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Ocean acidification is the hydrogen ion increase caused by the oceanic uptake of anthropogenic CO2, and is a focal point in marine biogeochemistry, in part, because this chemical reaction reduces calcium carbonate (CaCO3) saturation states (Ω) to levels that are corrosive (i.e. Ω ≤ 1) to shell-forming marine organisms. However, other processes can drive CaCO3 corrosivity; specifically, the addition of tidewater glacial melt. Carbonate system data collected in May and September from 2009 through 2012 in Prince William Sound (PWS), a semi-enclosed inland sea located on the south-central coast of Alaska that is ringed with fjords containing tidewater glaciers, reveal the unique impact of glacial melt on CaCO3 corrosivity. Initial limited sampling was expanded in September 2011 to span large portions of the western and central sound, and included two fjords proximal to tidewater glaciers: Icy Bay and Columbia Bay. The observed conditions in these fjords affected CaCO3 corrosivity in the upper water column (< 50 m) in PWS in two ways: (1) as spring-time formation sites of mode water with near-corrosive Ω levels seen below the mixed layer across the sound, and (2) as point sources for surface plumes of glacial melt with corrosive Ω levels (Ω for aragonite and calcite down to 0.60 and 1.02, respectively) and carbon dioxide partial pressures (pCO2) well below atmospheric levels. CaCO3 corrosivity in glacial melt plumes is poorly reflected by pCO2 or pHT, indicating that either one of these carbonate parameters alone would 20 fail to track Ω in PWS. The unique Ω and pCO2 conditions in the glacial melt plumes enhances atmospheric CO2 uptake, which, if not offset by mixing or primary productivity, would rapidly exacerbate CaCO3 corrosivity in a positive feedback. The cumulative effects of glacial melt and air-sea gas exchange are likely responsible for the seasonal widespread reduction of Ω in PWS; making PWS highly sensitive to increasing atmospheric CO2 and amplified CaCO3 corrosivity. [ABSTRACT FROM AUTHOR]

The Arctic Ocean accounts for only 4 % of the global ocean area, but it contributes significantly to the global carbon cycle. Recent observations of seawater CO2-carbonate chemistry in shelf waters of the western Arctic Ocean, primarily in the Chukchi Sea, from 2009 to 2011 indicate that bottom waters are seasonally undersaturated with respect to calcium carbonate (CaCO3) minerals, particularly aragonite. Nearly 40 % of sampled bottom waters on the shelf have saturation states less than one for aragonite (i.e., Ωaragonite < 1.0), thereby exposing the benthos to potentially corrosive water for CaCO3 -secreting organisms, while 80 % of bottom waters present had Ωaragonite values less than 1.5. Our observations indicate seasonal reduction of saturation states (Ω) for calcite (Ωaragonite) and aragonite (Ωaragonite) in the subsurface in the western Arctic by as much as 0.8 and 0.5, respectively. Such data indicate that bottom waters of the western Arctic shelves were already potentially corrosive forbiogenic and sedimentary CaCO3 for several months each year. Seasonal changes in Ω are imparted by a variety of factors such as phytoplankton photosynthesis, respi-ration/remineralization of organic matter and air-sea gas exchange of CO2. Combined, these processes either increase or enhance in surface and subsurface waters, respectively. These seasonal physical and biological processes also act to mitigate or enhance the impact of Anthropocene ocean acidification (OA) on Ω in surface and subsurface waters, respectively. Future monitoring of the western Arctic shelves is warranted to assess the present and future impact of ocean acidification and seasonal physico-biogeochemical processes on Ω values and Arctic marine ecosystems. [ABSTRACT FROM AUTHOR]

The Arctic Ocean accounts for only 4% of the global ocean area but it contributes significantly to the global carbon cycle. Recent observations of seawater carbonate chemistry in shelf waters of the Western Arctic from 2009 to 2011 indicate that extensive areas of the benthos are exposed to bottom waters that are seasonally undersaturated with respect to calcium carbonate (CaCO3) minerals, particularly aragonite. Our observations indicate seasonal reduction of saturation states (ω) for calcite (ωcalcite) and aragonite (ωaragonite) in the subsurface in the Western Arctic by as much as 0.9 and 0.6, respectively. Such data indicates that bottom waters of the Western Arctic shelves are already potentially corrosive for biogenic and sedimentary CaCO3 for several months each year. Seasonal changes in ω are imparted by a variety of factors such as phytoplankton photosynthesis, respiration/remineralization of organic matter and air-sea gas exchange of CO2 - combined these processes either increase or enhance ω in surface and subsurface waters, respectively. These seasonal physical and biological processes also act to mitigate or enhance the impact of Anthropocene ocean acidification (OA) on ω in surface and subsurface waters, respectively. Future monitoring of the Western Arctic shelves is warranted to assess the present and future impact on ω values from ocean acidification and seasonal biological/physical processes on Arctic marine ecosystems. [ABSTRACT FROM AUTHOR]

The article discusses the research which shows that the Arctic Ocean has rapidly acidified over several decades because of the oceanic uptake of anthropogenic carbon dioxide from the atmosphere. It states that ocean acidification is one of the most prominent issues in marine research as a potential biological threat to marine calcifiers such as clams and pteropods and associated fisheries and its impacts to humans.

The article reports on the progression of ocean acidification in the Arctic in 2013. Topics discussed include the uptake of anthropogenic carbon dioxide from the atmosphere, the history of ocean acidification studies in the Arctic Ocean, and the drivers of carbonate mineral undersaturations over the Arctic continental shelves.