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Saito K.,University of Alaska Fairbanks | Saito K.,Japan Agency for Marine - Earth Science and Technology | Zhang T.,Lanzhou University | Zhang T.,University of Colorado at Boulder | And 6 more authors.
Ecological Applications | Year: 2013

This synthesis paper provides a summary of the major components of the physical terrestrial Arctic and the influences of their changes upon the larger eco-climate system. Foci here are snow cover, permafrost, and land hydrology. During the last century, snow cover duration has shortened in a large portion of the circum-Arctic, mainly because of its early northward retreat in spring due to warming. Winter precipitation has generally increased, resulting in an increase in maximum snow depth over large areas. This is consistent with the increase in river discharge over large Russian watersheds. Soil temperature has also increased, and the active layer has deepened in most of the permafrost regions, whereas thinning of the seasonally frozen layer has been observed in areas not underlain by permafrost. These active components are mutually interrelated, conditioned by ambient micro- to landscape-level topography and local surface and subsurface conditions, and they are closely related with vegetation and ecology, as evidenced by evolution in the late Quaternary. Further, we provide examples and arguments for discussions on the pathways through which changes in the Arctic terrestrial system can affect or propagate to remote areas beyond the Arctic, reaching to the extratropics in the larger climate system. These considerations include dynamical and thermodynamical responses and feedbacks, modification of hemisphere-scale atmospheric circulation associated with troposphere-stratosphere couplings, and moisture intrusion at a continental scale.© 2013 by the Ecological Society of America.

Romanovsky V.E.,University of Alaska Fairbanks | Drozdov D.S.,Earth Cryosphere Institute | Oberman N.G.,MIRECO Mining Company | Malkova G.V.,Earth Cryosphere Institute | And 8 more authors.
Permafrost and Periglacial Processes | Year: 2010

The results of the International Permafrost Association's International Polar Year Thermal State of Permafrost (TSP) project are presented based on field measurements from Russia during the IPY years (2007-09) and collected historical data. Most ground temperatures measured in existing and new boreholes show a substantial warming during the last 20 to 30 years. The magnitude of the warming varied with location, but was typically from 0.5°C to 2°C at the depth of zero annual amplitude. Thawing of Little Ice Age permafrost is ongoing at many locations. There are some indications that the late Holocene permafrost has begun to thaw at some undisturbed locations in northeastern Europe and northwest Siberia. Thawing of permafrost is most noticeable within the discontinuous permafrost domain. However, permafrost in Russia is also starting to thaw at some limited locations in the continuous permafrost zone. As a result, a northward displacement of the boundary between continuous and discontinuous permafrost zones was observed. This data set will serve as a baseline against which to measure changes of near-surface permafrost temperatures and permafrost boundaries, to validate climate model scenarios, and for temperature reanalysis. © 2010 John Wiley & Sons, Ltd.

Liljedahl A.K.,University of Alaska Fairbanks | Boike J.,Alfred Wegener Institute for Polar and Marine Research | Daanen R.P.,354 College Road | Fedorov A.N.,Melnikov Permafrost Institute | And 17 more authors.
Nature Geoscience | Year: 2016

Ice wedges are common features of the subsurface in permafrost regions. They develop by repeated frost cracking and ice vein growth over hundreds to thousands of years. Ice-wedge formation causes the archetypal polygonal patterns seen in tundra across the Arctic landscape. Here we use field and remote sensing observations to document polygon succession due to ice-wedge degradation and trough development in ten Arctic localities over sub-decadal timescales. Initial thaw drains polygon centres and forms disconnected troughs that hold isolated ponds. Continued ice-wedge melting leads to increased trough connectivity and an overall draining of the landscape. We find that melting at the tops of ice wedges over recent decades and subsequent decimetre-scale ground subsidence is a widespread Arctic phenomenon. Although permafrost temperatures have been increasing gradually, we find that ice-wedge degradation is occurring on sub-decadal timescales. Our hydrological model simulations show that advanced ice-wedge degradation can significantly alter the water balance of lowland tundra by reducing inundation and increasing runoff, in particular due to changes in snow distribution as troughs form. We predict that ice-wedge degradation and the hydrological changes associated with the resulting differential ground subsidence will expand and amplify in rapidly warming permafrost regions. © 2016 Macmillan Publishers Limited. All rights reserved.

Schaefer K.,University of Colorado at Boulder | Lantuit H.,Alfred Wegener Institute for Polar and Marine Research | Lantuit H.,University of Potsdam | Romanovsky V.E.,University of Alaska Fairbanks | And 3 more authors.
Environmental Research Letters | Year: 2014

Degrading permafrost can alter ecosystems, damage infrastructure, and release enough carbon dioxide (CO2) and methane (CH4) to influence global climate. The permafrost carbon feedback (PCF) is the amplification of surface warming due to CO2 and CH4 emissions from thawing permafrost. An analysis of available estimates PCF strength and timing indicate 120α85 Gt of carbon emissions from thawing permafrost by 2100. This is equivalent to 5.7α4.0% of total anthropogenic emissions for the Intergovernmental Panel on Climate Change (IPCC) representative concentration pathway (RCP) 8.5 scenario and would increase global temperatures by 0.29α0.21 °C or 7.8α5.7%. For RCP4.5, the scenario closest to the 2 °C warming target for the climate change treaty, the range of cumulative emissions in 2100 from thawing permafrost decreases to between 27 and 100 Gt C with temperature increases between 0.05 and 0.15 °C, but the relative fraction of permafrost to total emissions increases to between 3% and 11%. Any substantial warming results in a committed, long-term carbon release from thawing permafrost with 60% of emissions occurring after 2100, indicating that not accounting for permafrost emissions risks overshooting the 2 °C warming target. Climate projections in the IPCC Fifth Assessment Report (AR5), and any emissions targets based on those projections, do not adequately account for emissions from thawing permafrost and the effects of the PCF on global climate. We recommend the IPCC commission a special assessment focusing on the PCF and its impact on global climate to supplement the AR5 in support of treaty negotiation. © 2014 IOP Publishing Ltd.

Jafarov E.E.,University of Colorado at Boulder | Jafarov E.E.,University of Alaska Fairbanks | Romanovsky V.E.,University of Alaska Fairbanks | Romanovsky V.E.,Earth Cryosphere Institute | And 3 more authors.
Environmental Research Letters | Year: 2013

Fire is an important factor controlling the composition and thickness of the organic layer in the black spruce forest ecosystems of interior Alaska. Fire that burns the organic layer can trigger dramatic changes in the underlying permafrost, leading to accelerated ground thawing within a relatively short time. In this study, we addressed the following questions. (1) Which factors determine post-fire ground temperature dynamics in lowland and upland black spruce forests? (2) What levels of burn severity will cause irreversible permafrost degradation in these ecosystems? We evaluated these questions in a transient modeling-sensitivity analysis framework to assess the sensitivity of permafrost to climate, burn severity, soil organic layer thickness, and soil moisture content in lowland (with thick organic layers, ∼80 cm) and upland (with thin organic layers, ∼30 cm) black spruce ecosystems. The results indicate that climate warming accompanied by fire disturbance could significantly accelerate permafrost degradation. In upland black spruce forest, permafrost could completely degrade in an 18 m soil column within 120 years of a severe fire in an unchanging climate. In contrast, in a lowland black spruce forest, permafrost is more resilient to disturbance and can persist under a combination of moderate burn severity and climate warming. © 2013 IOP Publishing Ltd.

Saito K.,University of Alaska Fairbanks | Saito K.,Japan Agency for Marine - Earth Science and Technology | Sueyoshi T.,Japan Agency for Marine - Earth Science and Technology | Marchenko S.,University of Alaska Fairbanks | And 7 more authors.
Climate of the Past | Year: 2013

Here, global-scale frozen ground distribution from the Last Glacial Maximum (LGM) has been reconstructed using multi-model ensembles of global climate models, and then compared with evidence-based knowledge and earlier numerical results. Modeled soil temperatures, taken from Paleoclimate Modelling Intercomparison Project phase III (PMIP3) simulations, were used to diagnose the subsurface thermal regime and determine underlying frozen ground types for the present day (pre-industrial; 0 kya) and the LGM (21 kya). This direct method was then compared to an earlier indirect method, which categorizes underlying frozen ground type from surface air temperature, applying to both the PMIP2 (phase II) and PMIP3 products. Both direct and indirect diagnoses for 0 kya showed strong agreement with the present-day observation-based map. The soil temperature ensemble showed a higher diversity around the border between permafrost and seasonally frozen ground among the models, partly due to varying subsurface processes, implementation, and settings. The area of continuous permafrost estimated by the PMIP3 multi-model analysis through the direct (indirect) method was 26.0 (17.7) million km2 for LGM, in contrast to 15.1 (11.2) million km2 for the pre-industrial control, whereas seasonally frozen ground decreased from 34.5 (26.6) million km2 to 18.1 (16.0) million km2. These changes in area resulted mainly from a cooler climate at LGM, but from other factors as well, such as the presence of huge land ice sheets and the consequent expansion of total land area due to sea-level change. LGM permafrost boundaries modeled by the PMIP3 ensemble - improved over those of the PMIP2 due to higher spatial resolutions and improved climatology - also compared better to previous knowledge derived from geomorphological and geocryological evidence. Combinatorial applications of coupled climate models and detailed stand-alone physical-ecological models for the cold-region terrestrial, paleo-, and modern climates will advance our understanding of the functionality and variability of the frozen ground subsystem in the global eco-climate system. © Author(s) 2013. CC Attribution 3.0 License.

Saito K.,Japan Agency for Marine - Earth Science and Technology | Saito K.,University of Alaska Fairbanks | Marchenko S.,University of Alaska Fairbanks | Romanovsky V.,University of Alaska Fairbanks | And 5 more authors.
Boreas | Year: 2014

A high-resolution map of potential frozen ground distribution in NE Asia (90-150°E, 25-60°N) at the period of the Last Permafrost Maximum (LPM, c. 21000 years ago) was dually reconstructed by means of a statistical classification using air freezing and thawing indices and a topographical downscaling using a digital relief model (ETOPO1). Background LPM climate data were derived from global climate model simulations of the Paleoclimate Model Intercomparison Project, Phase II (PMIP2). The reconstructed LPM map shows the southward shift of the southern limit of climate-driven permafrost by 400-1500km, with the greatest advance in the western sector (90-110°E), encompassing an area from central Siberia to most of the Altai area. The advance of environmentally conditional permafrost and seasonally frozen ground was greatest in the eastern sector (110-150°E), with an average shift of about 450km. The descent of the lower limit of LPM alpine permafrost was in the range of 400-800m. A comparison of the reconstructed map with published literature shows that this method, simplistically constructed yet effectively recognizing seasonality, continentality and topography, captures local features better than more elaborate methods. The sensitivity examination of a constant atmospheric lapse rate shows that altitudes of 2000-5000ma.s.l. were most sensitive, though with only a limited effect on overall LPM distribution. © 2013 The Boreas Collegium.

Jafarov E.E.,University of Alaska Fairbanks | Marchenko S.S.,University of Alaska Fairbanks | Romanovsky V.E.,University of Alaska Fairbanks | Romanovsky V.E.,Earth Cryosphere Institute
Cryosphere | Year: 2012

Climate projections for the 21st century indicate that there could be a pronounced warming and permafrost degradation in the Arctic and sub-Arctic regions. Climate warming is likely to cause permafrost thawing with subsequent effects on surface albedo, hydrology, soil organic matter storage and greenhouse gas emissions.

To assess possible changes in the permafrost thermal state and active layer thickness, we implemented the GIPL2-MPI transient numerical model for the entire Alaska permafrost domain. The model input parameters are spatial datasets of mean monthly air temperature and precipitation, prescribed thermal properties of the multilayered soil column, and water content that are specific for each soil class and geographical location. As a climate forcing, we used the composite of five IPCC Global Circulation Models that has been downscaled to 2 by 2 km spatial resolution by Scenarios Network for Alaska Planning (SNAP) group.

In this paper, we present the modeling results based on input of a five-model composite with A1B carbon emission scenario. The model has been calibrated according to the annual borehole temperature measurements for the State of Alaska. We also performed more detailed calibration for fifteen shallow borehole stations where high quality data are available on daily basis. To validate the model performance, we compared simulated active layer thicknesses with observed data from Circumpolar Active Layer Monitoring (CALM) stations. The calibrated model was used to address possible ground temperature changes for the 21st century. The model simulation results show widespread permafrost degradation in Alaska could begin between 2040-2099 within the vast area southward from the Brooks Range, except for the high altitude regions of the Alaska Range and Wrangell Mountains. © Author(s) 2012. CC Attribution 3.0 License.

Rinke A.,Alfred Wegener Institute for Polar and Marine Research | Matthes H.,Alfred Wegener Institute for Polar and Marine Research | Christensen J.H.,Danish Meteorological Institute | Christensen J.H.,Greenland Institute of Natural Resources | And 4 more authors.
Global and Planetary Change | Year: 2012

A regional climate model with high horizontal resolution (25. km) is used to downscale 20-year-long time slices of present-day (1980-1999) and future (2046-2065, 2080-2099) Arctic climate, as simulated by the ECHAM5/MPI-OM general circulation model under the A1B emission scenario. Changes in simulated air temperature and derived indices at the end of the century indicate that significant impacts on permafrost conditions should be expected. But the magnitude of the change is regionally conditioned beyond what is obvious: Warm permafrost in the sporadic to discontinuous zone is threatened and may degrade or even complete thaw before the end of the century. A decrease in freezing and increase in thawing degree-days is interpreted as potential decrease in seasonal freeze depth and increase in active layer thickness (ALT). We show that for some regions increasing maximum summer temperature is associated with an increase of interannual temperature variability in summer, while in other regions decreased maximum summer temperatures are related to decreased variability. The occurrence of warm/cold summers and spells changes significantly in the future time slices using the present-day criteria for classification. Taken together this implies a regionally varying exposure to significant change in permafrost conditions. In addition to these aspects of the general warming trend that would promote an increase in ALT and a northward shift of the southern permafrost boundary, an analysis of the occurrence of warm summers and spells highlight some particularly vulnerable regions for permafrost degradation (e.g. West Siberian Plain, Laptev Sea coast, Canadian Archipelago), but also some less vulnerable regions (e.g. Mackenzie Mountains). © 2011 Elsevier B.V.

Nicolsky D.J.,University of Alaska Fairbanks | Romanovsky V.E.,University of Alaska Fairbanks | Romanovsky V.E.,Earth Cryosphere Institute | Romanovskii N.N.,Moscow State University | And 3 more authors.
Journal of Geophysical Research: Earth Surface | Year: 2012

Models of sub-sea permafrost evolution vary significantly in employed physical assumptions regarding the paleo-geographic scenario, geological structure, thermal properties, initial temperature distribution, and geothermal heat flux. This work aims to review the underlying assumptions of these models as well as to incorporate recent findings, and hence develop an up-to-date model of the sub-sea permafrost dynamics at the Laptev Sea shelf. In particular, the sub-sea permafrost model developed here incorporates thermokarst and land-ocean interaction theory, and shows that the sediment salinity and a temperature-based parametrization of the unfrozen water content are critical factors influencing sub-sea permafrost dynamics. From the numerical calculations, we suggest development of open taliks may occur beneath submerged thaw lakes within a large area of the shelf. © 2012. American Geophysical Union. All Rights Reserved.

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