Atmospheric CO2 and Temperature. What is Normal?

–How much of a change in CO2 concentration and other GHGs is natural? –What is the normal range of CO2 and temperature variability? How is normal defined in this context? –What is the relationship between CO2 and global temperatures

Complex Drilling Logistics for Lake El'gygytgyn, NE Russia

Lake El’gygytgyn was formed by astrophysical chance when a meteorite struck the Earth 100 km north of the Arctic Circle in Chukotka 3.6 Myrs ago (Layer, 2000) on the drainage divide between the Arctic Ocean and the Bering Sea. The crater measures ~18 km in diameter and lies nearly in the center of what was to become Beringia, the largestcontiguous landscape in the Arctic to have escaped continental scale glaciation. Within the crater rim today, Lake El’gygytgyn is 12 km in diameter and 170 m deep, enclosing 350–400 m of sediment deposited since the time of impact (Gebhardt et al., 2006). This setting makes the lake ideal for paleoclimate and impact research

The Age and Origin of the Little Diomede Island Upland Surface

Geomorphology and projected uplift rates indicate that the upland surface of Little Diomede Island may represent a high sea level stand that occurred 2.6 million years ago in the Bering Strait. The 350-363 m upland surface of the island could be correlative with the York terrace, an uplifted marine terrace previously recognized on the southern flanks of the York Mountains, Seward Peninsula. The modern surface of Little Diomede Island is composed of a cryoplanation terrace enclosing a central blockfield and rimmed with tors. Beryllium-l0 cosmogenic isotope analysis of two tors and three outcrops from the upper surface indicate the island has been under the influence of a subaerial periglacial environment at least for the last 36 000 years (MIS 3) and probably for 254 000 (MIS 7/8). Unequivocal evidence does not exist to support glaciation of Little Diomede Island. La géomorphologie et les taux d'exhaussement obtenus par extrapolation révèlent que la surface de haute terre de l'île de Petite Diomède pourrait représenter un relief ayant existé dans le contexte d'un niveau de mer élevé qui avait cours il y a 2,6 millions d'années dans le détroit de Béring. La surface de haute terre de l'île, atteignant de 350 à 363 m, pourrait être en corrélation avec la terrasse de York, terrasse marine surélevée, découverte antérieurement sur les flancs méridionaux des monts York situés dans la péninsule Seward. La surface actuelle de l'île de Petite Diomède se compose d'une terrasse de cryoplanation entourant un champ central de blocs rocheux et circonscrite par des tors. L'analyse isotopique cosmogonique au 10béryllium de deux tors et de trois affleurements de la surface la plus haute révèle que l'île a subi l'influence d'un environnement périglaciaire subaérien pendant au moins les 36 000 dernières années (3e étage isotopique marin) et probablement 254 000 ans (7e/8e étage isotopique marin). On ne possède pas de preuve non équivoque d'une glaciation de l'île de Petite Diomède

Circum-Arctic Late Tertiary/Early Pleistocene Stratigraphy And Environments - A Preface

...During the 1980s the Geological Survey of Canada (GSC) and the U.S. Geological Survey (USGS) initiated a program of joint workshops and cooperative field excursions. The first meeting took place in Calgary, Alberta, in 1984. It dealt with correlation of Quaternary deposits in northwestern North America, but touched on the Tertiary. A second GSC/USGS workshop in early 1987 concerned the Quaternary history of interior basins of Alaska and Canada, but once again the Tertiary became an item of discussion because some of the basins contain a thick sequence of Pliocene and Miocene sediments. It was apparent from the questions that arose at these meetings that there was a need for a dedicated forum on the late Tertiary. The authors organized and convened a workshop with that theme in Denver, Colorado, in October 1987. The papers in this special issue are based on presentations and discussions at that meeting. ..

Oceanographic and Climatic Change in the Bering Sea, Last Glacial Maximum to Holocene

Post‐glacial sea level rise led to a direct connection between the Arctic and Pacific Oceans via the Bering Strait. Consequently, the Bering Sea experienced changes in connectivity, size, and sediment sources that were among the most drastic of any ocean basin in the past 30,000 years. However, the sedimentary response to the interplay between climate change and sea level rise in high‐latitude settings such as Beringia remains poorly resolved. To ascertain changes in sediment delivery, productivity, and regional oceanography from the Last Glacial Maximum (LGM) to the Holocene, we analyzed sedimentological, geochemical, and isotopic characteristics of three sediment cores from the Bering Sea. Interpretations of productivity, terrestrial input, nutrient utilization, and circulation are based on organic carbon isotopes (δ13Corg), total organic carbon (TOC), bulk nitrogen isotopes, total organic nitrogen, carbon/nitrogen ratios, elemental X‐ray fluorescence data, grain size, and presence of laminated or dysoxic, green intervals. Principal component analysis of these data captures key climatic intervals. The LGM was characterized by low productivity across the region. In the Bering Sea, deglaciation began around 18–17 ka, with increasing terrestrial sediment and TOC input. Marine productivity increased during the Bølling‐Allerød when laminated sediments revealed dysoxic bottom waters where denitrification was extreme. The Younger Dryas manifested increased terrestrial input and decreased productivity, in contrast with the Pre‐Boreal, when productivity markedly rebounded. The Pre‐Boreal and Bølling‐Allerød were similarly productive, but changes in the source of TOC and a δ13Corg depletion suggest the influence of a gradually flooding Bering Shelf during the Pre‐Boreal and Holocene

Glacimarine Sedimentation Processes at Kronebreen and Kongsvegen, Svalbard

Tidewater glaciers deposit sediment at their terminus, thereby reducing the relative water depth. Reduced water depth can lead to increased glacier stability through decreased rates of iceberg calving, glacier thinning and submarine melting. Here we investigate sedimentation processes at the termini of Kronebreen and Kongsvegen, Svalbard. We mapped the fjord floor bathymetry in August 2009 and calculate sedimentation rates based on our bathymetry and that from a similar study in 2005. A grounding-line fan is developing near the current position of the subglacial stream. An older, abandoned grounding-line fan that likely formed between ~1987 and 2001 is degrading near the middle of the ice front. Our findings indicate that sediment gravity flows reduce the height of the sediment mound forming at the glacier terminus. The future impact of glacimarine sedimentation processes on glacier stability will depend on the net balance between the observed gravity flows and sediment deposition

Bering Sea Surface Water Conditions during Marine Isotope Stages 12 to 10 at Navarin Canyon (IODP Site U1345)

Records of past warm periods are essential for understanding interglacial climate system dynamics. Marine Isotope Stage 11 occurred from 425 to 394 ka, when global ice volume was the lowest, sea level was the highest, and terrestrial temperatures were the warmest of the last 500 kyr. Because of its extreme character, this interval has been considered an analog for the next century of climate change. The Bering Sea is ideally situated to record how opening or closing of the Pacific–Arctic Ocean gateway (Bering Strait) impacted primary productivity, sea ice, and sediment transport in the past; however, little is known about this region prior to 125 ka. IODP Expedition 323 to the Bering Sea offered the unparalleled opportunity to look in detail at time periods older than had been previously retrieved using gravity and piston cores. Here we present a multi-proxy record for Marine Isotope Stages 12 to 10 from Site U1345, located near the continental shelf-slope break. MIS 11 is bracketed by highly productive laminated intervals that may have been triggered by flooding of the Beringian shelf. Although sea ice is reduced during the early MIS 11 laminations, it remains present at the site throughout both glacials and MIS 11. High summer insolation is associated with higher productivity but colder sea surface temperatures, which implies that productivity was likely driven by increased upwelling. Multiple examples of Pacific–Atlantic teleconnections are presented including laminations deposited at the end of MIS 11 in synchrony with millennial-scale expansions in sea ice in the Bering Sea and stadial events seen in the North Atlantic. When global eustatic sea level was at its peak, a series of anomalous conditions are seen at U1345. We examine whether this is evidence for a reversal of Bering Strait throughflow, an advance of Beringian tidewater glaciers, or a turbidite