Abstract
Abstract. Many studies have shown a decrease in Arctic sea ice extent. It does not logically follow, however, that the extent of the marginal ice zone (MIZ), here defined as the area of the ocean with ice concentrations from 15 % to 80 %, is also changing. Changes in the MIZ extent has implications for the level of atmospheric and ocean heat and gas exchange in the area of partially ice-covered ocean and for the extent of habitat for organisms that rely on the MIZ, from primary producers like sea ice algae to seals and birds. Here, we present, for the first time, an analysis of satellite observations of pan-Arctic averaged MIZ extent. We find no trend in the MIZ extent over the last 40 years from observations. Our results indicate that the constancy of the MIZ extent is the result of an observed increase in width of the MIZ being compensated for by a decrease in the perimeter of the MIZ as it moves further north. We present simulations from a coupled sea ice–ocean mixed layer model using a prognostic floe size distribution, which we find is consistent with, but poorly constrained by, existing satellite observations of pan-Arctic MIZ extent. We provide seasonal upper and lower bounds on MIZ extent based on the four satellite-derived sea ice concentration datasets used. We find a large and significant increase (>50 %) in the August and September MIZ fraction (MIZ extent divided by sea ice extent) for the Bootstrap and OSI-450 observational datasets, which can be attributed to the reduction in total sea ice extent. Given the results of this study, we suggest that references to “rapid changes” in the MIZ should remain cautious and provide a specific and clear definition of both the MIZ itself and also the property of the MIZ that is changing.
Highlights
Arctic sea ice extent has been declining rapidly over the last 40 years (Comiso et al, 2008; Onarheim et al, 2018; Serreze et al, 2007; Stroeve et al, 2007)
The definition of the marginal ice zone (MIZ) using ocean wave penetration can be very useful for other studies, we argue that comparisons of purely MIZ extent from different observational datasets and models should be done through sea ice concentration thresholds
We have found no significant trend in the MIZ extent across any of the observational datasets examined here (OSI-450, Bootstrap, and AMSR), with the exception of a small negative trend in March for Bootstrap
Summary
Arctic sea ice extent has been declining rapidly over the last 40 years (Comiso et al, 2008; Onarheim et al, 2018; Serreze et al, 2007; Stroeve et al, 2007). The marginal ice zone (MIZ) has been variously defined as where ocean windgenerated waves interact with the sea ice (e.g., Dumont et al, 2011) or as the area of ocean covered with 15 %–80 % sea ice (e.g., Aksenov et al, 2017; Strong and Rigor, 2013). Given the rapid decline of sea ice extent in the Arctic, associated studies tend to assume that the marginal ice zone (MIZ) is expanding (Boutin et al, 2020; Lee and Thomson, 2017; Strong et al, 2017; Horvat and Tziperman, 2015). As the Arctic MIZ moves northwards (Aksenov et al, 2017), the increased southward area of open ocean subsequently allows for increased wind wave generation, which can break up the ice (Collins et al, 2015; Thomson and Rogers, 2014).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
