The Stepwise Reduction of Multiyear Sea Ice Area in the Arctic Ocean
Since 1980.
Abstract
The loss of multiyear sea ice (MYI) in the Arctic Ocean is a significant
change that affects all facets of the Arctic environment. Using a
lagrangian ice age product we examine MYI loss and quantify the annual
MYI area budget from 1980-2021 as the balance of export, melt and
replenishment. Overall, MYI area declined at 72,500 km^2/yr, however a
majority of the loss occurred during two stepwise reductions that
interrupt an otherwise balanced budget and resulted in northward
contractions of the MYI pack. First, in 1989, a change in atmospheric
forcing led to a +56% anomaly in MYI export through Fram Strait. The
second occurred from 2006-2008 with anomalously high melt (+25%) and
export (+23%) coupled with low replenishment (-8%). In terms of
trends, melt has increased since 1989, particularly in the Beaufort Sea,
export has decreased since 2008 due to reduced MYI coverage north of
Fram Strait, and replenishment has increased over the full time series
due to a negative feedback that promotes seasonal ice survival at higher
latitudes exposed by MYI loss. However, retention to older MYI has
significantly declined, transitioning the MYI pack towards younger MYI
that is less resilient than previously anticipated and could soon elicit
another stepwise reduction. We speculate that future MYI loss will be
driven by increased melt and reduced replenishment, both of which are
enhanced with continued warming and will one day render the Arctic Ocean
free of MYI, a change that will coincide with a seasonally ice-free
Arctic Ocean.