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At least 919 records · Page 51Linked to original sources

USGS2006

Estimating Potential Effects of Hypothetical Oil Spills on Polar Bears

Much is known about the transport and fate of oil spilled into the sea and its toxicity to exposed wildlife. Previously, however, there has been no way to quantify the probability that wildlife dispersed over the seascape would be exposed to spilled oil. Polar bears, the apical predator of the arctic, are widely dispersed near the continental shelves of the Arctic Ocean, an area also undergoing considerable hydrocarbon exploration and development. We used 15,308 satellite locations from 194 radiocollared polar bears to estimate the probability that polar bears could be exposed to hypothetical oil spills. We used a true 2 dimensional Gausian kernel density estimator, to estimate the number of bears likely to occur in each 1.00 km2 cell of a grid superimposed over near shore areas surrounding 2 oil production facilities: the existing Northstar oil production facility, and the proposed offshore site for the Liberty production facility. We estimated the standard errors of bear numbers per cell with bootstrapping. Simulated oil spill footprints for September and October, the times during which we hypothesized effects of an oil-spill would be worst, were estimated using real wind and current data collected between 1980 and 1996. We used ARC/Info software to calculate overlap (numbers of bears oiled) between simulated oil-spill footprints and polar bear grid-cell values. Numbers of bears potentially oiled by a hypothetical 5912 barrel spill (the largest spill thought probable from a pipeline breach) ranged from 0 to 27 polar bears for September open water conditions, and from 0 to 74 polar bears in October mixed ice conditions. Median numbers oiled by the 5912 barrel hypothetical spill from the Liberty simulation in September and October were 1 and 3 bears, equivalent values for the Northstar simulation were 3 and 11 bears. In October, 75% of trajectories from the 5912 barrel simulated spill at Liberty oiled 9 or fewer bears while 75% of the trajectories affected 20 or fewer polar bears when we simulated an October spill at the Northstar site. Northstar Island is nearer the active ice flaw zone than Liberty. Simulations suggested that oil spilled at Northstar would spread more effectively and more consistently into surrounding areas. Also, polar bear densities are consistently higher near Northstar. Oil spills simulated for the Liberty site were more erratic in the areas they covered and the numbers of bears impacted, and numbers of bears hypothetically exposed were usually smaller. Methods described here are broadly applicable to other dispersed marine wildlife. Key words: Arctic, Beaufort Sea, clustering, kernel, management, oil spill, polar bears, population delineation, radiotelemetry, satellite, smoothing, Ursus maritimus

Report↗

USGS2007

International Polar Year: Science at the Ends of the Earth

In response to unprecedented changes in the fragile polar regions of our planet, the International Polar Year (IPY) 2007-2008 will encompass many scientific studies designed to improve our understanding of polar change and its effects on Earth's ecosystems and people. For 2 years, U.S. Geological Survey (USGS) researchers will don arctic gear and join scientists from more than 60 countries to conduct coordinated research and analysis in the Arctic and Antarctic. Polar regions play a critical role in the global climate system-and changing conditions in these often remote areas greatly affect biological, atmospheric, and human systems around the world. In the 50 years since the last IPY, scientists have seen that Antarctic ice shelves and glaciers worldwide are thinning and retreating, permafrost is thawing, and Arctic sea-ice cover is decreasing. The loss of sea-ice cover adversely affects marine mammal populations and leaves coastal Alaskan villages vulnerable to winter storm erosion. Thawing permafrost threatens the integrity of roads, buildings, and other vulnerable infrastructure and affects the mobility of local populations.

Fact Sheet↗

USGS2008

Assessment of undiscovered oil and gas resources of the West Greenland-East Canada Province, 2008

The U.S. Geological Survey (USGS) recently assessed the undiscovered oil and gas potential of the West Greenland-East Canada Province as part of the USGS Circum-Arctic Oil and Gas Resource Appraisal effort. The West Greenland-East Canada Province is essentially the offshore area between west Greenland and east Canada and includes Baffin Bay, Davis Strait, Lancaster Sound, and Nares Strait west of and including Kane Basin. The tectonic evolution of the West Greenland-East Canada Province led to the formation of several major structural domains that are the geologic basis for the five assessment units (AU) defined in this study. The five AUs encompass the entire province. Each AU was assessed in its entirety for undiscovered, technically recoverable (assuming absence of sea ice) oil and gas resources, but the assessment results reported here are only for those portions of each AU that are north of the Arctic Circle, as that latitude defines the area of the Circum-Arctic oil and gas assessment.

Baffin Bay, Davis Strait, Kane Basin, Lancaster So↗

USGS2008

Assessment of undiscovered oil and gas resources of the West Siberian Basin Province, Russia, 2008

The U.S. Geological Survey (USGS) recently assessed the undiscovered oil and gas potential of the West Siberian Basin Province in Russia as part of the USGS Circum-Arctic Resource Appraisal program. This province is the largest petroleum basin in the world and has an areal extent of about 2.2 million square kilometers. It is a large rift-sag feature bounded to the west by the Ural fold belt, to the north by the Novaya Zemlya fold belt and North Siberian Sill, to the south by the Turgay Depression and Altay-Sayan fold belt, and to the east by the Yenisey Ridge, Turukhan-Igarka uplift, Yenisey-Khatanga Basin, and Taimyr High. The West Siberian Basin Province has a total discovered oil and gas volume of more than 360 billion barrels of oil equivalent (Ulmishek, 2000). Exploration has led to the discovery of tens of giant oil and gas fields, including the Urengoy gas field with more than 3500 trillion cubic feet of gas reserves and Samotlar oil field with reserves of nearly 28 billion barrels of oil (Ulmishek, 2003). This report summarizes the results of a reassessment of the undiscovered oil and gas potential of that part of the province north of the Arctic Circle; a previous assessment that included the entire province was completed in 2000 (Ulmishek, 2000). The total petroleum system (TPS) and assessment units (AU) defined by the USGS for the assessments in 2000 were adopted for this assessment. However, only those parts of the Aus lying wholly or partially north of the Arctic Circle were assessed for this study.

West Siberian Basin Province↗

USGS2011

A promising tool for subsurface permafrost mapping-An application of airborne geophysics from the Yukon River Basin, Alaska

Permafrost is a predominant physical feature of the Earth's Arctic and Subarctic clines and a major consideration encompassing ecosystem structure to infrastructure engineering and placement. Perennially frozen ground is estimated to cover about 85 percent of the state of Alaska where northern reaches are underlain with continuous permafrost and parts of interior Alaska are underlain by areas of discontinuous and (or) sporadic permafrost (fig. 1). The region of Interior Alaska, where permafrost is scattered among unfrozen ground, is a complex mosaic of terrains and habitats. Such diversity creates arrays of lakes and surface-water and groundwater patterns that continental populations of migratory waterfowl and internationally significant fisheries have adapted to over time. A road or pipeline might pass over frozen and unfrozen ground, affecting the types of materials and engineering approaches needed to sustain the infrastructure. Effective mapping of discontinuous permafrost at scales meaningful ecologically and (or) from an engineering perspective has been a long-standing challenge. Using techniques such as borehole logging for site-specific assessments or botanical techniques that can suggest underlying permafrost distributions can be labor intensive and difficult to accomplish at the scale and remoteness of much of Alaska. The climate is changing in the Arctic and Subarctic regions. The warming observed throughout much of Alaska could create widespread changes in permafrost. How the warming of the permafrost affects near-surface processes, ecosystems, and community infrastructure and ecosystems is not clear. A better understanding of the dynamic distribution and physical properties of permafrost, from continuous to discontinuous, will provide knowledge of how the permafrost environment may change in the future and help inform engineering and natural resource response strategies. Here we discuss an application of an airborne remote sensing methodology for mapping and shade imaging permafrost characteristics at various scales. This work provides the first look into three-dimensional distribution of permafrost in the areas around Fort Yukon and is a demonstration of the application of airborne electromagnetic (AEM) to permafrost mapping. Such an approach is attractive, particularly in Arctic and Subarctic studies, where ground access is difficult and ecosystems are fragile. In June 2010, the U.S. Geological Survey (USGS) conducted an AEM survey near Fort Yukon, Alaska. The primary focus of this survey was to map the distribution of permafrost in selected areas in order to supply information for the development of groundwater models of the Yukon River Basin. However, the methodologies have more far-reaching ecological and engineering applications. Approximately 1,800 line kilometers were acquired in a combination of typical block style surveying in the immediate area of Fort Yukon and in long reconnaissance lines over a broader area. The widely spaced lines were flown to cross the modern Yukon River in "X" like patterns with intersections at features that have been previously studied (fig. 2). AEM is used to gather data on the electrical resistivity of materials in the subsurface below the flight path of the helicopter, which are then analyzed to interpret the subsurface lithology and the location and extent of permafrost. For this survey, the electrical resistivity was imaged to depths on the order of 50-100 meters. Images from the survey can be qualitatively compared with known permafrost features and suggest new permafrost features. Electrical properties of earth materials are affected by lithology as well as temperature and the presence of ice; frozen materials become substantially more resistive. This allows for the identification of permafrost from the resistivity image (Abraham and others, 2011). In the area of Fort Yukon, the AEM survey shows elevated resistivities extending to depth, likely indicative of thick permafrost. This depth corresponds well to observations from a borehole drilled in the area in the late 1990s, which detected permafrost to a depth of about 100 meters (Clark and others, 2009). In contrast to the area of Fort Yukon, the Yukon River and its floodplain are not associated with deep resistive sediments, suggesting a lack of deep permafrost, at least within the depth range of the AEM mapping (fig. 3).

Yukon River Basin↗

USGS1970

Paleozoic and Precambrian rocks of Alaska and their role in its structural evolution

Acknowledging that there are large gaps in the knowledge of the geology of Alaska, the following threefold subdivision of Alaska into Paleozoic tectonic elements is proposed: Southern Alaska--the Alaska Range and farther south--is the northern end of the Paleozoic Cordilleran geosyncline that rims the eastern Pacific. Northern Alaska--the northeastern Brooks Range and the Arctic Coastal Plain--is underlain by a pre-Upper Devonian fold belt that may continue around the rim of the Canada Basin into the Franklinian geosyncline of the Canadian Arctic Islands. East-central Alaska, with a thinner, mainly carbonate rock section, seems to be a western extension of the Yukon shelf that separates the circum-Arctic geosynclinal trend from the Cordilleran geosyncline along the Pacific margin of southern Alaska.

Alaska↗

USGS1989

Draft generalized geologic map of the Chandler Lake Quadrangle, north-central Alaska

Release of this map in open-file is in response to recent requests for geological information in the central Brooks Range and adjacent Arctic foothills. Upcoming State of Alaska oil and gas lease sales, the White Hills Sale Area 61 (January, 1992), the North Slope Foothills Sale Area 57 (September, 1993), and the Nanushuk Sale Area 77 (May, 1993) are stimulating interest in the geology of the central Arctic foothills. Geological field programs in preparation for lease sales are beginning this summer. Western Geophysical Company has made 800 line miles of reflection seismic data available for the upcoming lease sales, 400 line miles shot during the winter of 1986-87 and 400 line miles shot during the winter of 1988-89. The recently completed geophysical and ongoing geological surveys have prompted requests for timely release of geological information on the central Arctic foothills.

Alaska↗

USGS2019

Geology and assessment of undiscovered oil and gas resources of the Eurasia Basin Province, 2008

The Eurasia Basin Petroleum Province comprises the younger, eastern half of the Arctic Ocean, including the Eurasia Basin and the outboard part of the continental margin of northern Europe in the Barents and Kara Seas. The province includes the slope and rise sedimentary prism of the Lena Delta, the north-facing outer shelf, slope, and rise of the European passive margin, and sedimentary accumulations in the deep Nansen and Amundsen Basins. The entire province lies north of the Arctic Circle beneath the polar ice cap and includes the North Pole. The province is divided into four assessment units (AUs). The Lena Prodelta AU in the eastern part of the province consists of the deep-marine part of the Lena Delta, which has been deposited across the Gakkel Ridge, an ultraslow spreading ridge. The Nansen Basin Margin AU in the southern part of the province comprises the Cenozoic passive margin sequence of the rift margin of the western (European) part of the Eurasian plate. This AU spans the continent-ocean boundary and includes prerift strata along the outer continental margin. The Nansen Basin and Amundsen Basin AUs encompass the deep abyssal plains of the Eurasia Basin. Lying south of the Gakkel Ridge spreading center, the sedimentary fill of Nansen Basin AU consists of the distal clinoform deposits shed from the western Eurasia passive margin. North of the Gakkel Ridge, Amundsen Basin AU consists of a nascent distal passive-margin sequence derived from the adjacent Lomonosov Ridge and overlying flat-lying deep marine strata shed from distant source areas in Siberia and Greenland after the Lomonosov Ridge subsided below sea level at about 50 Ma. The primary petroleum system thought to be present is sourced in ~50–44 Ma (early to middle Eocene) condensed pelagic deposits that could be widespread in the province. Mean estimates of undiscovered, technically recoverable petroleum resources include <1 billion barrels of oil (BBO) and about 1.4 trillion cubic feet (TCF) of nonassociated gas in Lena Prodelta AU, and < 0.4 BBO and 3.4 TCF nonassociated gas in the Nansen Basin Margin AU. Quantities of natural gas liquids and associated natural gas also are assessed in each of these AUs. The Nansen Basin and Amundsen Basin AUs were not quantitatively assessed because they were judged to have less than 10 percent probability of containing at least one accumulation of 50 MMBOE (million barrels of oil equivalent), the minimum probability required for evaluation in the U.S. Geological Survey Circum-Arctic Resource Appraisal.

Professional Paper↗

USGS2018

Geology and assessment of undiscovered oil and gas resources of the Mezen’ Basin Province, 2008

The Mezen’ Basin Province is situated along the White and Barents Seas in the northeastern part of the Russian Federation. Only a small area of the province, part of one graben, extends slightly north of the Arctic Circle onto the Kanin-Kola monocline, where it converges with the Timan-Varanger deformed belt and the Fennoscandian shield. The main petroleum potential in the Mezen’ Basin Province is associated with grabens in which clastic Proterozoic source and reservoir rocks are present. One Proterozoic-Paleozoic Composite Total Petroleum System was defined, although Paleozoic and younger strata are too thin (<1–2 km) for significant petroleum accumulation. The total thickness of the sedimentary interval is <6 km. The Northwest Mezen’ Basin Assessment Unit was delineated north of the Arctic Circle. Proterozoic (Riphean) mudstone is organic rich and thermally mature, providing a source for petroleum; younger Proterozoic (Vendian) rocks are also organic rich but thermally immature (Kuz’min, 2005). Because of its limited extent, the potential for an oil or gas field exceeding the minimum size of 50 million barrels of oil equivalent (MMBOE) within the small graben north of the Arctic Circle is remote (assessment-unit probability, 0.005). Therefore, the Mezen’ Basin Province was not quantitatively assessed.

Mezen’ Basin Province↗

USGS2017

Geology and assessment of undiscovered oil and gas resources of the Northwest Laptev Sea Shelf Province, 2008

The U.S. Geological Survey (USGS) has recently assessed the potential for undiscovered oil and gas resources in the Northwest Laptev Sea Shelf Province as part of the USGS Circum-Arctic Resource Appraisal. The province is in the Russian Arctic, east of Severnaya Zemlya and the Taimyr fold-and-thrust belt. The province is separated from the rest of the Laptev Sea Shelf by the Severnyi transform fault. One assessment unit (AU) was defined for this study: the Northwest Laptev Sea Shelf AU. The estimated mean volumes of undiscovered petroleum resources in the Northwest Laptev Sea Shelf Province are approximately 172 million barrels of crude oil, 4.5 trillion cubic feet of natural gas, and 119 million barrels of natural-gas liquids, north of the Arctic Circle.

Professional Paper↗

USGS2018

Geology and assessment of undiscovered oil and gas resources of the Lena-Anabar Basin Province, 2008

The U.S. Geological Survey (USGS) assessed the potential for undiscovered oil and gas resources of the Lena-Anabar Basin Province as part of its Circum-Arctic Resource Appraisal program. The province is in the Russian High Arctic and is located between the Laptev Sea and the Siberian craton. Three assessment units (AUs) were defined for this study—the Lena-Anabar Basin AU, the Lena-Anabar Basin Updip AU, and the Sukhan-Motorchun Riphean Rift AU—and were assessed for undiscovered, technically recoverable resources. The estimated mean volumes of undiscovered oil and gas resources for the Lena-Anabar Basin Province are ~2 billion barrels of crude oil, ~2 trillion cubic feet of natural gas, and <1 billion barrels of natural gas liquids. All of the undiscovered petroleum resources are north of the Arctic Circle.

Lena-Anabar Basin Province↗

USGS2017

Geology and assessment of undiscovered oil and gas resources of the Lena-Vilyui Basin Province, 2008

The U.S. Geological Survey (USGS) recently assessed the potential for undiscovered oil and gas resources of the Lena-Vilyui Basin Province, north of the Arctic Circle, as part of the Circum-Arctic Resource Appraisal program. The province is in the Russian Federation and is situated between the Verkhoyansk fold-and-thrust belt and the Siberian craton. The one assessment unit (AU) defined for this study—the Northern Priverkhoyansk Foredeep AU—was assessed for undiscovered, technically recoverable resources. The estimated mean volumes of undiscovered resources for the Northern Priverkhoyansk Foredeep in the Lena-Vilyui Basin Province are ~400 million barrels of crude oil, 1.3 trillion cubic feet of natural gas, and 40 million barrels of natural-gas liquids, practically all (99.49 percent) of which is north of the Arctic Circle.

Lena-Vilyui Basin Province↗

USGS2020

Geometric and material variability influences stress states relevant to coastal permafrost bluff failure

Scientific knowledge and engineering tools for predicting coastal erosion are largely confined to temperate climate zones that are dominated by non-cohesive sediments. The pattern of erosion exhibited by the ice-bonded permafrost bluffs in Arctic Alaska, however, is not well explained by these tools. Investigation of the oceanographic, thermal, and mechanical processes that are relevant to permafrost bluff failure along Arctic coastlines is needed. We conducted physics-based numerical simulations of mechanical response that focus on the impact of geometric and material variability on permafrost bluff stress states for a coastal setting in Arctic Alaska that is prone to toppling mode block failure. Our three-dimensional geomechanical boundary-value problems output static realizations of compressive and tensile stresses. We use these results to quantify variability in the loci of potential instability. We observe that niche dimension affects the location and magnitude of the simulated maximum tensile stress more strongly than the bluff height, ice wedge polygon size, ice wedge geometry, bulk density, Young’s Modulus, and Poisson’s Ratio. Our simulations indicate that variations in niche dimension can produce radically different potential failure areas and that even relatively shallow vertical cracks can concentrate displacement within ice-bonded permafrost bluffs. These findings suggest that stability assessment approaches, for which the geometry of the failure plane is delineated a priori, may not be ideal for coastlines similar to our study area and could hamper predictions of erosion rates and nearshore sediment/biogeochemical loading.

Frontiers in Earth Science↗

USGS2012

Canada Basin revealed

More than 15,000 line-km of new regional seismic reflection and refraction data in the western Arctic Ocean provide insights into the tectonic and sedimentologic history of Canada Basin, permitting development of new geologic understanding in one of Earth's last frontiers. These new data support a rotational opening model for southern Canada Basin. There is a central basement ridge possibly representing an extinct spreading center with oceanic crustal velocities and blocky basement morphology characteristic of spreading centre crust surrounding this ridge. Basement elevation is lower in the south, mostly due to sediment loading subsidence. The sedimentary succession is thickest in the southern Beaufort Sea region, reaching more than 15 km, and generally thins to the north and west. In the north, grabens and half-grabens are indicative of extension. Alpha-Mendeleev Ridge is a large igneous province in northern Amerasia Basin, presumably emplaced synchronously with basin formation. It overprints most of northern Canada Basin structure. The seafloor and sedimentary succession of Canada Basin is remarkably flat-lying in its central region, with little bathymetric change over most of its extent. Reflections that correlate over 100s of kms comprise most of the succession and on-lap bathymetric and basement highs. They are interpreted as representing deposits from unconfined turbidity current flows. Sediment distribution patterns reflect changing source directions during the basin’s history. Initially, probably late Cretaceous to Paleocene synrift sediments sourced from the Alaska and Mackenzie-Beaufort margins. This unit shows a progressive series of onlap unconformities with a younging trend towards Alpha and Northwind ridges, likely a response to contemporaneous subsidence. Sediment source direction appeared to shift to the Canadian Arctic Archipelago margin for the Eocene and Oligocene, likely due to uplift of Arctic islands during the Eurekan Orogeny. The final stage of sedimentation appears to be from the Mackenzie-Beaufort region for the Miocene and Pliocene when drainage patterns shifted in the Yukon and Alaska to the Mackenzie valley. Upturned reflections at onlap positions may indicate syn-depositional subsidence. There is little evidence, at least at a regional seismic data scale, of contemporaneous or post-depositional sediment reworking, suggesting little large-scale geostrophic or thermohaline-driven bottom current activity.

Conference Paper↗

USGS2016

Changing times, changing stories: Generational differences in climate change perspectives from four remote indigenous communities in Subarctic Alaska

Indigenous Arctic and Subarctic communities currently are facing a myriad of social and environmental changes. In response to these changes, studies concerning indigenous knowledge (IK) and climate change vulnerability, resiliency, and adaptation have increased dramatically in recent years. Risks to lives and livelihoods are often the focus of adaptation research; however, the cultural dimensions of climate change are equally important because cultural dimensions inform perceptions of risk. Furthermore, many Arctic and Subarctic IK climate change studies document observations of change and knowledge of the elders and older generations in a community, but few include the perspectives of the younger population. These observations by elders and older generations form a historical baseline record of weather and climate observations in these regions. However, many indigenous Arctic and Subarctic communities are composed of primarily younger residents. We focused on the differences in the cultural dimensions of climate change found between young adults and elders. We outlined the findings from interviews conducted in four indigenous communities in Subarctic Alaska. The findings revealed that (1) intergenerational observations of change were common among interview participants in all four communities, (2) older generations observed more overall change than younger generations interviewed by us, and (3) how change was perceived varied between generations. We defined “observations” as the specific examples of environmental and weather change that were described, whereas “perceptions” referred to the manner in which these observations of change were understood and contextualized by the interview participants. Understanding the differences in generational observations and perceptions of change are key issues in the development of climate change adaptation strategies.

Alaska↗

USGS2003

Gyrfalcon diet in central west Greenland during the nestling period

We studied food habits of Gyrfalcons (Falco rusticolus) nesting in central west Greenland in 2000 and 2001 using three sources of data: time-lapse video (3 nests), prey remains (22 nests), and regurgitated pellets (19 nests). These sources provided different information describing the diet during the nesting period. Gyrfalcons relied heavily on Rock Ptarmigan (Lagopus mutus) and arctic hares (Lepus arcticus). Combined, these species contributed 79-91% of the total diet, depending on the data used. Passerines were the third most important group. Prey less common in the diet included waterfowl, arctic fox pups (Alopex lagopus), shorebirds, gulls, alcids, and falcons. All Rock Ptarmigan were adults, and all but one arctic hare were young of the year. Most passerines were fledglings. We observed two diet shifts, first from a preponderance of ptarmigan to hares in mid-June, and second to passerines in late June. The video-monitored Gyrfalcons consumed 94-110 kg of food per nest during the nestling period, higher than previously estimated. Using a combination of video, prey remains, and pellets was important to accurately document Gyrfalcon diet, and we strongly recommend using time-lapse video in future diet studies to identify biases in prey remains and pellet data.

The Condor↗

USGS2003

Gyrfalcon diet in central west Greenland during the nesting period

Condor↗

USGS2010

The PRISM3D paleoenvironmental reconstruction

The Pliocene Research, Interpretation and Synoptic Mapping (PRISM) paleoenvironmental reconstruction is an internally consistent and comprehensive global synthesis of a past interval of relatively warm and stable climate. It is regularly used in model studies that aim to better understand Pliocene climate, to improve model performance in future climate scenarios, and to distinguish model-dependent climate effects. The PRISM reconstruction is constantly evolving in order to incorporate additional geographic sites and environmental parameters, and is continuously refined by independent research findings. The new PRISM three dimensional (3D) reconstruction differs from previous PRISM reconstructions in that it includes a subsurface ocean temperature reconstruction, integrates geochemical sea surface temperature proxies to supplement the faunal-based temperature estimates, and uses numerical models for the first time to augment fossil data. Here we describe the components of PRISM3D and describe new findings specific to the new reconstruction. Highlights of the new PRISM3D reconstruction include removal of Hudson Bay and the Great Lakes and creation of open waterways in locations where the current bedrock elevation is less than 25m above modern sea level, due to the removal of the West Antarctic Ice Sheet and the reduction of the East Antarctic Ice Sheet. The mid-Piacenzian oceans were characterized by a reduced east-west temperature gradient in the equatorial Pacific, but PRISM3D data do not imply permanent El Niño conditions. The reduced equator-to-pole temperature gradient that characterized previous PRISM reconstructions is supported by significant displacement of vegetation belts toward the poles, is extended into the Arctic Ocean, and is confirmed by multiple proxies in PRISM3D. Arctic warmth coupled with increased dryness suggests the formation of warm and salty paleo North Atlantic Deep Water (NADW) and a more vigorous thermohaline circulation system that may have provided the enhanced ocean heat transport necessary to move warm surface water to the Arctic. New deep ocean temperature data also suggests greater warmth and further southward penetration of paleo NADW.

Stratigraphy↗