@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 {2738, title = {Remobilization of old permafrost carbon to Chukchi Sea sediments during the end of the last deglaciation}, journal = {Global Biogeochemical Cycles}, year = {2018}, month = {Jan-12-2019}, abstract = {Climate warming is expected to destabilize permafrost carbon (PF-C) by thaw-erosion and deepening of the seasonally thawed active layer and thereby promote PF-C mineralization to CO2 and CH4. A similar PF-C remobilization might have contributed to the increase in atmospheric CO2 during deglacial warming after the last glacial maximum. Using carbon isotopes and terrestrial biomarkers (Δ14C, δ13C, and lignin phenols), this study quantifies deposition of terrestrial carbon originating from permafrost in sediments from the Chukchi Sea (core SWERUS-L2-4-PC1). The sediment core reconstructs remobilization of permafrost carbon during the late Aller{\o}d warm period starting at 13,000 cal years before present (BP), the Younger Dryas, and the early Holocene warming until 11,000 cal years BP and compares this period with the late Holocene, from 3,650 years BP until present. Dual-carbon-isotope-based source apportionment demonstrates that Ice Complex Deposit{\textemdash}ice- and carbon-rich permafrost from the late Pleistocene (also referred to as Yedoma){\textemdash}was the dominant source of organic carbon (66 {\textpm} 8\%; mean {\textpm} standard deviation) to sediments during the end of the deglaciation, with fluxes more than twice as high (8.0 {\textpm} 4.6 g{\textperiodcentered}m-2{\textperiodcentered}year-1) as in the late Holocene (3.1 {\textpm} 1.0 g{\textperiodcentered}m-2{\textperiodcentered}year-1). These results are consistent with late deglacial PF-C remobilization observed in a Laptev Sea record, yet in contrast with PF-C sources, which at that location were dominated by active layer material from the Lena River watershed. Release of dormant PF-C from erosion of coastal permafrost during the end of the last deglaciation indicates vulnerability of Ice Complex Deposit in response to future warming and sea level changes.}, keywords = {carbon isotope, climate change feedback, coastal erosion, Deglaciation, past carbon cycling, permafrost}, issn = {0886-6236}, doi = {10.1029/2018GB005969}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2018GB005969https://onlinelibrary.wiley.com/doi/pdf/10.1029/2018GB005969https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1029\%2F2018GB005969https://onlinelibrary.wiley.com/doi/pdf/10.1029/2018GB005969}, author = {Martens, Jannik and Wild, Birgit and Pearce, Christof and Tesi, Tommaso and Andersson, August and Broder, Lisa and O{\textquoteright}Regan, Matt and Jakobsson, Martin and Sk{\"o}ld, Martin and Gemery, Laura and Cronin, Thomas M. and Semiletov, Igor and Dudarev, Oleg V. and Gustafsson, {\"O}rjan} } @article {2740, title = {The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea}, journal = {Climate of the Past}, volume = {13}, year = {2017}, month = {Jan-01-2017}, pages = {303 - 316}, abstract = {The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal kyr BP was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution, combined with the fact that the eruption is relatively well constrained in time using radiocarbon dating of lake sediments and annual layer counts in ice cores, makes it an excellent stratigraphic marker for dating and correlating mid{\textendash}late Holocene sediment and paleoclimate records. This study presents the outcome of a targeted search for the Aniakchak tephra in a marine sediment core from the Arctic Ocean, namely Core SWERUS-L2-2-PC1 (2PC), raised from 57 m water depth in Herald Canyon, western Chukchi Sea. High concentrations of tephra shards, with a geochemical signature matching that of Aniakchak ash, were observed across a more than 1.5 m long sediment sequence. Since the primary input of volcanic ash is through atmospheric transport, and assuming that bioturbation can account for mixing up to ca. 10 cm of the marine sediment deposited at the coring site, the broad signal is interpreted as sustained reworking at the sediment source input. The isochron is therefore placed at the base of the sudden increase in tephra concentrations rather than at the maximum concentration. This interpretation of major reworking is strengthened by analysis of grain size distribution which points to ice rafting as an important secondary transport mechanism of volcanic ash. Combined with radiocarbon dates on mollusks in the same sediment core, the volcanic marker is used to calculate a marine radiocarbon reservoir age offset ΔR = 477 {\textpm} 60 years. This relatively high value may be explained by the major influence of typically "carbon-old" Pacific waters, and it agrees well with recent estimates of ΔR along the northwest Alaskan coast, possibly indicating stable oceanographic conditions during the second half of the Holocene. Our use of a volcanic absolute age marker to obtain the marine reservoir age offset is the first of its kind in the Arctic Ocean and provides an important framework for improving chronologies and correlating marine sediment archives in this region. Core 2PC has a high sediment accumulation rate averaging 200 cm kyr throughout the last 4000 years, and the chronology presented here provides a solid base for high-resolution reconstructions of late Holocene climate and ocean variability in the Chukchi Sea.}, doi = {10.5194/cp-13-303-2017}, url = {https://cp.copernicus.org/articles/13/303/2017/}, author = {Pearce, Christof and Varhelyi, Aron and Wasteg{\r a}rd, Stefan and Muschitiello, Francesco and Barrientos, Natalia and O{\textquoteright}Regan, Matt and Cronin, Thomas M. and Gemery, Laura and Semiletov, Igor and Backman, Jan and Jakobsson, Martin} } @article {2741, title = {The De Long Trough: a newly discovered glacial trough on the East Siberian continental margin}, journal = {Climate of the Past}, volume = {13}, year = {2017}, month = {Jan-01-2017}, pages = {1269 - 1284}, abstract = {Ice sheets extending over parts of the East Siberian continental shelf have been proposed for the last glacial period and during the larger Pleistocene glaciations. The sparse data available over this sector of the Arctic Ocean have left the timing, extent and even existence of these ice sheets largely unresolved. Here we present new geophysical mapping and sediment coring data from the East Siberian shelf and slope collected during the 2014 SWERUS-C3 expedition (SWERUS-C3: Swedish {\textendash} Russian {\textendash} US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions). The multibeam bathymetry and chirp sub-bottom profiles reveal a set of glacial landforms that include grounding zone formations along the outer continental shelf, seaward of which lies a > 65 m thick sequence of glacio-genic debris flows. The glacial landforms are interpreted to lie at the seaward end of a glacial trough {\textendash} the first to be reported on the East Siberian margin, here referred to as the De Long Trough because of its location due north of the De Long Islands. Stratigraphy and dating of sediment cores show that a drape of acoustically laminated sediments covering the glacial deposits is older than \~{} 50 cal kyr BP. This provides direct evidence for extensive glacial activity on the Siberian shelf that predates the Last Glacial Maximum and most likely occurred during the Saalian (Marine Isotope Stage (MIS) 6).}, doi = {10.5194/cp-13-1269-2017}, url = {https://cp.copernicus.org/articles/13/1269/2017/}, author = {O{\textquoteright}Regan, Matt and Backman, Jan and Barrientos, Natalia and Cronin, Thomas M. and Gemery, Laura and Kirchner, Nina and Mayer, Larry A. and Nilsson, Johan and Noormets, Riko and Pearce, Christof and Semiletov, Igor and Stranne, Christian and Jakobsson, Martin} } @article {2739, title = {Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins}, journal = {Climate of the Past}, volume = {13}, year = {2017}, month = {Jan-01-2017}, pages = {1097 - 1110}, abstract = {Deglacial (12.8{\textendash}10.7 ka) sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1) and multicore SWERUS-L2-4-MC1 (4-MC1), and a gravity core from an East Siberian Sea transect, SWERUS-L2-20-GC1 (20-GC1). Cores 4-PC1 and 20-GC were taken at 120 and 115 m of modern water depth, respectively, only a few meters above the global last glacial maximum (LGM; \~{} 24 kiloannum or ka) minimum sea level of \~{} 125{\textendash}130 meters below sea level (m b.s.l.). Using calibrated radiocarbon ages mainly on molluscs for chronology and the ecology of benthic foraminifera and ostracode species to estimate paleodepths, the data reveal a dominance of river-proximal species during the early part of the Younger Dryas event (YD, Greenland Stadial GS-1) followed by a rise in river-intermediate species in the late Younger Dryas or the early Holocene (Preboreal) period. A rapid relative sea level rise beginning at roughly 11.4 to 10.8 ka ( \~{} 400 cm of core depth) is indicated by a sharp faunal change and unconformity or condensed zone of sedimentation. Regional sea level at this time was about 108 m b.s.l. at the 4-PC1 site and 102 m b.s.l. at 20-GC1. Regional sea level near the end of the YD was up to 42{\textendash}47 m lower than predicted by geophysical models corrected for glacio-isostatic adjustment. This discrepancy could be explained by delayed isostatic adjustment caused by a greater volume and/or geographical extent of glacial-age land ice and/or ice shelves in the western Arctic Ocean and adjacent Siberian land areas.}, doi = {10.5194/cp-13-1097-2017}, url = {https://cp.copernicus.org/articles/13/1097/2017/}, author = {Cronin, Thomas M. and O{\textquoteright}Regan, Matt and Pearce, Christof and Gemery, Laura and Toomey, Michael and Semiletov, Igor and Jakobsson, Martin} } @article {140, title = {Central Arctic paleoceanography for the last 50 kyr based on ostracode faunal assemblages}, journal = {Marine Micropaleontology}, volume = {88{\textendash}89}, year = {2012}, note = {id: 2283}, pages = {65-76}, abstract = {The paleoceanography of the central Arctic Ocean was reconstructed for the last 50 kyr (Marine Isotope Stages (MIS) 1{\textendash}3) based on ostracode assemblages from 21 14C-dated sediment cores from the Mendeleev, Lomonosov, and Gakkel Ridges. Arctic sediments deposited during the Holocene interglacial period (MIS 1), the B{\o}lling{\textendash}Aller{\o}d, and larger interstadial Dansgaard{\textendash}Oeschger (DO) events (3{\textendash}4, 8, and 12) contain abundant Cytheropteron spp., Henryhowella asperrima, and Krithe spp. at intermediate/deep-depths (~ 1000 to 3000 m). These assemblages suggest a ventilated deep, Arctic Ocean water mass similar to the modern Arctic Ocean Deep Water (AODW) during these time periods. In contrast, sediment deposited during stadial events corresponding to Heinrich events 1, 2, 3, and 4, (also possibly the Younger Dryas; YD), contain abundant Polycope spp. (60{\textendash}80\%) suggesting a greater influence of the Atlantic Layer (AL) on the Arctic Intermediate Water (AIW) and AODW. Reduced sea-ice during the early Holocene, the last deglacial, and MIS 3 interstadials is indicated by the reoccurrence of Acetabulastoma arcticum, an epipelagic species that is parasitic on sea-ice dwelling amphipods. One hypothesis to explain these oceanographic changes during longer stadial events, particularly within the last glacial period (MIS 2), involves sluggish ocean circulation, thicker sea-ice cover, and a deeper halocline with ocean exchange between Greenland Sea and Arctic Ocean deep-water through the Fram Strait.}, issn = {0377-8398}, doi = {10.1016/j.marmicro.2012.03.004}, url = {http://www.sciencedirect.com/science/article/pii/S0377839812000278}, author = {Poirier, Robert K. and Cronin, Thomas M. and Briggs Jr, William M. and Lockwood, Rowan} } @article {136, title = {Corrigendum to {\textquotedblleft}Timing and duration of North American glacial lake discharges and the Younger Dryas climate reversal{\textquotedblright} [Quaternary Research 75 (2011) 541{\textendash}551]}, journal = {Quaternary Research}, volume = {77}, year = {2012}, note = {id: 2156}, pages = {214}, issn = {0033-5894}, doi = {10.1016/j.yqres.2011.09.008}, url = {http://www.sciencedirect.com/science/article/pii/S0033589411001190}, author = {Rayburn, John A. and Cronin, Thomas M. and Franzi, David A. and Knuepfer, Peter L. K. and Willard, Debra A.} } @article {151, title = {Paleoenvironmental changes on the northeastern and southwestern Black Sea shelves during the Holocene}, journal = {Quaternary International}, volume = {261}, year = {2012}, note = {id: 2123}, pages = {91-104}, abstract = {Four paleoceanographic events are distinguished during the Holocene based on changes in macro- and microfossil assemblages studied from three sediment cores (Ak 521, 522, 2571) from the outer northeast shelf and from core MAR02-45 situated on the southwest shelf of the Black Sea, west to the Bosphorus. The lithology and fossils were previously studied from cores Ak 521 and Ak 522 and MAR02-45. However, high resolution ostracod analyses from the AMS-14C dated core, Ak 2571, allowed for a revision of the taxonomy and paleoecological interpretation of this microfaunal group on the NE shelf. Downcore changes in the relative abundance of the polyhaline ostracods are found to be contemporaneous in all three cores from the NE shelf. As a result, centennial-millennial scale fluctuations of the bottom-water salinity are resolved in the area. A broader scale examination of paleoenvironmental changes between the NE and SW shelves is also made and the surface to bottom salinity gradient is discussed. An uncalibrated radiocarbon based chronology is used throughout this paper to facilitate comparison with the regional chronostratigraphy of marine transgression and regressions in the Black Sea. The calibrated ages corrected for the changes in reservoir age through the Holocene are also provided. The first paleoceanographic event is associated with the pulse of Mediterranean water previously established at about 9.8{\textendash}9.3 ka BP. This event is clearly observed in the SW region but not on the NE shelf due to a hiatus in the longest core, Ak 521. The second event is represented on both the NE and SW shelves as a replacement of brackish benthic fauna and surface phytoplankton with marine ones between 8.4 and 6.9 ka BP, indicating a gradual increase in salinity. The third event is marked by opposing trends in surface and bottom-water salinity changes. On the NE shelf, bottom-water salinity rose to modern values by \~{} 6.5 ka BP and then decreased within the interval \~{}6.4{\textendash}5.3 ka BP as recorded by the ostracod assemblages. On the SW shelf, surface-water salinity reached modern values by 5.6 ka BP and remained constant until present day as inferred from the dinoflagellate cyst assemblages. The fourth event is marked by a recurring increase in bottom-water salinity to modern values indicated by the polyhaline ostracod assemblages at \~{} 5.3 ka BP in the NE region, after which only minor salinity fluctuations are observed.}, issn = {1040-6182}, doi = {10.1016/j.quaint.2011.11.015}, url = {http://www.sciencedirect.com/science/article/pii/S1040618211006550}, author = {Ivanova, Elena V. and Murdmaa, Ivar O. and Karpuk, Maria S. and Schornikov, Eugene I. and Marret, Fabienne and Cronin, Thomas M. and Buynevich, Ilya V. and Platonova, Elena A.} } @article {186, title = {Timing and duration of North American glacial lake discharges and the Younger Dryas climate reversal}, journal = {Quaternary Research}, volume = {75}, year = {2011}, note = {id: 2184}, pages = {541-551}, abstract = {Radiocarbon-dated sediment cores from the Champlain Valley (northeastern USA) contain stratigraphic and micropaleontologic evidence for multiple, high-magnitude, freshwater discharges from North American proglacial lakes to the North Atlantic. Of particular interest are two large, closely spaced outflows that entered the North Atlantic Ocean via the St. Lawrence estuary about 13,200{\textendash}12,900 cal yr BP, near the beginning of the Younger Dryas cold event. We estimate from varve chronology, sedimentation rates and proglacial lake volumes that the duration of the first outflow was less than 1 yr and its discharge was approximately 0.1 Sv (1 Sverdrup = 106 m3 s-1). The second outflow lasted about a century with a sustained discharge sufficient to keep the Champlain Sea relatively fresh for its duration. According to climate models, both outflows may have had sufficient discharge, duration and timing to affect meridional ocean circulation and climate. In this report we compare the proglacial lake discharge record in the Champlain and St. Lawrence valleys to paleoclimate records from Greenland Ice cores and Cariaco Basin and discuss the two-step nature of the inception of the Younger Dryas.}, issn = {0033-5894}, doi = {10.1016/j.yqres.2011.02.004}, url = {http://www.sciencedirect.com/science/article/pii/S003358941100024X}, author = {Rayburn, John A. and Cronin, Thomas M. and Franzi, David A. and Knuepfer, Peter L. K. and Willard, Debra A.} } @article {391, title = {Sea level rise in Tampa Bay}, journal = {Eos, Transactions, American Geophysical Union}, volume = {88}, year = {2007}, note = {id: 1899; References: 14; illus. incl. geol. sketch map Latitude:N272700,N280200 Longitude:W0822200,W0825100Y}, pages = {117-118}, issn = {0096-3941}, doi = {10.1029/2007eo100002}, author = {Cronin, Thomas M. and Edgar, N. Terence and Brooks, Gregg and Hastings, David and Larson, Rebekka and Hine, Albert and Locker, Stanley and Suthard, Beau and Flower, Benjamin and Hollander, David and Wehmiller, John and Willard, Debra A. and Smith, Shannon} }