@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 {2619,
	title = {An atmospheric chronology for the glacial-deglacial Eastern Equatorial Pacific},
	journal = {Nature Communications},
	volume = {9},
	year = {2018},
	month = {Aug-06-2018},
	abstract = {Paleoclimate reconstructions are only as good as their chronology. In particular, different chronological assumptions for marine sediment
cores can lead to different reconstructions of ocean ventilation age and atmosphere-ocean carbon exchange history. Here we build the first high-resolution chronology that is free of the dating uncertainties common in marine sediment records, based on radiocarbon dating twigs found with computed tomography scans in two cores from the Eastern Equatorial Pacific (EEP). With this accurate chronology, we show that the ventilation ages of the EEP thermocline and intermediate waters were similar to today during the Last Glacial Maximum and deglaciation, in contradiction with previous studies. Our results suggest that the glacial respired carbon pool in the EEP was not significantly older than today, and that the deglacial strengthening of the equatorial Pacific carbon source was probably driven by low-latitude processes rather than an increased subsurface supply of upwelled carbon from high-latitude oceans.},
	doi = {10.1038/s41467-018-05574-x},
	url = {http://www.nature.com/articles/s41467-018-05574-xhttp://www.nature.com/articles/s41467-018-05574-x.pdfhttp://www.nature.com/articles/s41467-018-05574-xhttp://www.nature.com/articles/s41467-018-05574-x.pdf},
	author = {Zhao, Ning and Keigwin, Lloyd D.}
}
@article {2824,
	title = {Last Glacial Maximum surface water properties and circulation over Laurentian Fan, western North Atlantic},
	journal = {Earth and Planetary Science Letters},
	volume = {500},
	year = {2018},
	month = {Jan-10-2018},
	pages = {47 - 55},
	abstract = {Millennial scale events marked by the contribution of detrital sand are recorded in North Atlantic sediments during the Last Glacial Maximum (LGM), between Heinrich events (HE) 1 and 2, and left their imprint on Laurentian Fan (LF {\textendash} 43{\textdegree}N) sediments off eastern Canada. The LF counterpart of the well-known detrital events consist of glacial red-brick sediments resulting from subglacial flows separated by olive-grey sediments appears at \~{}21.4{\textendash}19.9 and \~{}19.5{\textendash}18.65 cal kyr BP. High-resolution analyses of diatom assemblages and lithic grains coupled with planktonic oxygen isotopic records reveal that while the red sediment is almost barren of diatoms, foraminifera and lithics (>150 μm), they are abundant in the olive-grey sediment. Diatom assemblages reveal three phases during these events: (1) initial relatively warm/temperate conditions followed by (2) very cold surface water and drifting ice, and (3) a final phase characterized by relatively warmer waters and the appearance of detrital carbonate. Although these events possibly reflect the variability specific to the slope water region, they are likely the response to Atlantic Meridional Overturning Circulation perturbations and ice-sheet instability. Through a chain of mechanisms, meltwater inputs into the North Atlantic led ultimately to an increased volume of tropical waters and part of the heat stored in the subsurface was flushed by a brief convective episode that was not sustained, accounting for the return of cold conditions after the events. The sequence of mechanisms deduced from the paleo data here and elsewhere is consistent with previous modeling results. These data suggest that the detrital events between Heinrich event 1 and 2 may be synchronous across the North Atlantic, and that the LGM was probably not a time of prolonged steady state in the climate system.},
	keywords = {detrital events, diatoms, ice rafted debris, Last glacial maximum, Laurentide ice sheet, subglacial flows},
	issn = {0012821X},
	doi = {10.1016/j.epsl.2018.07.038},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0012821X18304448},
	author = {Gil, Isabelle M. and Keigwin, Lloyd D.}
}
@article {2742,
	title = {Late Holocene paleoceanography in the Chukchi and Beaufort Seas, Arctic Ocean, based on benthic foraminifera and ostracodes},
	journal = {arktos},
	volume = {4},
	year = {2018},
	month = {Jan-12-2018},
	abstract = {Calcareous microfossil assemblages in late Holocene sediments from the western Arctic continental shelf provide an important baseline for evaluating the impacts of today{\textquoteright}s changing Arctic oceanography. This study compares 14C-dated late Holocene microfaunal assemblages of sediment cores SWERUS-L2-2-PC1, 2-MC4 and 2-KL1 (57 mwd), which record the last 4200 years in the Herald Canyon (Chukchi Sea shelf), and HLY1302-JPC-32, GGC-30, MC-29 (60 mwd), which record the last 3000 years in the Beaufort Sea shelf off the coast of Canada. Foraminiferal and ostracode assemblages are typical of Arctic continental shelf environments with annual sea-ice cover and show relatively small changes in terms of variability of dominant species. Important microfaunal changes in the Beaufort site include a spike in Spiroplectammina biformis coinciding with a decrease in Cassidulina reniforme in the last few centuries suggesting an increase of Pacific Water influence and decreased sea-ice. There is low-amplitude centennial-scale variability in proportions of benthic foraminiferal species, such as C. reniforme. In addition to these species, Cassidulina teretis s.l., Elphidium excavatum clavatum and Stainforthia feylingi are also common at this site. At the Herald Canyon site in the last few centuries, C. reniforme peaks around 150 years BP and then decreases while Spiroplectammina earlandi spikes and Acanthocythereis dunelmensis decreases also suggesting an increase in Pacific Water influence and decreased sea-ice at this site. This site also includes Buccella spp. and Elphidium excavatum clavatum. Differences in benthic foraminifera and ostracode species dominance between the two sites may be due to a greater influence of Pacific Water in the Chukchi shelf, compared to the more distal Beaufort shelf, which is also affected by the Beaufort Gyre and the Mackenzie River.},
	issn = {2364-9453},
	doi = {10.1007/s41063-018-0058-7},
	url = {https://link.springer.com/article/10.1007/s41063-018-0058-7},
	author = {Seidenstein, Julia L. and Cronin, Thomas M. and Gemery, Laura and Keigwin, Lloyd D. and Pearce, Christof and Jakobsson, Martin and Coxall, Helen K. and Wei, Emily A. and Driscoll, Neal W.}
}
@article {2486,
	title = {Carbon isotope evidence for a northern source of deep water in the glacial western North Atlantic},
	journal = {Proceedings of the National Academy of Sciences},
	volume = {114},
	year = {2017},
	month = {Feb-03-2018},
	pages = {2831 - 2835},
	abstract = {The prevailing view of western Atlantic hydrography during the Last Glacial Maximum (LGM) calls for transport and intermixing of deep southern and intermediate northern end members. However, δ13C and Δ14C results on foraminifera from a sediment core at 5.0 km in the northern subtropics show that there may have also been a northern source of relatively young, very dense, nutrient-depleted water during the LGM (18 ky to 21 ky ago). These results, when integrated with data from other western North Atlantic locations, indicate that the ocean was poorly ventilated at 4.2 km, with better ventilation above and below that depth. If this is a signal of water mass source and not nutrient storage, it would indicate that a previously unrecognized deep water end member originated along the western margin of the Labrador Sea, analogous to dense water formation today around Antarctica and in the Okhotsk Sea.},
	keywords = {carbon isotopes, Last glacial maximum, ocean ventilation, oxygen isotopes, western north atlantic},
	issn = {0027-8424},
	doi = {10.1073/pnas.1614693114},
	url = {http://www.pnas.org/lookup/doi/10.1073/pnas.1614693114https://syndication.highwire.org/content/doi/10.1073/pnas.1614693114http://www.pnas.org/syndication/doi/10.1073/pnas.1614693114},
	author = {Keigwin, Lloyd D. and Swift, Stephen A.}
}
@article {26,
	title = {Sediment flux and recent paleoclimate in JordanBasin, Gulf of Maine},
	journal = {Continental Shelf Research},
	volume = {96},
	year = {2015},
	note = {PT: J; TC: 0; UT: WOS:000351249700005},
	pages = {45-55},
	abstract = {We report planktonic foraminiferal fluxes (accumulation rates) and oxygen isotopes (5180) from a nine-month sediment trap deployment, and 8180 from three sediment cores in Jordan Basin, Gulf of Maine. The sediment trap was deployed at 150 m, about halfway to the basin floor, and samples were collected every three weeks between August 2010 and May 2011. The planktonic foraminiferal fauna in the trap is dominated by Neogloboquadrina incompta that reached a maximum flux in the second half of October. Oxygen isotope ratios on that species indicate that on average during the collecting period it lived in the surface mixed layer, when compared to predicted values based on data from a nearby hydrographic buoy from the same period. New large diameter piston cores from Jordan Basin are 25 and 28 m long. Marine hemipelagic sediments are 25 m thick, and the sharp contact with underlying red deglacial sediments is bracketed by two radiocarbon dates on bivalves that indicate ice-free conditions began 16,900 calibrated years ago. Radiocarbon dating of foraminifera indicates that the basin floor sediments (270-290 m) accumulated at > 3 m/kyr during the Holocene, whereas rates were about one tenth that on the basin slope (230 m). In principle, Jordan Basin sediments have the potential to provide time series with interannual resolution. Our results indicate the Holocene is marked by similar to 2 degrees C variability in SST, and the coldest events of the 20th century, during the mid 1960s and mid 1920s, appear to be recorded in the uppermost 50 cm of the seafloor. (C) 2015 Elsevier Ltd. All rights reserved.},
	issn = {0278-4343},
	doi = {10.1016/j.csr.2015.01.008},
	author = {Keigwin, Lloyd D. and Pilskaln, Cynthia H.}
}
@article {2546,
	title = {Transient stratification as the cause of the North Pacific productivity spike during deglaciation},
	journal = {Nature Geoscience},
	volume = {6},
	year = {2013},
	month = {Feb-07-2014},
	pages = {622 - 626},
	abstract = {During the B{\o}lling{\textendash}Aller{\o}d warm period of the last deglaciation, about 14 kyr ago, there was a strong and pervasive spike in primary productivity in the North Pacific Ocean1. It has been suggested that this productivity event was caused by an influx of the micronutrient iron from surrounding continental shelves as they were flooded by sea-level rise2. Here we test this hypothesis by comparing numerous proxies of productivity with iron flux and provenance measured from a core from the subarctic Pacific Ocean. We find no evidence for an abrupt deglacial pulse of iron from any source at the time of peak productivity. Instead, we argue that the deglacial productivity peak was caused by two stepwise events. First, deep convection during early deglaciation increased nutrient supply to the surface but also increased the depth of the mixed layer, which pushed surface production deeper in the water column and induced light limitation. A subsequent input of meltwater from northern American ice sheets then stratified the water column, which relieved light limitation while leaving the surface waters enriched in nutrients. We conclude that iron plays, at most, a secondary role in controlling productivity during the glacial and deglacial periods in the subarctic Pacific Ocean.},
	keywords = {Biogeochemistry, Marine biology, Marine chemistry, Palaeoceanography},
	issn = {1752-0894},
	doi = {10.1038/ngeo1873},
	url = {http://www.nature.com/doifinder/10.1038/ngeo1873},
	author = {Lam, Phoebe J. and Robinson, Laura F. and Blusztajn, Jerzy and Li, Camille and Cook, Mea S. and McManus, Jerry F. and Keigwin, Lloyd D.}
}
