You Chen-Feng

No Thumbnail Available
Last Name
You
First Name
Chen-Feng
ORCID

Filters

2010 - 2015 4
3 1
4
Reset filters

Settings

Search Results

Now showing 1 - 4 of 4
  • Article
    Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements
    (John Wiley & Sons, 2013-09-23) Hathorne, Ed C. ; Gagnon, Alexander C. ; Felis, Thomas ; Adkins, Jess F. ; Asami, Ryuji ; Boer, Wim ; Caillon, Nicolas ; Case, David H. ; Cobb, Kim M. ; Douville, Eric ; deMenocal, Peter B. ; Eisenhauer, Anton ; Garbe-Schonberg, Dieter ; Geibert, Walter ; Goldstein, Steven L. ; Hughen, Konrad A. ; Inoue, Mayuri ; Kawahata, Hodaka ; Kolling, Martin ; Cornec, Florence L. ; Linsley, Braddock K. ; McGregor, Helen V. ; Montagna, Paolo ; Nurhati, Intan S. ; Quinn, Terrence M. ; Raddatz, Jacek ; Rebaubier, Helene ; Robinson, Laura F. ; Sadekov, Aleksey ; Sherrell, Robert M. ; Sinclair, Dan ; Tudhope, Alexander W. ; Wei, Gangjian ; Wong, Henri ; Wu, Henry C. ; You, Chen-Feng
    The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.
  • Article
    Ocean circulation and biogeochemistry moderate interannual and decadal surface water pH changes in the Sargasso Sea
    (John Wiley & Sons, 2015-06-25) Goodkin, Nathalie F. ; Wang, Bo-Shian ; You, Chen-Feng ; Hughen, Konrad A. ; Prouty, Nancy G. ; Bates, Nicholas R. ; Doney, Scott C.
    The oceans absorb anthropogenic CO2 from the atmosphere, lowering surface ocean pH, a concern for calcifying marine organisms. The impact of ocean acidification is challenging to predict as each species appears to respond differently and because our knowledge of natural changes to ocean pH is limited in both time and space. Here we reconstruct 222 years of biennial seawater pH variability in the Sargasso Sea from a brain coral, Diploria labyrinthiformis. Using hydrographic data from the Bermuda Atlantic Time-series Study and the coral-derived pH record, we are able to differentiate pH changes due to surface temperature versus those from ocean circulation and biogeochemical changes. We find that ocean pH does not simply reflect atmospheric CO2 trends but rather that circulation/biogeochemical changes account for >90% of pH variability in the Sargasso Sea and more variability in the last century than would be predicted from anthropogenic uptake of CO2 alone.
  • Preprint
    Chemistry of hot springs along the Eastern Lau Spreading Center
    ( 2010-12-08) Mottl, Michael J. ; Seewald, Jeffrey S. ; Wheat, C. Geoffrey ; Tivey, Margaret K. ; Michael, Peter J. ; Proskurowski, Giora ; McCollom, Thomas M. ; Reeves, Eoghan P. ; Sharkey, Jessica ; You, Chen-Feng ; Chan, Lui-Heung ; Pichler, Thomas
    The Eastern Lau Spreading Center (ELSC) is the southernmost part of the back-arc spreading axis in the Lau Basin, west of the Tonga trench and the active Tofua volcanic arc. Over its 397-km length it exhibits large and systematic changes in spreading rate, magmatic/tectonic processes, and proximity to the volcanic arc. In 2005 we collected 81 samples of vent water from six hydrothermal fields along the ELSC. The chemistry of these waters varies both within and between vent fields, in response to changes in substrate composition, temperature and pressure, pH, water/rock ratio, and input from magmatic gases and subducted sediment. Hot-spring temperatures range from 229º to 363ºC at the five northernmost fields, with a general decrease to the south that is reversed at the Mariner field. The southernmost field, Vai Lili, emitted water at up to 334°C in 1989 but had a maximum venting temperature of only 121ºC in 2005, due to waning activity and admixture of bottom seawater into the subseafloor plumbing system. Chloride varies both within fields and from one field to another, from a low of 528 mmol/kg to a high of 656 mmol/kg, and may be enriched by phase separation and/or leaching of Cl from the rock. Concentrations of the soluble elements K, Rb, Cs, and B likewise increase southward as the volcanic substrate becomes more silica-rich, especially on the Valu Fa Ridge. Iodine and δ7Li increase southward, and δ11B decreases as B increases, apparently in response to increased input from subducted sediment as the arc is approached. Species that decrease southward as temperature falls are Si, H2S, Li, Na/Cl, Fe, Mn, and 87Sr/86Sr, whereas pH, alkalinity, Ca, and Sr increase. Oxygen isotopes indicate a higher water/rock ratio in the three systems on Valu Fa Ridge, consistent with higher porosity in more felsic volcanic rocks. Vent waters at the Mariner vent field on the Valu Fa Ridge are significantly hotter, more acid and metal-rich, less saline, and richer in dissolved gases and other volatiles, including H2S, CO2, and F, than the other vent fields, consistent with input of magmatic gases. The large variations in geologic and geophysical parameters produced by back-arc spreading along the ELSC, which exceed those along mid-ocean ridge spreading axes, produce similar large variations in the composition of vent waters, and thus provide new insights into the processes that control the chemistry of submarine hot springs.
  • Article
    Nonhomogeneous seawater Sr isotopic composition in the coastal oceans : a novel tool for tracing water masses and submarine groundwater discharge
    (American Geophysical Union, 2011-05-07) Huang, Kuo-Fang ; You, Chen-Feng ; Chung, Chuan-Hsiung ; Lin, In-Tian
    Here we present high-precision (2σ = ±3 ppm) 87Sr/86Sr measurements in coastal waters, together with salinity, to evaluate water mass mixing and the influence of submarine groundwater discharge (SGD) in coastal waters and marginal seas. Nonhomogeneous Sr isotopic variations in water columns were documented in the Southern Okinawa Trough (SOT), South China Sea, and Kao-ping Canyon (KPC), where seawater 87Sr/86Sr varied up to 70 ppm. Seawater Sr isotopic composition changes only slightly in the upper 200 m of the SOT but was detectable and highly correlated with salinity, indicating a mixing between radiogenic North Pacific Tropical Water (high 87Sr/86Sr and high salinity) at 100–150 m and a less radiogenic component with low 87Sr/86Sr and low salinity at ∼200 m. Vertical profiles of seawater 87Sr/86Sr along the KPC show significant variations, suggesting dynamic mixing affected by continental inputs (i.e., river runoff and SGD) in this region. These results highlight the potential use of seawater Sr isotopes as a powerful tracer for determining mixing ratios and the dynamic mixing of oceanic water masses, especially in coastal and marginal seas.