scholarly journals A Short Note on Marine Reservoir Age Simulations Used in IntCal20

Radiocarbon ◽  
2020 ◽  
Vol 62 (4) ◽  
pp. 865-871 ◽  
Author(s):  
Martin Butzin ◽  
Timothy J Heaton ◽  
Peter Köhler ◽  
Gerrit Lohmann
Keyword(s):  
General Circulation ◽  
Short Note ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Continental Margins ◽  
Planktic Foraminifera ◽  
Marginal Seas ◽  
Combining Data ◽  
Resolution Model ◽  
Reservoir Age

ABSTRACTBeyond ~13.9 cal kBP, the IntCal20 radiocarbon (14C) calibration curve is based upon combining data across a range of different archives including corals and planktic foraminifera. In order to reliably incorporate such marine data into an atmospheric curve, we need to resolve these records into their constituent atmospheric signal and marine reservoir age. We present results of marine reservoir age simulations enabling this resolution, applying the LSG ocean general circulation model forced with various climatic background conditions and with atmospheric radiocarbon changes according to the Hulu Cave speleothem record. Simulating the spatiotemporal evolution of reservoir ages between 54,000 and 10,700 cal BP, we find reservoir ages between 500 and 1400 yr in the low- and mid-latitudes, but also more than 3000 yr in the polar seas. Our results are broadly in agreement with available marine radiocarbon reconstructions, with the caveat that continental margins, marginal seas, or tropical lagoons are not properly resolved in our coarse-resolution model.

scholarly journals The Challenge of Using Future SWOT Data for Oceanic Field Reconstruction

2016 ◽  
Vol 33 (1) ◽  
pp. 119-126 ◽  
Author(s):  
Lucile Gaultier ◽  
Clément Ubelmann ◽  
Lee-Lueng Fu
Keyword(s):  
High Resolution ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Two Dimensional ◽  
Satellite Mission ◽  
The Future ◽  
Resolution Model ◽  
Mapping Techniques ◽  
Ocean Topography

AbstractConventional altimetry measures a one-dimensional profile of sea surface height (SSH) along the satellite track. Two-dimensional SSH can be reconstructed using mapping techniques; however, the spatial resolution is quite coarse even when data from several altimeters are analyzed. A new satellite mission based on radar interferometry is scheduled to be launched in 2020. This mission, called Surface Water and Ocean Topography (SWOT), will measure SSH at high resolution along a wide swath, thus providing two-dimensional images of the ocean surface topography. This new capability will provide a large amount of data even though they are contaminated with instrument noise and geophysical errors. This paper presents a tool that simulates synthetic observations of SSH from the future SWOT mission using SSH from any ocean general circulation model (OGCM). SWOT-like data have been generated from a high-resolution model and analyzed to investigate the sampling and accuracy characteristics of the future SWOT data. This tool will help explore new ideas and methods for optimizing the retrieval of information from future SWOT missions.

Statistical approaches and tools for IntCal20

2020 ◽  
Author(s):  
Christopher Bronk Ramsey ◽  
Timothy Heaton ◽  
Maarten Blaauw ◽  
Paul Blackwell ◽  
Paula Reimer ◽  
...  
Keyword(s):  
Calibration Curve ◽  
General Circulation ◽  
Large Scale ◽  
Ice Core ◽  
Short Note ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Cosmogenic Radionuclides ◽  
Statistical Approaches ◽  
First Time

<p>The construction of the new IntCal20 calibration curve was undertaken using a number of new statistical approaches (Heaton et al. 2020), when compared to previous versions.  This was partly due to the nature of some of the new datasets; partly to improve the robustness of the curve; and partly to address particular aspects of radiocarbon within the Earth System such as reservoir effects, incorporation of geological carbon in speleothems, and the uncertainties associated with different timescales.  Here the main approaches taken are summarised with a perspective on their strengths and potential weaknesses.</p><p>In particular, the high-resolution extensions to the Hulu speleothem radiocarbon record (Cheng et al. 2018) allow it to be used to anchor the chronology for other key records (Suigetsu, Cariaco, and the Pakistan and Iberian Margins), providing a coherence in the timescale not possible before.  Further, for the first time, we incorporate time varying marine reservoir ages, constrained by the Hamburg Large Scale Geostrophic Ocean General Circulation Model (LSG OGCM)(Butzin et al. 2020).  In addition, work on the relationship to the Greenland ice core timescales (Adolphi et al. 2018) enables us to make direct comparison between radiocarbon dated records and the ice core timescale and here we report on tools to assist with this.</p><p>Along with the update to the calibration curve itself, the associated tools for calibration, age-depth modelling and Bayesian modelling have also been updated to make best use of the new resolution and characteristics of the curve.  Here we summarise updates to Bacon, Calib and OxCal.</p><p>Heaton, TJ. et al (2020) The IntCal20 approach to radiocarbon calibration curve construction: A new methodology using Bayesian splines and errors-in-variables Radiocarbon: in review.</p><p>Cheng, H. et al. (2018) Atmospheric 14C/12C changes during the last glacial period from Hulu Cave. Science, 362(6420), pp.1293-1297. doi:10.1126/science.aau0747</p><p>Adolphi, F. et al. (2018) Connecting the Greenland ice-core and U/Th timescales via cosmogenic radionuclides: Testing the synchronicity of Dansgaard-Oeschger events. Climate of the Past, 14, pp.1755-1781. doi:10.5194/cp-2018-85</p><p>Butzin, M. et al. (2020) A short note on marine reservoir age simulations used in IntCal20. Radiocarbon: in press.</p>

scholarly journals The South China Sea Throughflow Retrieved from Climatological Data*

2009 ◽  
Vol 39 (3) ◽  
pp. 753-767 ◽  
Author(s):  
Max Yaremchuk ◽  
Julian McCreary ◽  
Zuojun Yu ◽  
Ryo Furue
Keyword(s):  
South China Sea ◽  
General Circulation Model ◽  
South China ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Luzon Strait ◽  
The South China Sea ◽  
China Sea ◽  
Ocean General Circulation

Abstract The salinity distribution in the South China Sea (SCS) has a pronounced subsurface maximum from 150–220 m throughout the year. This feature can only be maintained by the existence of a mean flow through the SCS, consisting of a net inflow of salty North Pacific tropical water through the Luzon Strait and outflow through the Mindoro, Karimata, and Taiwan Straits. Using an inverse modeling approach, the authors show that the magnitude and space–time variations of the SCS thermohaline structure, particularly for the salinity maximum, allow a quantitative estimate of the SCS throughflow and its distribution among the three outflow straits. Results from the inversion are compared with available observations and output from a 50-yr simulation of a highly resolved ocean general circulation model. The annual-mean Luzon Strait transport is found to be 2.4 ± 0.6 Sv (Sv ≡ 106 m3 s−1). This inflow is balanced by the outflows from the Karimata (0.3 ± 0.5 Sv), Mindoro (1.5 ± 0.4), and Taiwan (0.6 ± 0.5 Sv) Straits. Results of the inversion suggest that the Karimata transport tends to be overestimated in numerical models. The Mindoro Strait provides the only passage from the SCS deeper than 100 m, and half of the SCS throughflow (1.2 ± 0.3 Sv) exits the basin below 100 m in the Mindoro Strait, a result that is consistent with a climatological run of a 0.1° global ocean general circulation model.

Towards explaining the Nd paradox using reversible scavenging in an ocean general circulation model

2008 ◽  
Vol 274 (3-4) ◽  
pp. 448-461 ◽  
Author(s):  
Mark Siddall ◽  
Samar Khatiwala ◽  
Tina van de Flierdt ◽  
Kevin Jones ◽  
Steven L. Goldstein ◽  
...  
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Ocean General Circulation

scholarly journals A new mechanism for atmospheric mercury redox chemistry: Implications for the global mercury budget

2017 ◽  
Author(s):  
Hannah M. Horowitz ◽  
Daniel J. Jacob ◽  
Yanxu Zhang ◽  
Theodore S. Dibble ◽  
Franz Slemr ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Wet Deposition ◽  
General Circulation ◽  
Gulf Coast ◽  
Circulation Model ◽  
Redox Chemistry ◽  
Ocean General Circulation Model ◽  
Atmospheric Mercury ◽  
Water Soluble ◽  
Second Stage

Abstract. Mercury (Hg) is emitted to the atmosphere mainly as volatile elemental Hg0. Oxidation to water-soluble HgII controls Hg deposition to ecosystems. Here we implement a new mechanism for atmospheric Hg0 / HgII redox chemistry in the GEOS-Chem global model and examine the implications for the global atmospheric Hg budget and deposition patterns. Our simulation includes a new coupling of GEOS-Chem to an ocean general circulation model (MITgcm), enabling a global 3-D representation of atmosphere-ocean Hg0 / HgII cycling. We find that atomic bromine (Br) of marine organobromine origin is the main atmospheric Hg0 oxidant, and that second-stage HgBr oxidation is mainly by the NO2 and HO2 radicals. The resulting lifetime of tropospheric Hg0 against oxidation is 2.7 months, shorter than in previous models. Fast HgII atmospheric reduction must occur in order to match the ~ 6-month lifetime of Hg against deposition implied by the observed atmospheric variability of total gaseous mercury (TGM ≡ Hg0 + HgII(g)). We implement this reduction in GEOS-Chem as photolysis of aqueous-phase HgII-organic complexes in aerosols and clouds, resulting in a TGM lifetime of 5.2 months against deposition and matching both mean observed TGM and its variability. Model sensitivity analysis shows that the interhemispheric gradient of TGM, previously used to infer a longer Hg lifetime against deposition, is misleading because southern hemisphere Hg mainly originates from oceanic emissions rather than transport from the northern hemisphere. The model reproduces the observed seasonal TGM variation at northern mid-latitudes (maximum in February, minimum in September) driven by chemistry and oceanic evasion, but does not reproduce the lack of seasonality observed at southern hemisphere marine sites. Aircraft observations in the lowermost stratosphere show a strong TGM-ozone relationship indicative of fast Hg0 oxidation, but we show that this relationship provides only a weak test of Hg chemistry because it is also influenced by mixing. The model reproduces observed Hg wet deposition fluxes over North America, Europe, and China, including the maximum over the US Gulf Coast driven by HgBr oxidation by NO2 and HO2. Low Hg wet deposition observed over rural China is attributed to fast HgII reduction in the presence of high organic aerosol concentrations. We find that 80 % of global HgII deposition takes place over the oceans, reflecting the marine origin of Br and low concentrations of marine organics for HgII reduction, and most of HO2 and NO2 for second-stage HgBr oxidation.

scholarly journals Global Modeling of Internal Tides Within an Eddying Ocean General Circulation Model

Oceanography ◽  
2012 ◽  
Vol 25 (2) ◽  
pp. 20-29 ◽  
Author(s):  
Brian Arbic ◽  
James Richman ◽  
Jay Shriver ◽  
Patrick Timko ◽  
Joseph Metzger ◽  
...  
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Internal Tides ◽  
Global Modeling ◽  
Ocean General Circulation
Sign in / Sign up

Export Citation Format

Share Document