@article {lu_surface_2023,
	title = {Surface climate signals transmitted rapidly to deep North Atlantic throughout last millennium},
	journal = {Science},
	volume = {382},
	number = {6672},
	year = {2023},
	note = {Publisher: American Association for the Advancement of Science},
	month = {11/2023},
	pages = {834{\textendash}839},
	chapter = {834},
	abstract = {Instrumental observations of subsurface ocean warming imply that ocean heat uptake has slowed 20th-century surface warming. We present high-resolution records from subpolar North Atlantic sediments that are consistent with instrumental observations of surface and deep warming/freshening and in addition reconstruct the surface-deep relation of the last 1200 years. Sites from \textasciitilde1300 meters and deeper suggest an \textasciitilde0.5 degrees celsius cooling across the Medieval Climate Anomaly to Little Ice Age transition that began \textasciitilde1350 {\textpm} 50 common era (CE), whereas surface records suggest asynchronous cooling onset spanning \textasciitilde600 years. These data suggest that ocean circulation integrates surface variability that is transmitted rapidly to depth by the Atlantic Meridional Ocean Circulation, implying that the ocean moderated Earth{\textquoteright}s surface temperature throughout the last millennium as it does today.},
	doi = {10.1126/science.adf1646},
	url = {https://www.science.org/doi/10.1126/science.adf1646},
	author = {Lu, Wanyi and Oppo, Delia W. and Gebbie, Geoffrey and Thornalley, David J. R.}
}
@article {2972,
	title = {Comparing paleo-oxygenation proxies (benthic foraminiferal surface porosity, I/Ca, authigenic uranium) on modern sediments and the glacial Arabian Sea},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {331},
	year = {2022},
	month = {08/2022},
	pages = {69 - 85},
	abstract = {Oceanic oxygen reconstructions of the last glacial period are needed to understand the mechanisms of glacial deep ocean carbon storage and to validate climate model simulations. However, existing bottom-water oxygen (BWO) reconstructions are ambiguous due to limitations of each paleo-BWO proxy. Here we present data on three proxies for BWO: benthic foraminiferal surface porosity, benthic foraminiferal iodine/calcium (I/Ca), and authigenic uranium (aU), from globally distributed core-top samples, and we evaluate the potential advantages and limitations of these BWO proxies on global and regional scales. All three proxies are most sensitive to changes at relatively low BWO concentrations (<\~{}50 {\textmu}mol/kg). Data from globally-distributed core tops confirm that foraminiferal surface porosity is correlated with BWO between 0 and 100 {\textmu}mol/kg. Our analysis further confirms that benthic surface porosity is predominantly controlled directly by BWO rather than other potential functionalities of surface pores such as organic carbon uptake and respiratory CO2 release. Low benthic I/Ca can identify low BWO (<50 {\textmu}mol/kg), whereas higher benthic I/Ca values are not associated with specific BWO, possibly due to additional dependence of I/Ca on temperature, salinity, carbonate ion concentration, or water mass mixing at higher BWO. The relationship between aU and BWO is regionally dependent. In the Arabian Sea, variable aU enrichments occur only within the Oxygen Minimum Zone (OMZ), driven by high export production and organic matter fluxes to the sediment. Finally, we combine foraminiferal surface porosity, I/Ca and aU to generate the first quantitative glacial-Holocene BWO reconstructions using a sediment core taken from within the modern Arabian Sea OMZ. All three proxies consistently suggest BWO < 50 μmol/kg in the shallow Arabian Sea during the last \~{}30 kyr, with relatively higher BWO during the glacial period than the Holocene. A comparison with the benthic carbon isotope gradient proxy (Δδ13C) confirms that Δδ13C over-estimates BWO in low-oxygen settings possibly due to sediment diagenesis impacts. Our study provides new insights on the merits and limitations of these BWO proxies and confirms the importance of multi-proxy reconstructions for more reliable paleo-BWO estimates.

},
	keywords = {13 Climate Action},
	isbn = {0016-7037},
	doi = {10.1016/j.gca.2022.06.001},
	url = {https://www.sciencedirect.com/science/article/pii/S0016703722002666},
	author = {Lu, Wanyi and Wang, Yi and Oppo, Delia W. and Nielsen, Sune G. and Costa, Kassandra M.}
}
@article {2825,
	title = {Glacial{\textendash}interglacial Nd isotope variability of North Atlantic Deep Water modulated by North American ice sheet},
	journal = {Nature Communications},
	volume = {10},
	year = {2019},
	month = {Jan-12-2019},
	abstract = {The Nd isotope composition of seawater has been used to reconstruct past changes in the contribution of different water masses to the deep ocean. In the absence of contrary information, the Nd isotope compositions of endmember water masses are usually assumed constant during the Quaternary. Here we show that the Nd isotope composition of North Atlantic Deep Water (NADW), a major component of the global overturning ocean circulation, was significantly more radiogenic than modern during the Last Glacial Maximum (LGM), and shifted towards modern values during the deglaciation. We propose that weathering contributions of unradiogenic Nd modulated by the North American Ice Sheet dominated the evolution of the NADW Nd isotope endmember. If water mass mixing dominated the distribution of deep glacial Atlantic Nd isotopes, our results would imply a larger fraction of NADW in the deep Atlantic during the LGM and deglaciation than reconstructed with a constant northern endmember.},
	doi = {10.1038/s41467-019-13707-z},
	url = {http://www.nature.com/articles/s41467-019-13707-z},
	author = {Zhao, Ning and Oppo, Delia W. and Huang, Kuo-Fang and Howe, Jacob N. W. and Blusztajn, Jerzy and Keigwin, Lloyd D.}
}
@article {2745,
	title = {Data Constraints on Glacial Atlantic Water Mass Geometry and Properties},
	journal = {Paleoceanography and Paleoclimatology},
	volume = {33},
	year = {2018},
	month = {Mar-09-2020},
	pages = {1013 - 1034},
	abstract = {The chemical composition of benthic foraminifera from marine sediment cores provides information on how glacial subsurface water properties differed from modern, but separating the influence of changes in the origin and end-member properties of subsurface water from changes in flows and mixing is challenging. Spatial gaps in coverage of glacial data add to the uncertainty. Here we present new data from cores collected from the Demerara Rise in the western tropical North Atlantic, including cores from the modern tropical phosphate maximum at Antarctic Intermediate Water (AAIW) depths. The results suggest lower phosphate concentration and higher carbonate saturation state within the phosphate maximum than modern despite similar carbon isotope values, consistent with less accumulation of respired nutrients and carbon, and reduced air-sea gas exchange in source waters to the region. An inversion of new and published glacial data confirms these inferences and further suggests that lower preformed nutrients in AAIW, and partial replacement of this still relatively high-nutrient AAIW with nutrient-depleted, carbonate-rich waters sourced from the region of the modern-day northern subtropics, also contributed to the observed changes. The results suggest that glacial preformed and remineralized phosphate were lower throughout the upper Atlantic, but deep phosphate concentration was higher. The inversion, which relies on the fidelity of the paleoceanographic data, suggests that the partial replacement of North Atlantic sourced deep water by Southern Ocean Water was largely responsible for the apparent deep North Atlantic phosphate increase, rather than greater remineralization.},
	issn = {2572-4517},
	doi = {10.1029/2018PA003408},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2018PA003408},
	author = {Oppo, Delia W. and Gebbie, Geoffrey and Huang, Kuo-Fang and Curry, William B. and Marchitto, Thomas M. and Pietro, Kathryn R.}
}
@article {2584,
	title = {What do benthic ? <sup>13</sup>               C and ? <sup>18</sup>               O data tell us about Atlantic circulation during Heinrich Stadial 1?},
	journal = {Paleoceanography},
	volume = {30},
	year = {2015},
	month = {Jan-04-2015},
	pages = {353 - 368},
	abstract = {Approximately synchronous with the onset of Heinrich Stadial 1 (HS1), δ13C decreased throughout most of the upper (~1000{\textendash}2500 m) Atlantic, and at some deeper North Atlantic sites. This early deglacial δ13C decrease has been alternatively attributed to a reduced fraction of high-δ13C North Atlantic Deep Water (NADW) or to a decrease in the NADW δ13C source value. Here we present new benthic δ18O and δ13C records from three relatively shallow (~1450{\textendash}1650 m) subpolar Northeast Atlantic cores. With published data from other cores, these data form a depth transect (~1200{\textendash}3900 m) in the subpolar Northeast Atlantic. We compare Last Glacial Maximum (LGM) and HS1 data from this transect with data from a depth transect of cores from the Brazil Margin. The largest LGM-to-HS1 decreases in both benthic δ13C and δ18O occurred in upper waters containing the highest NADW fraction during the LGM. We show that the δ13C decrease can be explained entirely by a lower NADW δ13C source value, entirely by a decrease in the proportion of NADW relative to Southern Ocean Water, or by a combination of these mechanisms. However, building on insights from model simulations, we hypothesize that reduced ventilation due to a weakened but still active Atlantic Meridional Overturning Circulation also contributed to the low δ13C values in the upper North Atlantic. We suggest that the benthic δ18O gradients above ~2300 m at both core transects indicate the depth to which heat and North Atlantic deglacial freshwater had mixed into the subsurface ocean by early HS1.},
	doi = {10.1002/2014PA002667},
	url = {http://doi.wiley.com/10.1002/2014PA002667},
	author = {Oppo, Delia W. and Curry, William B. and McManus, Jerry F.}
}
@article {2588,
	title = {Decreased influence of Antarctic intermediate water in the tropical Atlantic during North Atlantic cold events},
	journal = {Earth and Planetary Science Letters},
	volume = {389},
	year = {2014},
	month = {Jan-03-2014},
	pages = {200 - 208},
	abstract = {Antarctic Intermediate Water (AAIW) is a key player in the global ocean circulation, contributing to the upper limb of the Atlantic Meridional Overturning Circulation (AMOC), and influencing interhemispheric heat exchange and the distribution of salinity, nutrients and carbon. However, the deglacial history of AAIW flow into the North Atlantic is controversial. Here we present a multicore-top neodymium isotope calibration, which confirms the ability of unclean foraminifera to faithfully record bottom water neodymium isotopic composition () values in their authigenic coatings. We then present the first foraminifera-based reconstruction of from three sediment cores retrieved from within modern AAIW, in the western tropical North Atlantic. Our records reveal similar glacial and interglacial contributions of AAIW, and a pronounced decrease in the AAIW fraction during North Atlantic deglacial cold episodes, Heinrich Stadial 1 (HS1) and Younger Dryas (YD). Our results suggest two separate phases of reduced fraction of AAIW in the tropical Atlantic during HS1, with a greater reduction during early HS1. If a reduction in AAIW fraction also reflects reduced AMOC strength, this finding may explain why, in many regions, there are two phases of hydrologic change within HS1, and why atmospheric CO2 rose more rapidly during early than late HS1. Our result suggesting less flow of AAIW into the Atlantic during North Atlantic cold events contrasts with evidence from the Pacific, where intermediate-depth records may indicate increased flow of AAIW into the Pacific during the these same events. Antiphased behavior between intermediate depths of the North Atlantic and Pacific implies that the flow of AAIW into Atlantic and Pacific seesawed during the last deglaciation.},
	keywords = {antarctic intermediate water, Atlantic meridional overturning circulation, deglacial variability, Nd isotopes, North Atlantic cold events},
	issn = {0012821X},
	doi = {10.1016/j.epsl.2013.12.037},
	url = {https://doi.org/10.1016/j.epsl.2013.12.037},
	author = {Huang, Kuo-Fang and Oppo, Delia W. and Curry, William B.}
}
@article {2587,
	title = {Deglacial ?18O and hydrologic variability in the tropical Pacific and Indian Oceans},
	journal = {Earth and Planetary Science Letters},
	volume = {387},
	year = {2014},
	month = {Jan-02-2014},
	pages = {240 - 251},
	abstract = {Evidence from geologic archives suggests that there were large changes in the tropical hydrologic cycle associated with the two prominent northern hemisphere deglacial cooling events, Heinrich Stadial 1 (HS1; \~{}19 to 15 kyr BP; kyr BP = 1000 yr before present) and the Younger Dryas (\~{}12.9 to 11.7 kyr BP). These hydrologic shifts have been alternatively attributed to high and low latitude origin. Here, we present a new record of hydrologic variability based on planktic foraminifera-derived δ18O of seawater (δ18Osw) estimates from a sediment core from the tropical Eastern Indian Ocean, and using 12 additional δ18Osw records, construct a single record of the dominant mode of tropical Eastern Equatorial Pacific and Indo-Pacific Warm Pool (IPWP) hydrologic variability. We show that deglacial hydrologic shifts parallel variations in the reconstructed interhemispheric temperature gradient, suggesting a strong response to variations in the Atlantic Meridional Overturning Circulation and the attendant heat redistribution. A transient model simulation of the last deglaciation suggests that hydrologic changes, including a southward shift in the Intertropical Convergence Zone (ITCZ) which likely occurred during these northern hemisphere cold events, coupled with oceanic advection and mixing, resulted in increased salinity in the Indonesian region of the IPWP and the eastern tropical Pacific, which is recorded by the δ18Osw proxy. Based on our observations and modeling results we suggest the interhemispheric temperature gradient directly controls the tropical hydrologic cycle on these time scales, which in turn mediates poleward atmospheric heat transport.},
	keywords = {Deglaciation, Eastern Equatorial Pacific, heat transport, Indo-Pacific, δ18O of seawater},
	issn = {0012821X},
	doi = {10.1016/j.epsl.2013.11.032},
	url = {https://doi.org/10.1016/j.epsl.2013.11.032},
	author = {Gibbons, Fern T. and Oppo, Delia W. and Mohtadi, Mahyar and Rosenthal, Yair and Cheng, Jun and Liu, Zhengyu and Linsley, Braddock K.}
}
@article {2585,
	title = {Indonesian vegetation response to changes in rainfall seasonality over the past 25,000 years},
	journal = {Nature Geoscience},
	volume = {7449278721172063253871891072011563523665412739429544323},
	year = {2014},
	month = {Jan-06-2014},
	pages = {513 - 517},
	abstract = {The hydrologic response to climate forcing in the Indo-Pacific warm pool region has varied spatially over the past 25,000 years1, 2, 3, 4, 5. For example, drier conditions are inferred on Java and Borneo for the period following the end of the Last Glacial Maximum, whereas wetter conditions are reconstructed for northwest Australia4. The response of vegetation to these past rainfall variations is poorly constrained. Using a suite of 30 surface marine sediment samples from throughout the Indo-Pacific warm pool, we demonstrate that today the stable isotopic composition of vascular plant fatty acids (δ13Cfa) reflects the regional vegetation composition. This in turn is controlled by the seasonality of rainfall consistent with dry season water stress6. Applying this proxy in a sediment core from offshore northeast Borneo, we show broadly similar vegetation cover during the Last Glacial Maximum and the Holocene, suggesting that, despite generally drier glacial conditions1, 7, there was no pronounced dry season. In contrast, δ13Cfa and pollen data from a core off the coast of Sumba indicate an expansion of C4 herbs during the most recent glaciation, implying enhanced aridity and water stress during the dry season. Holocene vegetation trends are also consistent with a response to dry season water stress. We therefore conclude that vegetation in tropical monsoon regions is susceptible to increases in water stress arising from an enhanced seasonality of rainfall, as has occurred8 in past decades.},
	keywords = {Palaeoclimate, Palaeoecology},
	issn = {1752-0894},
	doi = {10.1038/ngeo2182},
	url = {http://www.nature.com/doifinder/10.1038/ngeo2182},
	author = {Dubois, Nathalie and Oppo, Delia W. and Galy, Valier V. and Mohtadi, Mahyar and van der Kaars, Sander and Tierney, Jessica E. and Rosenthal, Yair and Eglinton, Timothy I. and L?ckge, Andreas and Linsley, Braddock K.}
}
@article {2586,
	title = {North Atlantic forcing of tropical Indian Ocean climate},
	journal = {Nature},
	volume = {509},
	year = {2014},
	month = {Jun-04-2016},
	pages = {76 - 80},
	abstract = {The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells1, 2, 3, 4, 5, but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well-dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells.},
	keywords = {Palaeoceanography, Palaeoclimate},
	issn = {0028-0836},
	doi = {10.1038/nature13196},
	url = {http://www.nature.com/doifinder/10.1038/nature13196},
	author = {Mohtadi, Mahyar and Prange, Matthias and Oppo, Delia W. and De Pol-Holz, Ricardo and Merkel, Ute and Zhang, Xiao and Steinke, Stephan and {\"u}ckge, Andreas}
}
@article {196,
	title = {Glacial to Holocene swings of the Australian-Indonesian monsoon},
	journal = {Nature Geoscience},
	volume = {4},
	year = {2011},
	note = {id: 2012; PT: J; UT: WOS:000293277100016},
	pages = {540-544},
	abstract = {The Australian-Indonesian monsoon is an important component of the climate system in the tropical Indo-Pacific region(1). However, its past variability, relation with northern and southern high-latitude climate and connection to the other Asian monsoon systems are poorly understood. Here we present high-resolution records of monsoon-controlled austral winter upwelling during the past 22,000 years, based on planktic foraminiferal oxygen isotopes and faunal composition in a sedimentary archive collected offshore southern Java. We show that glacial-interglacial variations in the Australian-Indonesian winter monsoon were in phase with the Indian summer monsoon system, consistent with their modern linkage through cross-equatorial surface winds. Likewise, millennial-scale variability of upwelling shares similar sign and timing with upwelling variability in the Arabian Sea. On the basis of element composition and grain-size distribution as precipitation-sensitive proxies in the same archive, we infer that (austral) summer monsoon rainfall was highest during the Bolling-Allerod period and the past 2,500 years. Our results indicate drier conditions during Heinrich Stadial 1 due to a southward shift of summer rainfall and a relatively weak Hadley cell south of the Equator. We suggest that the Australian-Indonesian summer and winter monsoon variability were closely linked to summer insolation and abrupt climate changes in the northern hemisphere.},
	issn = {1752-0894},
	doi = {10.1038/NGEO1209},
	author = {Mohtadi, Mahyar and Oppo, Delia W. and Steinke, Stephan and Stuut, Jan-Berend W. and De Pol-Holz, Ricardo and Hebbeln, Dierk and Lueckge, Andreas}
}
@article { ISI:000281467500020,
	title = {Holocene evolution of the Indonesian throughflow and the western Pacific warm pool},
	journal = {NATURE GEOSCIENCE},
	volume = {3},
	number = {{8}},
	year = {2010},
	month = {AUG},
	pages = {578-583},
	type = {Article},
	abstract = {High sea surface temperatures in the western Pacific warm pool fuel atmospheric convection and influence tropical climate. This region also hosts the Indonesian throughflow, the network of currents through which surface and thermocline waters are transported from the western equatorial Pacific Ocean into the Indian Ocean. Here we show, using records of the delta O-18 and Mg/Ca of planktonic foraminifera from eight sediment cores, that from about 10,000 to 7,000 years ago, sea surface temperatures in the western sector of the western Pacific warm pool were about 0.5 degrees C higher than during pre-industrial times. We also find that about 9,500 years ago, when the South China and Indonesian seas were connected by rising sea level, surface waters in the Makassar Strait became relatively fresher. We suggest that the permanent reduction of surface salinity initiated the enhanced flow at lower, thermocline depths seen in the modern Indonesian throughflow. However, the uniformly warm sea surface temperatures found upstream and downstream of the Indonesian throughflow indicate that the early Holocene warmth in this region was not directly related to reduced heat transport by the throughflow that may have resulted from surface freshening of the Makassar Strait. Instead, we propose that the elevated temperatures were the result of a westward shift or expansion of the boundaries of the western Pacific warm pool.},
	issn = {1752-0894},
	doi = {10.1038/ngeo920},
	author = {Linsley, Braddock K. and Rosenthal, Yair and Oppo, Delia W.}
}
@article {314,
	title = {Postglacial changes in El Nino and La Nina behavior},
	journal = {Geology},
	volume = {38},
	year = {2010},
	note = {id: 1985; PT: J; UT: WOS:000273346200011},
	pages = {43-46},
	abstract = {Paleoclimate reconstructions suggest distinctive changes in the Ell Nino-Southern Oscillation (ENSO), the dominant mode of tropical climate variability, over the last glacial cycle and throughout the Holocene. However, to the best of our knowledge, no studies provide parallel reconstructions of warm (El Nino) and cold (La Nina) phase variability, thus precluding distinction between variations in ENSO activity and the mean state of the tropical Pacific. Here we provide the first such records, generated using molecular organic geochemical proxies in a sediment core from the Peru margin region. The opposing influences of El Nino and La Nina on coastal upwelling and phytoplankton community structure produce distinct sedimentary sterol records describing the evolution of each ENSO phase. We document changes in surface ocean productivity on the Peru margin over the past 16 ka that indicate enhanced La Nina-like conditions alone during deglaciation, but concomitant increases in both El Nino and La Nina activity during the past 2 ka. We propose that the preponderance of La Nina-like conditions prior to 11.5 ka reflects the influence of waning glacial boundary conditions. By contrast, warm and cold phase covariability during the late Holocene suggests centennial-scale changes in ENSO activity, rather than the Pacific mean state, driven by tropical insolation.},
	issn = {0091-7613},
	doi = {10.1130/G30366.1},
	author = {Makou, Matthew C. and Eglinton, Timothy I. and Oppo, Delia W. and Hughen, Konrad A.}
}
@inbook {1390,
	title = {North Atlantic intermediate depth variability during the Younger Dryas; evidence from benthic foraminiferal Mg/Ca and the GFDL R30 coupled climate model},
	booktitle = {Geophysical Monograph, vol. 173},
	year = {2007},
	note = {id: 857; American Geophysical Union 2005 fall meeting, San Francisco, CA, United States, Dec 5-9, 2005 NSF grants OCE-0096495, ATM-0502428, OCE-0096472, OCE-0220776 and ATM-0501351 References: 72; illus.; Y},
	month = {2007},
	pages = {247-263},
	publisher = {American Geophysical Union},
	organization = {American Geophysical Union},
	address = {Washington},
	keywords = {24, Quaternary geology, Atlantic Ocean, benthic environment, Cenozoic, chemical ratios, Foraminifera, Glaciation, Gulf of Mexico, ice cores, Invertebrata, isotope ratios, isotopes, Little Bahama Bank, Mg/Ca, microfossils, North Atlantic, O-18/O-16, oxygen, paleo-oceanography, paleobathymetry, paleosalinity, paleotemperature, Pleistocene, Protista, Quaternary, Stable isotopes, Straits of Florida, upper, upper Weichselian, Weichselian, Younger Dryas},
	isbn = {9780875904382},
	author = {Came, Rosemarie E. and Curry, William B. and Oppo, Delia W. and Broccoli, Anthony J. and Stouffer, Ronald J. and Lynch-Stieglitz, Jean},
	editor = {Schmittner, Andreas}
}
@article {2179,
	title = {Glacial deep water geometry: South Atlantic Benthic foraminiferal Cd/Ca and delta13C evidence},
	journal = {Paleoceanography},
	volume = {15},
	year = {2000},
	note = {id: 13050883-8305/00/1999PA000436
},
	month = {2000},
	pages = {147-160},
	author = {Oppo, Delia W. and Horowitz, Michael}
}
