Recent research suggests that natural variations in the Earth's climate have contributed to the observed loss of Arctic sea ice. Two specific factors contributing to this decline are:

1. Pacific Decadal Oscillation (PDO): The PDO is a natural fluctuation in the Pacific Ocean's surface temperatures. During its warm phase, the PDO leads to increased sea surface temperatures in the North Pacific, affecting atmospheric circulation patterns and resulting in reduced sea ice cover in the Arctic.

2. Atlantic Multidecadal Oscillation (AMO): Similar to the PDO, the AMO is a long-term variation in the Atlantic Ocean's surface temperatures. Its warm phase is associated with increased ocean heat transport into the Arctic, leading to reduced sea ice extent.

These natural climate cycles can influence Arctic sea ice cover on decadal timescales. However, it's important to note that human-induced climate change, primarily driven by the emission of greenhouse gases, remains the dominant driver of Arctic sea ice loss. While natural variations can contribute to short-term fluctuations, the long-term decline in Arctic sea ice is predominantly attributed to anthropogenic factors.