Review: Potential catastrophic reduction of sea ice in the western Arctic Ocean: Its impact on biogeochemical cycles and marine ecosystems

Abstract

a b s t r a c tThe reduction of sea ice in the Arctic Ocean, which has progressed more rapidly than previously predicted, has the potential to cause multiple environmental stresses, including warming, acidification, and strengthened stratification of the ocean. Observational studies have been undertaken to detect the impacts on biogeochemical cycles and marine ecosystems of these environmental stresses in the Arctic Ocean. Satellite analyses show that the reduction of sea ice has been especially great in the western Arctic Ocean. Observations and model simulations have both helped to clarify the impact of sea-ice reductions on the dynamics of ecosystem processes and biogeochemical cycles. In this review, I focus on the western Arctic Ocean, which has experienced the most rapid retreat of sea ice in the Arctic Ocean and, very importantly, has a higher rate of primary production than any other area of the Arctic Ocean owing to the supply of nutrient-rich Pacific water. I report the impact of the current reduction of sea ice on marine biogeochemical cycles in the western Arctic Ocean, including lower-trophic-level organisms, and identify the key mechanism of changes in the biogeochemical cycles, based on published observations and model simulations. The retreat of sea ice has enhanced primary production and has increased the frequency of appearance of mesoscale anticyclonic eddies. These eddies enhance the light environment and replenish nutrients, and they also represent a mechanism that can increase the rate of the biological pump in the Arctic Ocean. Various unresolved issues that require further investigation, such as biological responses to environmental stressors such as ocean acidification, are also discussed.

Holocene dynamics in the Bering Strait inflow to the Arctic and the Beaufort Gyre circulation based on sedimentary records from the Chukchi Sea

“…High marine production in the Chukchi Sea of up to 400 g C m −2 y −1 in part is thought to reflect the high nutrient fluxes by the BSI (Walsh and Dieterle, 1994;Sakshaug, 2004). A recent enhancement of biological productivity and the biological pump in the Beaufort and Chukchi seas has been associated with the retreat of sea ice (summarized by Harada, 2016). This phenomenon is attributed to an increase in irradiance in the water column (Frey et al, 2011;Lee and Whitledge, 2005), wind-induced mixing that replenishes sea surface nutrients , and their combination (Nishino et al, 2009).…”

“…The Arctic currently faces rapid climate change caused by global warming (e.g., Screen and Simmonds, 2010;Harada, 2016). Changes in the current system of the Arctic Ocean regulate the state of Arctic sea ice and are involved in global processes via ice albedo feedback and the delivery of freshwater to the North Atlantic Ocean (Miller et al, 2010;Screen and Simmonds, 2010).…”

“…Changes in the current system of the Arctic Ocean regulate the state of Arctic sea ice and are involved in global processes via ice albedo feedback and the delivery of freshwater to the North Atlantic Ocean (Miller et al, 2010;Screen and Simmonds, 2010). The most significant consequence of this climate change during recent decades is the retreat of summer sea ice in the Pacific sector of the Arctic (e.g., Shimada et al, 2006;Harada, 2016, and references therein). Inflow of warm Pacific water through the Bering Strait (hereafter Bering Strait inflow -BSI) is suggested to have caused catastrophic changes in sea-ice stability in the western Arctic Ocean (Shimada et al, 2006).…”

Deep-sea benthic communities and oxygen fluxes in the Arctic Fram Strait controlled by sea-ice cover and water depth

“…As a consequence, the climate change induced alteration in the sea-ice cover influence biogeochemical cycles in the western Arctic (Harada, 2016). Further, arctic benthic oxygen flux model by Bourgeois et al (2017) showed a better fit when benthic chlorophyll data, indicating surface primary production patterns, were taken into account.…”

Towards the Marine Arctic Component of the Pan-Eurasian Experiment

“…Since the 1990s the Arctic climate has warmed at least twice as fast as the global mean (Francis and Vavrus, 2015) with associated dramatic declines in sea ice cover (Kwok and Cunnigham, 2015), terrestrial snow pack (Derksen et al, 2015) and 5 permafrost (Lawrence et al, 2015), coincident with increase in continental freshwater discharge into the Arctic Ocean (Carmack et al, 2016) and changes in the biochemical cycle (Shakhova et al 2007;Harada, 2016). These changes have strong socio-economic and environmental impacts.…”