Inorganic carbon and pH levels in the Rockall Trough 1991–2010

The accumulation of anthropogenic CO2 in the oceans is altering seawater carbonate chemistry. Investigation and monitoring of the carbonate parameters is therefore necessary to understand potential impacts on ocean ecosystems. Total alkalinity (AT) and dissolved inorganic carbon (CT) were sampled across the Rockall Trough in Feb 2009 (CE0903) and Feb 2010 (CE10002) as part of a baseline study of inorganic carbon chemistry in Irish shelf waters. The results have been compared with data from WOCE surveys A01E (Sept 1991), A01 (Dec 1994), AR24 (Nov 1996), and A24 (June 1997). The 2009 and 2010 datasets provide a snapshot of the biogeochemical parameters which can act as a baseline of inorganic carbon and acidity levels in surface waters of the Rockall Trough in late winter for future comparison since previous surveys in the area have been affected by biological activity. The dataset also offers the possibility to compare decadal changes in subsurface waters. The temporal evolution of anthropogenic carbon (ΔCant) between the 1990s and 2010 was evaluated using two separate methods; (i) a comparison of the concentrations of CT between surveys, after correcting it for remineralisation of organic material and formation and dissolution of calcium carbonate (ΔCT-abio) and (ii) an extended Multiple Linear Regression was used to calculate the ΔCant (ΔCanteMLR). There was an increase in ΔCT-abio and ΔCanteMLR of 18±4μmol kg-1 and 19±4μmol kg-1, respectively, in the subsurface waters between 1991 and 2010, equivalent to a decrease of 0.040±0.003 pH units over the 19 year period. There was an increase in both ΔCT-abio and ΔCanteMLR of 8±4μmol kg-1 in Labrador Sea Water (LSW) in the Trough between 1991 and 2010, and LSW has acidified by 0.029±0.002 pH units over the same time period. A reduction in calcite and aragonite saturation states was observed, which may have implications for calcifying organisms in the region.

McGrath T., Kivimäe C., Tanhua T., Cave R. R. & McGovern E., in press. Inorganic carbon and pH levels in the Rockall Trough 1991–2010. Deep Sea Research Part I: Oceanographic Research Papers. doi: 10.1016/j.dsr.2012.05.011. Article (subscription required).

1 Response to “Inorganic carbon and pH levels in the Rockall Trough 1991–2010”

  1. 1 Larry Lawhorn 21 June 2012 at 16:31

    ..::”Ocean Acidification is now irreversible… at least on timescales of at least… TENS of THOUSANDS of years…

    Even with stabilisation of atmospheric CO2 at 450 ppm, Ocean Acidification will have profound impacts (death and extinction) on many marine systems.

    LARGE and rapid reductions of global CO2 emissions are needed globally by at LEAST 50% by 2050.

    Analysis of past events in Earth’s geologic history suggests that chemical recovery (normal pH for LIFE in the Ocean) will take TENS of THOUSANDS of years – while the recovery of ecosystem function and biological diversity (LIFE AS WE KNOW IT) can take much longer. (MILLIONS OF YEARS)

    ..:: “Every day, 70 MILLION TONS of CO2 are released into Earth’s atmosphere. ( remaining in the atmosphere for thousands of years )

    ..:: “Every day, 20 MILLION TONS of that CO2 are absorbed into the OCEANS, thereby increasing the overall ACIDITY of the OCEANS.

    By 2100, Ocean acidity will increase another 150 to 200 hundred percent.

    This is a dramatic change in the acidity of the oceans. And it has a serious impact on our ocean ecosystems; in particular, it has an impact on any species of calcifying organism that produces a calcium carbonate SHELL.

    ..:: “These are changes that are occurring far too fast for the oceans to correct naturally, said Dr Richard Feely with the US National Oceanic and Atmospheric Administration (NOAA)

    ..:: “Fifty-five million years ago when we had an event like this (and that took over 10,000 years to occur), it took the oceans over 125,000 years to recover, just to get the chemistry back to normal,” he told BBC News.

    ..:: “It took two to 10 million years for the organisms to re-evolve, to get back into a normal situation.

    ..:: “So what we do over the next 100 years will have implications for ocean ecosystems from tens of thousands to millions of years. That’s the implication of what we’re doing to the oceans right now.”

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