt pond physics in climate and forecast models, observations at large spatial scales are needed. We present a novel technique for estimating fp on sea ice at high spatial resolution from the Sentinel‐1 satellite during the winter period leading up to spring melt. A strong correlation (r = −0.85) is found between winter radar backscatter and fp from first‐year and multiyear sea ice data collected in the Canadian Arctic Archipelago (CAA) in 2015. Observations made in the CAA in 2016 are used to validate a fp retrieval algorithm, and a fp prediction for the CAA in 2017 is made. The method is effective using the horizontal transmit and receive polarization channel only and shows promise for providing seasonal, pan‐Arctic, fp maps for improved understanding of melt pond distributions and forecast model skill. [ABSTRACT FROM AUTHOR]

Snowmelt onset and end date estimates are made from QuikSCAT scatterometer measurements in the Canadian High Arctic wetland of Polar Bear Pass (PBP) and the surrounding region of Bathurst Island, Nunavut. In situ data within PBP is used to validate QuikSCAT snowmelt onset/end date estimates. Results indicate that within PBP from 2000 to 2009, the mean snowmelt onset date was Year Day (YD) 162, the mean snowmelt end date was YD179, and the mean snowmelt duration was 17 days. More interannual variability was apparent in snowmelt end date and duration compared with onset, and only snowmelt end date was significantly correlated with mean June air temperature at −0.78. Cooler air temperatures in 2004 contributed to a long snowmelt duration of 24 days, and the very short snowmelt duration in 2007 of just 11 days was caused by rapid and sustained increases in air temperature. For snowmelt end date and duration the mean spatial pattern revealed two centres of later snowmelt end date/longer snowmelt duration over Bathurst Island. They were separated by early snowmelt end date/short snowmelt duration in PBP. These patterns are in agreement with the spatial distribution of mean May to July air temperature over Bathurst Island and are likely influenced by the local-scale topography of Bathurst Island. Given the correlation between air temperature and snowmelt end date, we might expect quicker snowmelt under increased warming. The latter process may have implications for the sustainability of the PBP wetland under a warmer climate. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]