Mechanisms and Atmospheric Drivers of Arctic Multiyear Sea Ice Loss

Abstract Employing the spaceborne observations from scatterometers (QuikSCAT and ASCAT), we quantify the contributions of different mechanisms to the Arctic MYI area changes over two decades (1999/2000–2017/2018). Specifically, the loss mechanisms (export, melt, deformation) and gain mechanism (replenishment) associated with MYI area variations are examined. On average, there was an annual (October‐September) MYI area loss of 1,080.3 × 10 3 km 2 due to export, melt, and deformation of 749.2 × 10 3 km 2 , 222.5 × 10 3 km 2 , and 108.6 × 10 3 km 2 , respectively. The substantial MYI depletion was largely offset by replenishment from the aging of first‐year ice (FYI) at the end of the melt season, which on average amounted to 993.8 × 10 3 km 2 in the Arctic Ocean. Therefore, a net annual MYI area loss of −86.5 × 10 3 km 2 emerged in the Arctic. The consecutive occurrence of the anomalously low MYI replenishment from 2005 to 2007 was responsible for the dramatic decadal decline of MYI area between the QuikSCAT (P1:2000‐2008) and ASCAT (P2: 2009–2018) periods from 3.29 × 10 6 km 2 during P1 dropping a half to 1.61 × 10 6 km 2 during P2. Moreover, the recently enhanced melt and deformation processes were favorable in maintaining the Arctic MYI at the low‐level coverage during P2 relative to P1. The thermodynamic (melt and replenishment) and dynamic mechanisms (export) related to MYI variations are linked to Dipole Anomaly (DA), whereas North Atlantic Oscillation (NAO) acts to influence the thermodynamic mechanism (melt and replenishment). On the other hand, no significant connection is identified for Arctic Oscillation (AO) or Barents‐Beaufort Oscillation (BBO).