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Charles, CD, Rind D, Jouzel J, Koster RD, Fairbanks RG.  1995.  Seasonal Precipitation Timing and Ice Core Records. Science. 269:247-248.   10.1126/science.269.5221.247   AbstractWebsite
Guilderson, TP, Fallon S, Moore MD, Schrag DP, Charles CD.  2009.  Seasonally resolved surface water Delta C-14 variability in the Lombok Strait: A coralline perspective. Journal of Geophysical Research-Oceans. 114   10.1029/2008jc004876   AbstractWebsite

We have explored surface water mixing in the Lombok Strait through a bimonthly resolved surface water Delta C-14 time series reconstructed from a coral in the Lombok Strait that spans 1937 through 1990. The prebomb surface water Delta C-14 average is -60.5 parts per thousand and individual samples range from -72 parts per thousand to 134 parts per thousand. The annual average postbomb maximum occurs in 1973 at 122 parts per thousand The timing of the postbomb maximum is consistent with a primary subtropical source for the surface waters in the Indonesian seas. During the postbomb period, the coral records regular seasonal cycles of 5 parts per thousand to 20 parts per thousand. Seasonal high Delta C-14 occur during March-May (warm, low salinity), and low Delta C-14 occur in September (cool, higher salinity). The Delta C-14 seasonality is coherent and in phase with the seasonal Delta C-14 cycle observed in Makassar Strait. We estimate the influence of high Delta C-14 Makassar Strait (North Pacific) water flowing through the Lombok Strait using a two end-member mixing model and the seasonal extremes observed at the two sites. The percentage of Makassar Strait water varies between 16 parts per thousand and 70 parts per thousand, and between 1955 and 1990, it averages at 40 parts per thousand. The rich Delta C-14 variability has a biennial component reflecting remote equatorial Indian Ocean forcing and a component in the ENSO band, which is interpreted to reflect Pacific forcing on the Delta C-14 signature in Lombok Strait.

Shemesh, A, Hodell D, Crosta X, Kanfoush S, Charles C, Guilderson T.  2002.  Sequence of events during the last deglaciation in Southern Ocean sediments and Antarctic ice cores. Paleoceanography. 17   10.1029/2000pa000599   AbstractWebsite

[1] The last glacial to interglacial transition was studied using down core records of stable isotopes in diatoms and foraminifera as well as surface water temperature, sea ice extent, and ice-rafted debris (IRD) concentrations from a piston core retrieved from the Atlantic sector of the Southern Ocean. Sea ice is the first variable to change during the last deglaciation, followed by nutrient proxies and sea surface temperature. This sequence of events is independent of the age model adopted for the core. The comparison of the marine records to Antarctic ice CO2 variation depends on the age model as C-14 determinations cannot be obtained for the time interval of 29.5-14.5 ka. Assuming a constant sedimentation rate for this interval, our data suggest that sea ice and nutrient changes at about 19 ka B. P. lead the increase in atmospheric pCO(2) by approximately 2000 years. Our diatom-based sea ice record is in phase with the sodium record of the Vostok ice core, which is related to sea ice cover and similarly leads the increase in atmospheric CO2. If gas exchange played a major role in determining glacial to interglacial CO2 variations, then a delay mechanism of a few thousand years is needed to explain the observed sequence of events. Otherwise, the main cause of atmospheric pCO(2) change must be sought elsewhere, rather than in the Southern Ocean.

Stoner, JS, Channell JET, Hodell DA, Charles CD.  2003.  A similar to 580 kyr paleomagnetic record from the sub-Antarctic South Atlantic (Ocean Drilling Program Site 1089). Journal of Geophysical Research-Solid Earth. 108   10.1029/2001jb001390   AbstractWebsite

We report geomagnetic directional paleosecular variation, relative paleointensity proxies and oxygen isotope data from the upper 88 m composite depth (mcd) at South Atlantic Ocean Drilling Program (ODP) Site 1089 (40degrees56.2'S, 9degrees53.64'E, 4620 m water depth). The age model is provided by high-resolution oxygen isotope stratigraphy, augmented by radiocarbon dates from the upper 8 mcd of nearby piston core RC11-83. Mean sedimentation rates at Site 1089 are in the range of 15 to 20 cm/kyr. Two intervals during the Brunhes Chron, at similar to29.6 mcd (similar to190 ka) and at similar to48 mcd (similar to335 ka), have component magnetization directions with positive (reverse polarity) inclination; however, the excursional directions are heavily overprinted by the postexcursional field. Magnetite is the dominant carrier of magnetic remanence, and occurs in the pseudosingle-domain (PSD) grain size. An additional higher-coercivity magnetic carrier, characterized by low unblocking temperatures (<350&DEG;C), is assumed to be authigenic pyrrhotite. A decrease in magnetization intensity down core is mirrored by a reduction in pore water sulfate, indicating diagenetic reduction of magnetite. Despite down-core changes in magnetic mineralogy, normalized intensity records from Site 1089 are comparable with high-resolution paleointensity records from the North Atlantic (e.g., ODP Sites 983 and 984). Sediment properties and sedimentation patterns within the Cape (Site 1089) and Iceland (Sites 983 and 984) Basins are distinctly different at both millennial and orbital timescales and therefore preclude lithologic variability from being the source of this correlation. Variations in normalized intensity from Site 1089 therefore appear to reflect changes in global-scale geomagnetic field intensity.

Mortyn, P, Charles CD, Hodell DA.  2002.  Southern Ocean upper water column structure over the last 140 kyr with emphasis on the glacial terminations. Global and Planetary Change. 34:241-252.   10.1016/s0921-8181(02)00118-2   AbstractWebsite

We use delta(18)0 and delta(13)C isotopic records from both shallow- and deep-dwelling planktonic foraminiferal species to describe the transition of surface water column structure over the last two glacial terminations in the Atlantic sector of the Southern Ocean between 41degreesS-50degreesS. The delta(18)O differences between deep- and shallow-dwelling foraminifera are typically less pronounced before and during a termination than they are following a termination. Additionally, delta(13)C minima occur during terminations that may be linked to changes in thermohaline circulation mode. These observations collectively point toward water column structural changes that vary from relatively unstratified to relatively stratified during the course of a typical climate transition. The data can potentially be explained by southward retreats of surface water masses that previously advanced to the north during a typical glacial (i.e. frontal migration). Some of the delta(18)O phenomena can also be explained by subduction, entrainment, and advection of continental ice meltwater from higher latitudes. In either case, the glacial subantarctic between 41degreesS-50degreesS was less thermally stratified than it is today. (C) 2002 Elsevier Science B.V. All rights reserved.

Linsley, BK, Wu HC, Rixen T, Charles CD, Gordon AL, Moore MD.  2017.  SPCZ zonal events and downstream influence on surface ocean conditions in the Indonesian Throughflow region. Geophysical Research Letters. 44:293-303.   10.1002/2016gl070985   AbstractWebsite

Seasonal surface freshening of the Makassar Strait, the main conduit of the Indonesian Throughflow (ITF), is a key factor controlling the ITF. Here we present a 262year reconstruction of seasonal sea-surface-salinity variability from 1742 to 2004 Common Era by using coral O-18 records from the central Makassar Strait. Our record reveals persistent seasonal freshening and also years with significant truncations of seasonal freshening that correlate exactly with South Pacific Convergence Zone (SPCZ) zonal events >4000km to the east. During these events, the SPCZ dramatically rotates similar to 15 degrees north to near the equator and stronger westward flowing South Pacific boundary currents force higher-salinity water through the Makassar Strait in February-May halting the normal seasonal freshening in the strait. By these teleconnections, our Makassar coral O-18 series provides the first record of the recurrence interval of these zonal SPCZ events and demonstrates that they have occurred on a semiregular basis since the mid-1700s.

Hartmann, AC, Carilli JE, Norris RD, Charles CD, Deheyn DD.  2010.  Stable isotopic records of bleaching and endolithic algae blooms in the skeleton of the boulder forming coral Montastraea faveolata. Coral Reefs. 29:1079-1089.   10.1007/s00338-010-0667-5   AbstractWebsite

Within boulder forming corals, fixation of dissolved inorganic carbon is performed by symbiotic dinoflagellates within the coral tissue and, to a lesser extent, endolithic algae within the coral skeleton. Endolithic algae produce distinctive green bands in the coral skeleton, and their origin may be related to periods of coral bleaching due to complete loss of dinoflagellate symbionts or "paling" in which symbiont populations are patchily reduced in coral tissue. Stable carbon isotopes were analyzed in coral skeletons across a known bleaching event and 12 blooms of endolithic algae to determine whether either of these types of changes in photosynthesis had a clear isotopic signature. Stable carbon isotopes tended to be enriched in the coral skeleton during the initiation of endolith blooms, consistent with enhanced photosynthesis by endoliths. In contrast, there were no consistent delta(13)C patterns directly associated with bleaching, suggesting that there is no unique isotopic signature of bleaching. On the other hand, isotopic values after bleaching were lighter 92% of the time when compared to the bleaching interval. This marked drop in skeletal delta(13)C may reflect increased kinetic fractionation and slow symbiont recolonization for several years after bleaching.

Rafter, PA, Sigman DM, Charles CD, Kaiser J, Haug GH.  2012.  Subsurface tropical Pacific nitrogen isotopic composition of nitrate: Biogeochemical signals and their transport. Global Biogeochemical Cycles. 26   10.1029/2010gb003979   AbstractWebsite

We report measurements of the nitrogen isotopic composition of nitrate (the delta(15)N of NO(3)(-)) across the equatorial Pacific, for zonal transects from 165 degrees E to 95 degrees W and meridional transects across 95 degrees and 110 degrees W. The delta(15)N of NO(3)(-) is similar in the equatorial thermocline (approximate to 100 m) and intermediate depth waters (approximate to 150 to 600 m), averaging (7.1 +/- 0.3)parts per thousand and (7.1 +/- 0.1)parts per thousand, respectively. These values are more than 2 parts per thousand higher than subthermocline waters of the Southern and Atlantic Oceans and are approximate to 1 parts per thousand higher than putative source waters in the high latitude South Pacific (Subantarctic Mode Water, SAMW). The combined constraints of nitrate concentration and delta(15)N of NO(3)(-) in the equatorial Pacific require (1) lateral exchange between the high-latitude source waters and the zones of denitrification in the eastern tropical Pacific and (2) the accumulation of remineralized nutrients at depth. The zonal uniformity of the subsurface equatorial Pacific delta(15)N of NO(3)(-) indicates rapid transport within the equatorial zone, which works to homogenize the delta(15)N of NO(3)(-) across the Pacific basin. Against this backdrop of high delta(15)N of NO(3)(-) in the tropical Pacific, we find a discrete off-equatorial core of lower delta(15)N of NO(3)(-) (5.5 +/- 0.3)parts per thousand concentrated at 5 degrees S and 150 to 200 m along the 110 degrees and 95 degrees W transects and in apparent association with the Southern Subsurface Counter Current (SSCC). We propose that the remineralized products of nitrogen fixation, at the source of the SSCC in the western south Pacific, are the origin of the low delta(15)N of NO(3)(-) in these waters.