SHCal13 Southern Hemisphere Calibration, 0–50,000 Years cal BP

The Southern Hemisphere SHCal04 radiocarbon calibration curve has been updated with the addition of new data sets extending measurements to 2145 cal BP and including the ANSTO Younger Dryas Huon pine data set. Outside the range of measured data, the curve is based upon the ern Hemisphere data sets as presented in IntCal13, with an interhemispheric offset averaging 43 ± 23 yr modeled by an autoregressive process to represent the short-term correlations in the offset.

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High-Precision 14C Measurement of Irish Oaks to Show the Natural Atmospheric 14C Variations of the AD Time Period

Radiocarbon ◽

10.1017/s0033822200005476 ◽

1983 ◽

Vol 25 (2) ◽

pp. 187-196 ◽

Cited By ~ 17

Author(s):

G W Pearson ◽

M G L Baillie

Keyword(s):

High Precision ◽

Wood Species ◽

Calibration Curve ◽

Scintillation Counting ◽

Data Sets ◽

Short Term ◽

Data Set ◽

Significant Bias ◽

Time Period ◽

Term Variation

The high-precision 14C measurement of bi-decade and decade samples of Irish Oak for the time period AD 50 to 1830 is presented. The samples were taken from dendrochronologically dated Irish Oak providing an absolute chronology for this period. While the natural atmospheric 14C concentration shows cyclic deviations from a constant value, the amplitudes of such deviations vary considerably. Repeated measurement and interlaboratory checks justify a claim to accuracy in the data given. Comparison of a large number of data sets between Belfast and Seattle show that the different techniques of scintillation counting of 14C6H6 and gas counting of 14CO2 derived from different wood species grown in different continents give no significant bias. Thus, it is justifiable to use this data set as a high-precision calibration curve for the AD period. Over most of this period bi-decade samples were measured giving a slightly reduced resolution of short-term variation when compared to the measurement of decade intervals; however, any difference is not apparent when such curves are compared. It is of much greater importance that a comparison of data sets is without bias if a combined calibration curve is to have sufficient integrity for general use. Averaging the data from Belfast and Seattle would improve the validity of such an AD 14C calibration curve since it would tend to smooth out slight local variations and become internationally more acceptable.

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High-Precision Radiocarbon Measurements of Tree-Ring Dated Wood from New Zealand: 195 Bc–Ad 995

Radiocarbon ◽

10.1017/s0033822200034639 ◽

2011 ◽

Vol 53 (3) ◽

pp. 529-542 ◽

Cited By ~ 24

Author(s):

Alan Hogg ◽

Jonathan Palmer ◽

Gretel Boswijk ◽

Chris Turney

Keyword(s):

New Zealand ◽

Southern Hemisphere ◽

Calibration Curve ◽

Geographic Location ◽

Temporal Variations ◽

Time Interval ◽

Data Sets ◽

Data Set ◽

Data Points ◽

Lagarostrobos Franklinii

The best means for correcting Southern Hemisphere (SH) radiocarbon measurements, which are significantly influenced by temporal variations in the interhemispheric offset, is by the construction of a SH-specific calibration curve from dendrochronologically dated wood. We present here decadal 14C measurements on dendrochronologically secure New Zealand kauri (Agathis australis), covering the period 195 BC–AD 995, extending the range of calibration measurements from New Zealand tree rings to more than 2 millennia.Recently published Tasmanian huon pine (Lagarostrobos franklinii) data for the interval 165 BC to AD 1095 measured at the Center for Accelerator Mass Spectrometry (CAMS) have underestimated standard errors, which need to be re-assessed before the data can be considered for a Southern Hemisphere calibration curve update. The CAMS huon data, unlike the Waikato kauri data presented here, show a significant reduction in the SH offset for the interval AD 775–855. Although these data points are being checked, it is unlikely this represents a temporal geographic location-dependent offset. With re-assessed errors, the huon data set from 165 BC to AD 995 closely matches the new kauri data, with the combined data sets producing a mean interhemispheric offset with IntCal09 of 44 ± 17 yr for the time interval 195 BC–AD 1845. This SH offset is lower than the modeled offset of 55–58 yr used in the construction of SHCal04, and we recommend the lower value be used in future SHCal updates. Although there is an apparent increase in higher frequency events in the SH offset (NZ kauri plus Tasmanian huon) from 200 BC–AD 1000, the reason for this remains unclear.

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SHCal20 Southern Hemisphere Calibration, 0–55,000 Years cal BP

Radiocarbon ◽

10.1017/rdc.2020.59 ◽

2020 ◽

Vol 62 (4) ◽

pp. 759-778 ◽

Cited By ~ 16

Author(s):

Alan G Hogg ◽

Timothy J Heaton ◽

Quan Hua ◽

Jonathan G Palmer ◽

Chris SM Turney ◽

...

Keyword(s):

Southern Hemisphere ◽

Northern Hemisphere ◽

Tree Ring ◽

Calibration Curve ◽

Data Sets ◽

Errors In Variables ◽

Time Intervals ◽

Tree Ring Data ◽

The Mean ◽

Statistical Approaches

ABSTRACTEarly researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 14C yrs older.

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A High-Resolution Radiocarbon Calibration Between 11,700 and 12,400 Calendar Years Bp Derived from 230Th Ages of Corals from Espiritu Santo Island, Vanuatu

Radiocarbon ◽

10.1017/s0033822200019147 ◽

1998 ◽

Vol 40 (3) ◽

pp. 1093-1105 ◽

Cited By ~ 67

Author(s):

G. S. Burr ◽

J. Warren Beck ◽

F. W. Taylor ◽

Jacques Récy ◽

R. Lawrence Edwards ◽

...

Keyword(s):

High Resolution ◽

Younger Dryas ◽

Climatic Changes ◽

Relative Uncertainty ◽

Scale Growth ◽

Data Set ◽

Surface Ocean ◽

Growth Bands ◽

Radiocarbon Calibration ◽

Good Agreement

This paper presents radiocarbon results from a single Diploastrea heliopora coral from Vanuatu that lived during the Younger Dryas climatic episode, between ca. 11,700 and 12,400 calendar yr bp. The specimen has been independently dated with multiple 230Th measurements to permit calibration of the 14C time scale. Growth bands in the coral were used to identify individual years of growth. 14C measurements were made on each year. These values were averaged to achieve decadal resolution for the 14C calibration. The relative uncertainty of the decadal 14C data was below 1% (2σ). The data are in good agreement with the existing dendrochronology and allow for high-resolution calibration for most years. Variations in the fine structure of the 14C time series preserved in this specimen demonstrate sporadic rapid increases in the Δ14C content of the surface ocean and atmosphere. Certain sharp rises in Δ14C are coincident with gaps in coral growth evidenced by several hiatuses. These may be related to rapid climatic changes that occurred during the Younger Dryas. This is the first coral calibration with decadal resolution and the only such data set to extend beyond the dendrochronology-based 14C calibration.

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Revisions and Extension of the Hohenheim Oak and Pine Chronologies: New Evidence About the Timing of the Younger Dryas/Preboreal Transition

Radiocarbon ◽

10.1017/s0033822200019159 ◽

1998 ◽

Vol 40 (3) ◽

pp. 1107-1116 ◽

Cited By ~ 78

Author(s):

Marco Spurk ◽

Michael Friedrich ◽

Jutta Hofmann ◽

Sabine Remmele ◽

Burkhard Frenzel ◽

...

Keyword(s):

Calibration Curve ◽

Younger Dryas ◽

Ice Cores ◽

Early Holocene ◽

Proxy Data ◽

The Past ◽

Varve Chronology ◽

New Evidence ◽

Radiocarbon Calibration

Oak and pine samples housed at the Institute of Botany, University of Hohenheim, are the backbone of the early Holocene part of the radiocarbon calibration curve, published in 1993 (Becker 1993; Kromer and Becker 1993; Stuiver and Becker 1993; Vogel et al. 1993). Since then the chronologies have been revised. The revisions include 1) the discovery of 41 missing years in the oak chronology and 2) a shift of 54 yr for the oldest part back into the past. The oak chronology was also extended with new samples as far back as 10,429 BP (8480 BC). In addition, the formerly tentatively dated pine chronology (Becker 1993) has been rebuilt and shifted to an earlier date. It is now positioned by 14C matching at 11,871-9900 BP (9922–7951 BC) with an uncertainty of ±20 yr (Kromer and Spurk 1998). With these new chronologies the 14C calibration curve can now be corrected, eliminating the discrepancy in the dating of the Younger Dryas/Preboreal transition between the proxy data of the GRIP and GISP ice cores (Johnsen et al. 1992; Taylor et al. 1993), the varve chronology of Lake Gościąż (Goslar et al. 1995) and the pine chronology (Becker, Kromer and Trimborn 1991).

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Matching Dendrochronological Dates with the Southern Hemisphere 14C Bomb Curve to Confirm Annual Tree Rings in Pseudolmedia rigida from Bolivia

Radiocarbon ◽

10.2458/azu_rc.57.18192 ◽

2015 ◽

Vol 57 (1) ◽

pp. 1-13 ◽

Cited By ~ 14

Author(s):

Laia Andreu-Hayles ◽

Guaciara M Santos ◽

David A Herrera-Ramírez ◽

Javier Martin-Fernández ◽

Daniel Ruiz-Carrascal ◽

...

Keyword(s):

Southern Hemisphere ◽

Tree Rings ◽

Geographic Location ◽

Data Sets ◽

Atmospheric Concentration ◽

Concentration Data ◽

Data Set ◽

Dendrochronological Analysis ◽

Before And After ◽

Ring Analysis

This study used high-precision radiocarbon bomb-pulse dating of selected wood rings to provide an independent validation of the tree growth periodicity of Pseudolmedia rigida (Klotzsch & H. Karst) Cuatrec. from the Moraceae family, collected in the Madidi National Park in Bolivia. 14C content was measured by accelerator mass spectrometry (AMS) in 10 samples from a single tree covering over 70 yr from 1939 to 2011. These preliminary calendar dates were determined by dendrochronological techniques and were also used to select the samples for 14C AMS. In order to validate these preliminary dates using the established Southern Hemisphere (SH) 14C atmospheric concentration data set, the targeted rings were selected to be formed during periods before and after the 14C bomb spike nuclear tests (i.e. 1950s–1960s). The excellent agreement of the dendrochronological dates and the 14C signatures in tree rings associated with the same dates provided by the bomb-pulse 14C atmospheric values for the SH (SHCal zone 1–2) confirms the annual periodicity of the observed growth layers, and thus the high potential of this species for tree-ring analysis. The lack of discrepancies between both data sets also suggests that there are no significant latitudinal differences between the 14C SHCal zone 1–2 curve and the 14C values obtained from the selected tree rings at this geographic location (14°33′S, 68°49′W) in South America. The annual resolution of P. rigida tree rings opens the possibility of broader applications of dendrochronological analysis for ecological and paleoclimatic studies in the Bolivian tropics, as well as the possibility of using wood samples from some tree species from this region to improve the quality of the bomb-pulse 14C SHCal curve at this latitude.

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SCIAMACHY WFM-DOAS XCO<sub>2</sub>: comparison with CarbonTracker XCO<sub>2</sub> focusing on aerosols and thin clouds

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-5-2887-2012 ◽

2012 ◽

Vol 5 (2) ◽

pp. 2887-2931 ◽

Cited By ~ 2

Author(s):

J. Heymann ◽

O. Schneising ◽

M. Reuter ◽

M. Buchwitz ◽

V. V. Rozanov ◽

...

Keyword(s):

Southern Hemisphere ◽

Temporal Correlation ◽

Anthropogenic Activity ◽

Data Sets ◽

Spatial Correlations ◽

Data Set ◽

Cloud Data ◽

Temporal Correlations ◽

Retrieval Errors ◽

The Difference

Abstract. Carbon dioxide (CO2) is the most important greenhouse gas whose atmospheric loading has been significantly increased by anthropogenic activity leading to global warming. Accurate measurements and models are needed in order to reliably predict our future climate. This, however, has challenging requirements. Errors in measurements and models need to be identified and minimised. In this context, we present a comparison between satellite-derived column-averaged dry air mole fractions of CO2, denoted XCO2, retrieved from SCIAMACHY/ENVISAT using the WFM-DOAS algorithm, and output from NOAA's global CO2 modelling and assimilation system CarbonTracker. We investigate to what extent differences between these two data sets are influenced by systematic retrieval errors due to aerosols and unaccounted clouds. We analyse seven years of SCIAMACHY WFM-DOAS version 2.1 retrievals (WFMDv2.1) using the latest version of CarbonTracker (version 2010). We investigate to what extent the difference between SCIAMACHY and CarbonTracker XCO2 are temporally and spatially correlated with global aerosol and cloud data sets. For this purpose, we use a global aerosol data set generated within the European GEMS project, which is based on assimilated MODIS satellite data. For clouds, we use a data set derived from CALIOP/CALIPSO. We find significant correlations of the SCIAMACHY minus CarbonTracker XCO2 difference with thin clouds over the Southern Hemisphere. The maximum temporal correlation we find for Darwin, Australia (r2 = 54%). Large temporal correlations with thin clouds are also observed over other regions of the Southern Hemisphere (e.g. 43% for South America and 31% for South Africa). Over the Northern Hemisphere the temporal correlations are typically much lower. An exception is India, where large temporal correlations with clouds and aerosols have also been found. For all other regions the temporal correlations with aerosol are typically low. For the spatial correlations the picture is less clear. They are typically low for both aerosols and clouds, but dependent on region and season, they may exceed 30% (the maximum value of 46% has been found for Darwin during September to November). Overall we find that the presence of thin clouds can potentially explain a significant fraction of the difference between SCIAMACHY WFMDv2.1 XCO2 and CarbonTracker over the Southern Hemisphere. Aerosols appear to be less of a problem. Our study indicates that the quality of the satellite derived XCO2 will significantly benefit from a reduction of scattering related retrieval errors at least for the Southern Hemisphere.

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An examination of the effect of the TESS extended mission on southern hemisphere monotransits

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936703 ◽

2019 ◽

Vol 631 ◽

pp. A83 ◽

Cited By ~ 4

Author(s):

Benjamin F. Cooke ◽

Don Pollacco ◽

Daniel Bayliss

Keyword(s):

Southern Hemisphere ◽

Large Time ◽

First Year ◽

Data Sets ◽

Data Set ◽

Window Functions ◽

Time Gap ◽

Initial Survey

Context. NASA recently announced an extended mission for TESS. As a result it is expected that the southern ecliptic hemisphere will be re-observed approximately two years after the initial survey. Aims. We aim to explore how TESS re-observing the southern ecliptic hemisphere will impact the number and distribution of monotransits discovered during the first year of observations. This simulation will be able to be scaled to any future TESS re-observations. Methods. We carry out an updated simulation of TESS detections in the southern ecliptic hemisphere. This simulation includes realistic Sector window-functions based on the first 11 sectors of SPOC 2 min SAP lightcurves. We then extend this simulation to cover the expected Year 4 of the mission when TESS will re-observe the southern ecliptic fields. For recovered monotransits we also look at the possibility of predicting the period based on the coverage in the TESS data. Results. We find an updated prediction of 339 monotransits from the TESS Year 1 southern ecliptic hemisphere, and that approximately 80% of these systems (266/339) will transit again in the Year 4 observations. The Year 4 observations will also contribute new monotransits not seen in Year 1, resulting in a total of 149 monotransits from the combined Year 1 and Year 4 data sets. We find that 75% (189/266) of recovered Year 1 monotransits will only transit once in the Year 4 data set. For these systems we will be able to constrain possible periods, but period aliasing due to the large time gap between Year 1 and Year 4 observations means that the true period will remain unknown without further spectroscopic or photometric follow-up.

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Bayesian Evaluation of the Southern Hemisphere Radiocarbon Offset during the Holocene

Radiocarbon ◽

10.1017/s0033822200034226 ◽

2009 ◽

Vol 51 (4) ◽

pp. 1165-1176 ◽

Cited By ~ 17

Author(s):

Alan Hogg ◽

Christopher Bronk Ramsey ◽

Chris Turney ◽

Jonathan Palmer

Keyword(s):

Southern Hemisphere ◽

Northern Hemisphere ◽

Calibration Curve ◽

Early Holocene ◽

Data Sets ◽

Bayesian Calibration ◽

The Holocene ◽

Calibration Program

While an interhemispheric offset in atmospheric radiocarbon levels from AD 1950–950 is now well established, its existence earlier in the Holocene is less clear, with some studies reporting globally uniform 14C levels while others finding Southern Hemisphere samples older by a few decades. In this paper, we present a method for wiggle-matching Southern Hemisphere data sets against Northern Hemisphere curves, using the Bayesian calibration program OxCal 4.1 with the Reservoir Offset function accommodating a potential interhemispheric offset. The accuracy and robustness of this approach is confirmed by wiggle-matching known-calendar age sequences of the Southern Hemisphere calibration curve SHCal04 against the Northern Hemisphere curve IntCal04. We also show that 5 of 9 Holocene Southern Hemisphere data sets are capable of yielding reliable offset information. Those data sets that are accurate and precise show that interhemispheric offset levels in the Early Holocene are similar to modern levels, confirming SHCal04 as the curve of choice for calibrating Southern Hemisphere samples.

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Developing Pseudo Continuous Pedotransfer Functions for International Soils Measured with the Evaporation Method and the HYPROP System: II. The Soil Hydraulic Conductivity Curve

Water ◽

10.3390/w13060878 ◽

2021 ◽

Vol 13 (6) ◽

pp. 878

Author(s):

Amninder Singh ◽

Amir Haghverdi ◽

Hasan Sabri Öztürk ◽

Wolfgang Durner

Keyword(s):

Hydraulic Conductivity ◽

Soil Texture ◽

Measured Data ◽

Pedotransfer Functions ◽

Data Sets ◽

Data Set ◽

Soil Hydraulic Conductivity ◽

Evaporation Method ◽

International Data ◽

Soil Hydraulic

Direct measurement of unsaturated hydraulic parameters is costly and time-consuming. Pedotransfer functions (PTFs) are typically developed to estimate soil hydraulic properties from readily available soil attributes. For the first time, in this study, we developed PTFs to estimate the soil hydraulic conductivity (log(K)) directly from measured data. We adopted the pseudo continuous neural network PTF (PCNN-PTF) approach and assessed its accuracy and reliability using two independent data sets with hydraulic conductivity measured via the evaporation method. The primary data set contained 150 international soils (6963 measured data pairs), and the second dataset consisted of 79 repacked Turkish soil samples (1340 measured data pairs). Four models with different combinations of the input attributes, including soil texture (sand, silt, clay), bulk density (BD), and organic matter content (SOM), were developed. The best performing international (root mean square error, RMSE = 0.520) and local (RMSE = 0.317) PTFs only had soil texture information as inputs when developed and tested using the same data set to estimate log(K). However, adding BD and SOM as input parameters increased the reliability of the international PCNN-PTFs when the Turkish data set was used as the test data set. We observed an overall improvement in the performance of PTFs with the increasing number of data points per soil textural class. The PCNN-PTFs consistently performed high across tension ranges when developed and tested using the international data set. Incorporating the Turkish data set into PTF development substantially improved the accuracy of the PTFs (on average close to 60% reduction in RMSE). Consequently, we recommend integrating local HYPROPTM (Hydraulic Property Analyzer, Meter Group Inc., USA) data sets into the international data set used in this study and retraining the PCNN-PTFs to enhance their performance for that specific region.

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