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Sutton, AJ, Feely RA, Maenner-Jones S, Musielwicz S, Osborne J, Dietrich C, Monacci N, Cross J, Bott R, Kozyr A, Andersson AJ, Bates NR, Cai WJ, Cronin MF, DeCarlo EH, Hales B, Howden SD, Lee CM, Manzello DP, McPhaden MJ, Melendez M, Mickett JB, Newton JA, Noakes SE, Noh JH, Olafsdottir SR, Salisbury JE, Send U, Trull TW, Vandemark DC, Weller RA.  2019.  Autonomous seawater pCO(2) and pH time series from 40 surface buoys and the emergence of anthropogenic trends. Earth System Science Data. 11:421-439.   10.5194/essd-11-421-2019   AbstractWebsite

Ship-based time series, some now approaching over 3 decades long, are critical climate records that have dramatically improved our ability to characterize natural and anthropogenic drivers of ocean carbon dioxide (CO2) uptake and biogeochemical processes. Advancements in autonomous marine carbon sensors and technologies over the last 2 decades have led to the expansion of observations at fixed time series sites, thereby improving the capability of characterizing sub-seasonal variability in the ocean. Here, we present a data product of 40 individual autonomous moored surface ocean pCO(2) (partial pressure of CO2) time series established between 2004 and 2013, 17 also include autonomous pH measurements. These time series characterize a wide range of surface ocean carbonate conditions in different oceanic (17 sites), coastal (13 sites), and coral reef (10 sites) regimes. A time of trend emergence (ToE) methodology applied to the time series that exhibit well-constrained daily to interannual variability and an estimate of decadal variability indicates that the length of sustained observations necessary to detect statistically significant anthropogenic trends varies by marine environment. The ToE estimates for seawater pCO(2) and pH range from 8 to 15 years at the open ocean sites, 16 to 41 years at the coastal sites, and 9 to 22 years at the coral reef sites. Only two open ocean pCO(2) time series, Woods Hole Oceanographic Institution Hawaii Ocean Time-series Station (WHOTS) in the subtropical North Pacific and Stratus in the South Pacific gyre, have been deployed longer than the estimated trend detection time and, for these, deseasoned monthly means show estimated anthropogenic trends of 1.9 +/- 0.3 and 1.6 +/- 0.3 mu atm yr(-1), respectively. In the future, it is possible that updates to this product will allow for the estimation of anthropogenic trends at more sites; however, the product currently provides a valuable tool in an accessible format for evaluating climatology and natural variability of surface ocean carbonate chemistry in a variety of regions. Data are available at https.//doi. org/10.7289/V5DB8043 and https.// (Sutton et al., 2018).

Koelling, J, Wallace DWR, Send U, Karstensen J.  2017.  Intense oceanic uptake of oxygen during 2014-2015 winter convection in the Labrador Sea. Geophysical Research Letters. 44:7855-7864.   10.1002/2017gl073933   AbstractWebsite

Measurements of near-surface oxygen (O-2) concentrations and mixed layer depth from the K1 mooring in the central Labrador Sea are used to calculate the change in column-integrated (0-1700 m) O-2 content over the deep convection winter 2014/2015. During the mixed layer deepening period, November 2014 to April 2015, the oxygen content increased by 24.3 +/- 3.4 mol m(-2), 40% higher than previous results from winters with weaker convection. By estimating the contribution of respiration and lateral transport on the oxygen budget, the cumulative air-sea gas exchange is derived. The O2 uptake of 29.1 +/- 3.8 mol m(-2), driven by persistent undersaturation (>= 5%) and strong atmospheric forcing, is substantially higher than predicted by standard (nonbubble) gas exchange parameterizations, whereas most bubble-resolving parameterizations predict higher uptake, comparable to our results. Generally large but varying mixed layer depths and strong heat and momentum fluxes make the Labrador Sea an ideal test bed for process studies aimed at improving gas exchange parameterizations.

Sutton, AJ, Sabine CL, Feely RA, Cai WJ, Cronin MF, McPhaden MJ, Morell JM, Newton JA, Noh JH, Olafsdottir SR, Salisbury JE, Send U, Vandemark DC, Weller RA.  2016.  Using present-day observations to detect when anthropogenic change forces surface ocean carbonate chemistry outside preindustrial bounds. Biogeosciences. 13:5065-5083.   10.5194/bg-13-5065-2016   AbstractWebsite

One of the major challenges to assessing the impact of ocean acidification on marine life is detecting and interpreting long-term change in the context of natural variability. This study addresses this need through a global synthesis of monthly pH and aragonite saturation state (Omega(arag)) climatologies for 12 open ocean, coastal, and coral reef locations using 3-hourly moored observations of surface seawater partial pressure of CO2 and pH collected together since as early as 2010. Mooring observations suggest open ocean subtropical and subarctic sites experience present-day surface pH and Omega(arag) conditions outside the bounds of preindustrial variability throughout most, if not all, of the year. In general, coastal mooring sites experience more natural variability and thus, more overlap with preindustrial conditions; however, present-day Omega(arag) conditions surpass biologically relevant thresholds associated with ocean acidification impacts on Mytilus californianus (Omega(arag) < 1.8) and Crassostrea gigas (Omega(arag) < 2.0) larvae in the California Current Ecosystem (CCE) and Mya arenaria larvae in the Gulf of Maine (Omega(arag) < 1.6). At the most variable mooring locations in coastal systems of the CCE, subseasonal conditions approached Omega(arag) = 1. Global and regional models and data syntheses of ship-based observations tended to underestimate seasonal variability compared to mooring observations. Efforts such as this to characterize all patterns of pH and Omega(arag) variability and change at key locations are fundamental to assessing present-day biological impacts of ocean acidification, further improving experimental design to interrogate organism response under real-world conditions, and improving predictive models and vulnerability assessments seeking to quantify the broader impacts of ocean acidification.

Kortzinger, A, Send U, Wallace DWR, Karstensen J, DeGrandpre M.  2008.  Seasonal cycle of O2 and pCO2 in the central Labrador Sea: Atmospheric, biological, and physical implications. Global Biogeochemical Cycles. 22   10.1029/2007gb003029   AbstractWebsite

We present full 2004-2005 seasonal cycles of CO(2) partial pressure (pCO(2)) and dissolved oxygen (O(2)) in surface waters at a time series site in the central Labrador Sea (56.5 degrees N, 52.6 degrees W) and use these data to calculate annual net air-sea fluxes of CO(2) and O(2) as well as atmospheric potential oxygen (APO). The region is characterized by a net CO(2) sink (2.7 +/- 0.8 mol CO(2) m(-2) yr(-1)) that is mediated to a major extent by biological carbon drawdown during spring/summer. During wintertime, surface waters approach equilibrium with atmospheric CO(2). Oxygen changes from marked undersaturation of about 6% during wintertime to strong supersaturation by up to 10% during the spring/summer bloom. Overall, the central Labrador Sea acts as an O(2) sink of 10.0 +/- 3.1 mol m(-2) yr(-1). The combined CO(2) and O(2) sink functions give rise to a sizable APO flux of 13.0 +/- 4.0 mol m(-2) yr(-1) into surface waters of the central Labrador Sea. A mixed layer carbon budget yields a net community production of 4.0 +/- 0.8 mol C m(-2) during the 2005 productive season about one third of which appears to undergo subsurface respiration in a depth range that is reventilated during the following winter. The timing of the spring bloom is discussed and eddies from the West Greenland Current are thought to be associated with the triggering of the bloom. Finally, we use CO(2) and O(2) mixed layer dynamics during the 2005 spring bloom to evaluate a suite of prominent wind speed-dependent parameterizations for the gas transfer coefficient. We find very good agreement with those parameterizations which yield higher transfer coefficients at wind speeds above 10 m s(-1).

Kortzinger, A, Send U, Lampitt RS, Hartman S, Wallace DWR, Karstensen J, Villagarcia MG, Llinas O, DeGrandpre MD.  2008.  The seasonal pCO2 cycle at 49°N/16.5°W in the northeastern Atlantic Ocean and what it tells us about biological productivity. Journal of Geophysical Research-Oceans. 113   10.1029/2007jc004347   AbstractWebsite

A 2-year record of mixed layer measurements of CO(2) partial pressure (pCO(2)), nitrate, and other physical, chemical, and biological parameters at a time series site in the northeast Atlantic Ocean (49 degrees N/16.5 degrees W) is presented. The data show average undersaturation of surface waters with respect to atmospheric CO(2) levels by about 40 +/- 15 mu atm, which gives rise to a perennial CO(2) sink of 3.2 +/- 1.3 mol m(-2) a(-1). The seasonal pCO(2) cycle is characterized by a summer minimum (winter maximum), which is due to the dominance of biological forcing over physical forcing. Our data document a rapid transition from deep mixing to shallow summer stratification. At the onset of shallow stratification, up to one third of the mixed layer net community production during the productive season had already been accomplished. The combination of high prestratification productivity and rapid onset of stratification appears to have caused the observed particle flux peak early in the season. Mixed layer deepening during fall and winter reventilated CO(2) from subsurface respiration of newly exported organic matter, thereby negating more than one third of the carbon drawdown by net community production in the mixed layer. Chemical signatures of both net community production and respiration are indicative of carbon overconsumption, the effects of which may be restricted, though, to the upper ocean. A comparison of the estimated net community production with satellite-based estimates of net primary production shows fundamental discrepancies in the timing of ocean productivity.