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  • Primary production  (4)
  • Climate variability  (3)
  • 1
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    Assessing the uncertainties of model estimates of primary productivity in the tropical Pacific Ocean (2009)
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    Publication Date: 2022-05-25
    Description: Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Marine Systems 76 (2009): 113-133, doi:10.1016/j.jmarsys.2008.05.010.
    Description: Depth-integrated primary productivity (PP) estimates obtained from satellite ocean color based models (SatPPMs) and those generated from biogeochemical ocean general circulation models (BOGCMs) represent a key resource for biogeochemical and ecological studies at global as well as regional scales. Calibration and validation of these PP models are not straightforward, however, and comparative studies show large differences between model estimates. The goal of this paper is to compare PP estimates obtained from 30 different models (21 SatPPMs and 9 BOGCMs) to a tropical Pacific PP database consisting of ~1000 14C measurements spanning more than a decade (1983- 1996). Primary findings include: skill varied significantly between models, but performance was not a function of model complexity or type (i.e. SatPPM vs. BOGCM); nearly all models underestimated the observed variance of PP, specifically yielding too few low PP (〈 0.2 gC m-2d-2) values; more than half of the total root-mean-squared model-data differences associated with the satellite-based PP models might be accounted for by uncertainties in the input variables and/or the PP data; and the tropical Pacific database captures a broad scale shift from low biomass-normalized productivity in the 1980s to higher biomass-normalized productivity in the 1990s, which was not successfully captured by any of the models. This latter result suggests that interdecadal and global changes will be a significant challenge for both SatPPMs and BOGCMs. Finally, average root-mean-squared differences between in situ PP data on the equator at 140°W and PP estimates from the satellite-based productivity models were 58% lower than analogous values computed in a previous PP model comparison six years ago. The success of these types of comparison exercises is illustrated by the continual modification and improvement of the participating models and the resulting increase in model skill.
    Description: This research was supported by a grant from the National Aeronautics and Space Agency Ocean Biology and Biogeochemistry program (NNG06GA03G), as well as by numerous other grants to the various participating investigators
    Keywords: Primary production ; Modeling ; Remote sensing ; Satellite ocean color ; Statistical analysis ; Tropical Pacific Ocean (15°N to 15°S and 125°E to 95°W)
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 2
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    Evaluating triple oxygen isotope estimates of gross primary production at the Hawaii Ocean Time-series and Bermuda Atlantic Time-series Study sites (2012)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 117 (2012): C05012, doi:10.1029/2010JC006856.
    Description: The triple oxygen isotopic composition of dissolved oxygen (17Δ) is a promising tracer of gross oxygen productivity (P) in the ocean. Recent studies have inferred a high and variable ratio of P to 14C net primary productivity (12–24 h incubations) (e.g., P:NPP(14C) of 5–10) using the 17Δ tracer method, which implies a very low efficiency of phytoplankton growth rates relative to gross photosynthetic rates. We added oxygen isotopes to a one-dimensional mixed layer model to assess the role of physical dynamics in potentially biasing estimates of P using the 17Δ tracer method at the Bermuda Atlantic Time-series Study (BATS) and Hawaii Ocean Time-series (HOT). Model results were compared to multiyear observations at each site. Entrainment of high 17Δ thermocline water into the mixed layer was the largest source of error in estimating P from mixed layer 17Δ. At both BATS and HOT, entrainment bias was significant throughout the year and resulted in an annually averaged overestimate of mixed layer P of 60 to 80%. When the entrainment bias is corrected for, P calculated from observed 17Δ and 14C productivity incubations results in a gross:net productivity ratio of 2.6 (+0.9 −0.8) at BATS. At HOT a gross:net ratio decreasing linearly from 3.0 (+1.0 −0.8) at the surface to 1.4 (+0.6 −0.6) at depth best reproduced observations. In the seasonal thermocline at BATS, however, a significantly higher gross:net ratio or large lateral fluxes of 17Δ must be invoked to explain 17Δ field observations.
    Description: We acknowledge support from Center for Microbial Oceanography Research and Education (CMORE) (NSF EF-0424599) and NOAA Global Carbon Program (NA 100AR4310093). BL thanks the USA-Israel Binational Science Foundation for supporting his project at BATS.
    Description: 2012-11-08
    Keywords: Bermuda Atlantic Time-series ; Hawaii Ocean Time-series ; Primary production ; Triple oxygen isotopes
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    Interannual variability of primary production and dissolved organic nitrogen storage in the North Pacific Subtropical Gyre (2012)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 117 (2012): G03019, doi:10.1029/2011JG001830.
    Description: The upper ocean primary production measurements from the Hawaii Ocean Time series (HOT) at Station ALOHA in the North Pacific Subtropical Gyre showed substantial variability over the last two decades. The annual average primary production varied within a limited range over 1991–1998, significantly increased in 1999–2000 and then gradually decreased afterwards. This variability was investigated using a one-dimensional ecosystem model. The long-term HOT observations were used to constrain the model by prescribing physical forcings and lower boundary conditions and optimizing the model parameters against data using data assimilation. The model reproduced the general interannual pattern in the observed primary production, and mesoscale variability in vertical velocity was identified as a major contributing factor to the interannual variability in the simulation. Several strong upwelling events occurred in 1999, which brought up nitrate at rates several times higher than other years and elevated the model primary production. Our model results suggested a hypothesis for the observed interannual variability pattern of primary production at Station ALOHA: Part of the upwelled nitrate input in 1999 was converted to and accumulated as semilabile dissolved organic nitrogen (DON), and subsequent recycling of this semilabile DON supported enhanced primary productivity for the next several years as the semilabile DON perturbation was gradually removed via export.
    Description: This work was supported in part by the Center for Microbial Oceanography, Research and Education (C-MORE) (NSF EF-0424599), Hawaii Ocean Time series program (NSF OCE09–26766), the Gordon and Betty Moore Foundation, and the Marine Biological Laboratory.
    Description: 2013-03-10
    Keywords: Mesoscale activity ; North Pacific Subtropical Gyre ; Dissolved organic nitrogen ; Interannual variability ; Primary production
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    Separating the influence of temperature, drought, and fire on interannual variability in atmospheric CO2 (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Global Biogeochemical Cycles 28 (2014): 1295–1310, doi:10.1002/2014GB004890.
    Description: The response of the carbon cycle in prognostic Earth system models (ESMs) contributes significant uncertainty to projections of global climate change. Quantifying contributions of known drivers of interannual variability in the growth rate of atmospheric carbon dioxide (CO2) is important for improving the representation of terrestrial ecosystem processes in these ESMs. Several recent studies have identified the temperature dependence of tropical net ecosystem exchange (NEE) as a primary driver of this variability by analyzing a single, globally averaged time series of CO2 anomalies. Here we examined how the temporal evolution of CO2 in different latitude bands may be used to separate contributions from temperature stress, drought stress, and fire emissions to CO2 variability. We developed atmospheric CO2 patterns from each of these mechanisms during 1997–2011 using an atmospheric transport model. NEE responses to temperature, NEE responses to drought, and fire emissions all contributed significantly to CO2 variability in each latitude band, suggesting that no single mechanism was the dominant driver. We found that the sum of drought and fire contributions to CO2 variability exceeded direct NEE responses to temperature in both the Northern and Southern Hemispheres. Additional sensitivity tests revealed that these contributions are masked by temporal and spatial smoothing of CO2 observations. Accounting for fires, the sensitivity of tropical NEE to temperature stress decreased by 25% to 2.9 ± 0.4 Pg C yr−1 K−1. These results underscore the need for accurate attribution of the drivers of CO2 variability prior to using contemporary observations to constrain long-term ESM responses.
    Description: This work was supported by the Department of Energy Office of Science Biological and Environmental Research Division, the National Science Foundation Decadal and Regional Climate Prediction using Earth System Models (EaSM) program (NSF AGS 1048890 and AGS 1048827), and NASA Carbon Cycle Science (NASA NNX11AF96G). G.K.A. acknowledges a NOAA Climate and Global Change postdoctoral fellowship. J.B.M. and E.J.D. thank NOAA's Climate Program Office's Atmospheric Chemistry, Carbon Cycle, and Climate (AC4) program for support
    Keywords: Carbon cycle ; Climate variability ; Drought ; Fire ; Terrestrial ecosystems ; Atmospheric CO2
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
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    Climate forcing for dynamics of dissolved inorganic nutrients at Palmer Station, Antarctica : an interdecadal (1993–2013) analysis (2016)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 121 (2016): 2369–2389, doi:10.1002/2015JG003311.
    Description: We analyzed 20 years (1993–2013) of observations of dissolved inorganic macronutrients (nitrate, N; phosphate, P; and silicate, Si) and chlorophyll a (Chl) at Palmer Station, Antarctica (64.8°S, 64.1°W) to elucidate how large-scale climate and local physical forcing affect the interannual variability in the seasonal phytoplankton bloom and associated drawdown of nutrients. The leading modes of nutrients (N, P, and Si empirical orthogonal functions 1, EOF1) represent overall negative anomalies throughout growing seasons, showing a mixed signal of variability in the initial levels and drawdown thereafter (low-frequency dynamics). The second most common seasonal patterns of nitrate and phosphate (N and P EOF2) capture prolonged drawdown events during December–March, which are correlated to Chl EOF1. Si EOF2 captures a drawdown event during November–December, which is correlated to Chl EOF2. These different drawdown patterns are shaped by different sets of physical and climate forcing mechanisms. N and P drawdown events during December–March are influenced by the winter and spring Southern Annular Mode (SAM) phase, where nutrient utilization is enhanced in a stabilized upper water column as a consequence of SAM-driven winter sea ice and spring wind dynamics. Si drawdown during November–December is influenced by early sea ice retreat, where ice breakup may induce abrupt water column stratification and a subsequent diatom bloom or release of diatom cells from within the sea ice. Our findings underscore that seasonal nutrient dynamics in the coastal WAP are coupled to large-scale climate forcing and related physics, understanding of which may enable improved projections of biogeochemical responses to climate change.
    Description: U.S. National Science Foundation Grant Numbers: OPP-9011927, 9632763, 0217282, 0823101, GEO-PLR 1440435; NASA ROSES Grant Number: NNX14AL86G
    Description: 2017-03-17
    Keywords: Nutrient drawdown ; Phytoplankton bloom ; Climate variability ; Western Antarctic Peninsula ; Palmer LTER ; Biogeochemistry
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Seasonal forcing of summer dissolved inorganic carbon and chlorophyll a on the western shelf of the Antarctic Peninsula (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 115 (2010): C03024, doi:10.1029/2009JC005267.
    Description: The Southern Ocean is a climatically sensitive region that plays an important role in the regional and global modulation of atmospheric CO2. Based on satellite-derived sea ice data, wind and cloudiness estimates from numerical models (National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis), and in situ measurements of surface (0–20 m depth) chlorophyll a (ChlSurf) and dissolved inorganic carbon (DICSurf) concentration, we show sea ice concentration from June to November and spring wind patterns between 1979 and 2006 had a significant influence on midsummer (January) primary productivity and carbonate chemistry for the Western Shelf of the Antarctic Peninsula (WAP, 64°–68°S, 63.4°–73.3°W). In general, strong (〉3.5 m s−1) and persistent (〉2 months) northerly winds during the previous spring were associated with relatively high (monthly mean 〉 2 mg m−3) ChlSurf and low (monthly mean 〈 2 mmol kg−1) salinity-corrected DIC (DICSurf*) during midsummer. The greater ChlSurf accumulation and DICSurf* depletion was attributed to an earlier growing season characterized by decreased spring sea ice cover or nearshore accumulation of phytoplankton in association with sea ice. The impact of these wind-driven mechanisms on ChlSurf and DICSurf* depended on the extent of sea ice area (SIA) during winter. Winter SIA affected phytoplankton blooms by changing the upper mixed layer depth (UMLD) during the subsequent spring and summer (December–January–February). Midsummer DICSurf* was not related to DICSurf* concentration during the previous summer, suggesting an annual replenishment of surface DIC during fall/winter and a relatively stable pool of deep (〉200 m depth) “winter-like” DIC on the WAP.
    Description: This research was supported by NSF OPP grants 0217282 to HWD at the Virginia Institute of Marine Science and 0823101 to HWD at the MBL.
    Keywords: Climate variability ; Antarctica ; Carbonate system
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    The triple oxygen isotope tracer of primary productivity in a dynamic ocean model (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycle 28 (2014): 538–552, doi:10.1002/2013GB004704.
    Description: The triple oxygen isotopic composition of dissolved oxygen (17Δdis) was added to the ocean ecosystem and biogeochemistry component of the Community Earth System Model, version 1.1.1. Model simulations were used to investigate the biological and physical dynamics of 17Δdis and assess its application as a tracer of gross photosynthetic production (gross oxygen production (GOP)) of O2 in the ocean mixed layer. The model reproduced large-scale patterns of 17Δdis found in observational data across diverse biogeographical provinces. Mixed layer model performance was best in the Pacific and had a negative bias in the North Atlantic and a positive bias in the Southern Ocean. Based on model results, the steady state equation commonly used to calculate GOP from tracer values overestimated the globally averaged model GOP by 29%. Vertical entrainment/mixing and the time rate of change of 17Δdis were the two largest sources of bias when applying the steady state method to calculate GOP. Entrainment/mixing resulted in the largest overestimation in midlatitudes and during summer and fall and almost never caused an underestimation of GOP. The tracer time rate of change bias resulted both in underestimation of GOP (e.g., during spring blooms at high latitudes) and overestimation (e.g., during the summer following a bloom). Seasonally, bias was highest in the fall (September-October-November in the Northern Hemisphere, March-April-May in the Southern), overestimating GOP by 62%, globally averaged. Overall, the steady state method was most accurate in equatorial and low-latitude regions where it estimated GOP to within ±10%. Field applicable correction terms are derived for entrainment and mixing that capture 86% of model vertical bias and require only mixed layer depth history and triple oxygen isotope measurements from two depths.
    Description: We acknowledge support from Center for Microbial Oceanography Research and Education (CMORE) (NSF EF-0424599) and NOAA Climate Program Office (NA 100AR4310093).
    Description: 2014-11-23
    Keywords: Primary production ; Triple oxygen isotope ; Photosynthesis ; Gross primary production ; Carbon ; Oxygen
    Repository Name: Woods Hole Open Access Server
    Type: Article
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