Abstract
Marine ice is retreating in many sectors of Earth’s polar and subpolar
regions. The rates are unprecedented, generating great concern in both
scientific and public communities. Despite the expected serious
implications, we lack a comprehensive understanding of how ice loss and
related processes control marine biota and interactions at different
spatiotemporal scales under multiple environmental stressors and drivers
of change. We systematically review existing knowledge on how the losses
of ice shelves, sea ice, and glaciers affect polar marine biocenosis. We
include in situ, remote sensing, and modelling studies on sea ice biota,
phyto- and zooplankton, fish, seabirds, phyto- and zoobenthos and marine
mammals, covering a time span of three decades (1991-2022). We apply a
qualitative ecosystem‐based risk assessment to assess the individual and
cumulative response of ecosystem components and related ecosystem
services. The most threats and opportunities are expected to manifest in
the shallow coastal zones. They include loss of ice habitat, water
column darkening due to sediment input with meltwater, increased
sedimentation rates, and mechanical damage due to ice scouring, but also
gain of marine habitat, lightening of the water column and nutrient
input with meltwater. The cumulative score of all the stressors shows
that marine ice loss will lead to autotroph-dominated polar marine
systems with detrimental effects on secondary producers, i.e.
zooplankton and zoobenthos, and sea ice-obligate species. Although
similar stressors are recognised for polar and subpolar regions, some
processes may differ in magnitude. This overview aims to provide
summarised knowledge to inform science-based solutions for conservation
and climate mitigation actions.
Keywords: cryosphere retreat, ecosystem change, polar
biocenosis, Arctic and Southern Ocean
Introduction
Polar regions are experiencing some of the most extreme climate change
impacts that have already resulted in serious transformations. In
particular, polar marine ecosystems are strongly influenced by the
rapidly-changing extent, duration, and seasonality of the cryosphere
(Fig.1). Loss of marine ice, i.e. ice shelves, glaciers, and sea ice, is
an undeniable indicator of ongoing climatic changes on Earth (Cavalieri
and Parkinson 2012, Parkinson and Cavalieri 2012, Pfeffer et al. 2014).
The estimates derived from satellite observations and numerical models
show that Earth has lost 28 x 1012 t of ice between 1994 and 2017,
including Arctic sea ice (7.6 x 1012 t), Antarctic ice shelves (6.5 x
1012 t), the Greenland ice sheet (3.8 x1012 t), the Antarctic ice sheet
(2.5 x 1012t), and Southern Ocean sea ice (0.9 x1012t) (Slater et al.
2021). Despite the legally-binding Agreement to constrain warming to
1.5°C above pre-industrial levels (UNFCCC 2015), the cryosphere will
continue to lose mass this century (Pattyn et al. 2018) and post-breakup
recovery of confined ice shelves is unlikely (Åkesson et al. 2022).