Changing Biogeochemistry of the Southern Ocean and Its Ecosystem Implications

Henley, Sian F.; Cavan, Emma L.; Fawcett, Sarah E.; Kerr, Rodrigo; Monteiro, Thiago; Sherrell, Robert M.; Bowie, Andrew R.; Boyd, Philip W.; Barnes, David K. A.; Schloss, Irene R; Marshall, Tanya; Smith, S.

doi:10.3389/fmars.2020.00581

Cited by 145 publications

(170 citation statements)

References 331 publications

(479 reference statements)

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“…Nevertheless, there is good agreement amongst CMIP5 models that Southern Ocean NPP will increase overall as a result of increased iron supply, changes in mixed layer depth, declining sea ice cover, increasing SST and altered westerly winds (Bopp et al, 2013;Leung et al, 2015;Fu et al, 2016;Moore et al, 2018). Increased iron supply and temperature could also lead to a floristic shift to diatoms and potentially Phaeocystis antarctica, with consequences for benthic and pelagic consumers as well as nutrient uptake, carbon export and large-scale biogeochemical cycling (Henley et al, 2020).…”

Section: Increasing Iron Inputs and Freshwater Flux From Glacial Ice mentioning

confidence: 95%

“…One of the most important functions of the SO in the Earth System is its uptake of atmospheric CO 2 by physical and biological processes and its release of oceanic CO 2 to the atmosphere (Sarmiento and Le Quere, 1996;Marinov et al, 2006;Gruber et al, 2009Gruber et al, , 2019Lenton et al, 2013;Henley et al, 2020 this volume). However, this uptake is leading to changes in ocean biogeochemistry, which could have devastating consequences for the ecosystem.…”

Section: Biogeochemistry Co 2 Uptake and Ocean Acidificationmentioning

confidence: 99%

“…Ocean acidification driven by oceanic uptake of atmospheric CO 2 is expected to occur earlier in the SO than most other ocean regions, due to enhanced solubility of CO 2 at low temperature and upwelling of deep waters with high CO 2 concentrations (Orr et al, 2005;McNeil and Matear, 2008;Feely et al, 2009). Ongoing changes in upper ocean temperature and salinity are very likely to impact the solubility of CO 2 in SO surface waters, and projected increases in the Revelle factor are expected to increase the biologically mediated uptake of CO 2 over the twenty-first century Henley et al, 2020).…”

Section: Biogeochemistry Co 2 Uptake and Ocean Acidificationmentioning

confidence: 99%

“…The ASH is expected to shoal to the surface during winter periods from ∼2,030 and across all seasons by 2100 (Orr et al, 2005;McNeil and Matear, 2008;McNeil et al, 2010;IPCC, 2019). This is likely to impact upon phytoplankton abundance, growth rates and species composition as well as zooplankton growth, reproductive success and survival, especially of ecologically important species of pteropods and krill (Tortell et al, 2008;Kawaguchi et al, 2013;Trimborn et al, 2013;Gardner et al, 2018;Henley et al, 2020). Mg-calcites are more soluble than aragonite and Southern Ocean surface waters are already undersaturated for ≥ 12 mol% MgCO 3 and are predicted to become undersaturated for 4-5% mol% MgCO 3 by 2100 (Andersson et al, 2008).…”

Section: Biogeochemistry Co 2 Uptake and Ocean Acidificationmentioning

confidence: 99%

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Global Drivers on Southern Ocean Ecosystems: Changing Physical Environments and Anthropogenic Pressures in an Earth System

et al. 2020

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The manuscript assesses the current and expected future global drivers of Southern Ocean (SO) ecosystems. Atmospheric ozone depletion over the Antarctic since the 1970s, has been a key driver, resulting in springtime cooling of the stratosphere and intensification of the polar vortex, increasing the frequency of positive phases of the Southern Annular Mode (SAM). This increases warm air-flow over the East Pacific sector (Western Antarctic Peninsula) and cold air flow over the West Pacific sector. SAM as well as El Niño Southern Oscillation events also affect the Amundsen Sea Low leading to either positive or negative sea ice anomalies in the west and east Pacific sectors, respectively. The strengthening of westerly winds is also linked to shoaling of deep warmer water onto the continental shelves, particularly in the East Pacific and Atlantic sectors. Air and ocean warming has led to changes in the cryosphere, with glacial and ice sheet melting in both sectors, opening up new ice free areas to biological productivity, but increasing seafloor disturbance by icebergs. The increased melting is correlated with a salinity decrease particularly in the surface 100 m. Such processes could increase the availability of iron, which is currently limiting primary production over much of the SO. Increasing CO2 is one of the most important SO anthropogenic drivers and is likely to affect marine ecosystems in the coming decades. While levels of many pollutants are lower than elsewhere, persistent organic pollutants (POPs) and plastics have been detected in the SO, with concentrations likely enhanced by migratory species. With increased marine traffic and weakening of ocean barriers the risk of the establishment of non-indigenous species is increased. The continued recovery of the ozone hole creates uncertainty over the reversal in sea ice trends, especially in the light of the abrupt transition from record high to record low Antarctic sea ice extent since spring 2016. The current rate of change in physical and anthropogenic drivers is certain to impact the Marine Ecosystem Assessment of the Southern Ocean (MEASO) region in the near future and will have a wide range of impacts across the marine ecosystem.

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Section: Increasing Iron Inputs and Freshwater Flux From Glacial Ice mentioning

confidence: 95%

Section: Biogeochemistry Co 2 Uptake and Ocean Acidificationmentioning

confidence: 99%

Section: Biogeochemistry Co 2 Uptake and Ocean Acidificationmentioning

confidence: 99%

Section: Biogeochemistry Co 2 Uptake and Ocean Acidificationmentioning

confidence: 99%

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Global Drivers on Southern Ocean Ecosystems: Changing Physical Environments and Anthropogenic Pressures in an Earth System

et al. 2020

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“…While covering only 30% of the global ocean's surface, it is predicted to account up to 75% of the heat uptake (Frölicher et al, 2015), underlining its importance under the reported and predicted impacts of anthropogenic-driven climate change. Thus, a better understanding of Southern Ocean processes on a circumpolar and regional scales and their vulnerability is urgent, especially considering that climate-driven changes over its biogeochemistry likely to impact from primary producers to changes on the ecosystem functioning (Henley et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Changes in Phytoplankton Communities Along the Northern Antarctic Peninsula: Causes, Impacts and Research Priorities

et al. 2020

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The Northern Antarctic Peninsula (NAP), located in West Antarctica, is amongst the most impacted regions by recent warming events. Its vulnerability to climate change has already led to an accumulation of severe changes along its ecosystems. This work reviews the current findings on impacts observed in phytoplankton communities occurring in the NAP, with a focus on its causes, consequences, and the potential research priorities toward an integrated comprehension of the physicalbiological coupling and climate perspective. Evident changes in phytoplankton biomass, community composition and size structure, as well as potential bottom-up impacts to the ecosystem are discussed. Surface wind, sea ice and meltwater dynamics, as key drivers of the upper layer structure, are identified as the leading factors shaping phytoplankton. Short-and long-term scenarios are suggested for phytoplankton communities in the NAP, both indicating a future increase of the importance of small flagellates at the expense of diatoms, with potential devastating impacts for the ecosystem. Five main research gaps in the current understanding of the phytoplankton response to climate change in the region are identified: (i) anthropogenic signal has yet to be disentangled from natural climate variability; (ii) the influence of small-scale ocean circulation processes on phytoplankton is poorly understood; (iii) the potential consequences to regional food webs must be clarified; (iv) the magnitude and risk of potential changes in phytoplankton composition is relatively unknown; and (v) a better understanding of phytoplankton physiological responses to changes in the environmental conditions is required. Future research directions, along with specific suggestions on how to follow them, are equally suggested. Overall, while the current

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