GC21B-01 INVITED
20th century trends in the Russian hydrologic cycle
Russia has the greatest northern land area, coastal shelves, terrestrial carbon stocks, and river outflows of any nation. Its rivers deliver enormous loads of freshwater, dissolved material, and nutrients to the Arctic Ocean. Carbon storage in Siberian peatlands is large, tightly coupled with hydrology, and depends crucially on whether wetter or drier soil conditions prevail. Therefore, it is plausible that shifts in precipitation, surface wetness, or river runoff could alter the carbon balance, oceanography, and ecoystems of the world's largest high-latitude land mass. Natural hydroclimatic variability, however, is notoriously high in Arctic environments. Therefore, correct identification of long-term anthropogenic trends requires statistical analysis of historical records and sampling over broad geographical areas. This talk provides an overview of the various late 20th century hydrologic trends observed in northern Russia. An overall +7 percent increase in river discharge to the Arctic Ocean now appears to have been driven substantially by increased precipitation. A primary mechanism underlying the discharge increase was enhanced groundwater flow, which rose in the late 20th century. To what extent this phenomenon simply reflects the precipitation increase or another process like improved infiltration through seasonally frozen ground is unknown; what is clear is that minimum river "low-flows" are rising across Russia. In contrast, there has been no broadly coherent increase in the magnitude of the annual spring flood, although some shifts towards earlier peak timing are evident. A dendrochronological reconstruction of annual river outflows suggests that the late 20th century discharge increase, while large, is not unprecedented over the past 200 years. Since no shutdowns in oceanic Meridional Overturning Circulation (MOC) occurred during that time, this finding tempers concerns about any such shutdown in the immediate future. Permafrost thaw is causing Siberian lakes to grow and expand in continuous permafrost but to shrink and drain further south in marginal permafrost. Geochemical samples from West Siberia suggest that thawing permafrost will enhance river loads of total dissolved solids (TDS), dissolved organic carbon (DOC), and nutrients (N, P). However, permafrost thaw cannot fully explain the rising river water levels. The interactions of permafrost and seasonally frozen ground with surface and groundwater systems, and their concomitant response to expected climate warming in the region, remain largely unknown. http://lena.sscnet.ucla.edu
GC21B-02
Projected Changes in Water Resources and Demands in Central Asia and Their Implications for Irrigated Agriculture
Projected climate changes in Central Asia are expected to cause substantial changes in the water balance of its river basins (Syrdarja, Amu-Darya, Lake Balkash). Using hydrologic modeling, climate data, and satellite images we model the current and future water situation. Increases in evapotranspiration and the melting of the glaciers that form a major water resource for the region, will affect soil moisture availability and the amount and timing of river discharge. Their impact on a vastly irrigation dependant agriculture will be discussed. http://www.yale.edu/emcwa/
GC21B-03
Changes in the frequency of precipitation types associated with air temperature over northern Eurasia
This study examines the relationships between the frequency of snowfall, rainfall, mixed solid and liquid, and wet days (including all forms of precipitation) and the air temperature at 80 stations over northern Eurasia during 1936-89 to understand potential changes in precipitation frequency and types under a warming climate over high- latitude land areas. The results suggest that both the snowfall and rainfall days increase as air temperature increases during winter, but decreases during spring. While in the fall, the snowfall day decreases but rainfall day increases and overall less precipitation days as air temperature increases. The study also show that snowfall day would suddenly switch to decrease with air temperature when winter air temperature reach a certain threshold.
GC21B-04
Atmosphere aerosol/dust composition over central Asia and western Siberia derived from snow/ice core records and calibrated with NASA remote sensing data
The vast arid and semi-arid regions of central Asia, Mongolia, and Northern China are the world's second largest source of atmospheric mineral dust. In recent years, severe dust storms in Asia have intensified in frequency, duration, and areal coverage. However, limited spatial and temporal extent of aerosol measurements precludes definitive statements to be made regarding relationship between the Asian aerosol generation and climate. It has been well known that glaciers are the natural archives of environmental records related to past climate and aerosol generation. In our research, we utilized central Asian and western Siberia shallow ice-core records recovered from Altai, Tien Shan and Pamir mountain glaciers. Despite the fact that ice-core data may extend climate/aerosol records back in time, their sparse coverage is inadequate to document aerosol spatial distribution. The NASA products from Aura, Terra and Aqua satellite missions address this gap identifying aerosol sources, transport pathways, and area of deposition. The main objective of our research is to evaluate an affect of climate variability on dynamics of Asian aerosol loading to atmosphere and changes in aerosol transport pathways. Dust particle, major and rare earth element analysis from dust aerosols deposited and accumulated in Altai, Tien Shan and Pamir glaciers suggests that loess from Tajikistan, Afghanistan and north-western China are main sources of aerosol loading into the upper troposphere over the central Asia and western Siberia. At the same time, the soluble ionic component of the ice-cores, related to aerosol generated from evaporate deposits, demonstrated both anthropogenic and natural impacts on atmospheric chemistry over these regions. Large perturbations of Ca2+ derived from CaCO3- rich dust transported from Goby Desert to Altai and Tien Shan. Origin and pathway of the ice-core aerosol depositions for the last 10-years were identified through calibrating ice-core records with dust storm land surface records and remote sensing aerosol data at the monthly/seasonal/annual to event/daily scale. For instance, in southwestern Asia, severe drought developed from 1998 to 2002 has intensified the frequency, duration, and spatial coverage of large dust storms originated in Iran, Afghanistan, Tajikistan, Taklimakan and Goby Deserts. The Pamir and Tien Shan ice-core records revealed, that concentration of major and REE elements during summer is about two times greater in period of 1998-2002 than at the following years. Our qualitative analysis based on ice-core records, the MODIS and SeaWiFS images and determined the origin of dust, transport pathways and aerosol spatial distribution over central Asia and western Siberia in summer 2000, 2001 and 2002. The transport pathways were reconstructed on the basis of visibility observations and NCAR MM5-predicted winds with further validation against of satellite data and isotope- geochemical ice-core data analysis. http://www.sci.uidaho.edu/cae
GC21B-05
Investigating Linkages Between the Dynamics of Dust Events and Synoptic and Land Surface Conditions With a Regional Dust Modeling System WRF-DuMo in Central and East Asia Under the NEESPI Initiative
Growing evidence suggests that land-use/land cover changes and increasing amounts of anthropogenic aerosols might be among the key drivers of observed climate change. Under the Northern Eurasian Earth Science Partnership Initiative (NEESPI) we have been developing a regional dust modeling system by incorporating the dust module DuMo into the NCAR Weather Research and Forecasting (WRF) model. A new terrestrial preprocessor that ingests external aeolian datasets has been developed to support physically-based dust emission schemes implemented in WRF-DuMo. This presentation will focus on the interannual variability of dust events in Central and East Asia in terms of their intensity and duration, addressing the relative importance of prevailing synoptic conditions and regional land surface properties in modulating dust outbreaks. Several studies suggested that during the last two decades dust storm frequency has decreased in both Central and East Asia. The changes in large-scale circulation pattern were suggested to be a main factor. We perform simulations of dust storm events, which occurred under different synoptic conditions for selected spring months over past 50 years, to examine whether the regional modeling system WRF-DuMo is capable of reproducing the observed decreasing trend. In addition, we examine the sensitivity of modeled dust fluxes to meteorological and land surface input parameters for dust events of differing intensity. The results will be presented with the focus on establishing a consistent methodology for developing of a dust event climatology in Central and East Asia.
GC21B-06
Eurasian Hydroclimatology: observations, change, attribution, and impacts
In November, 2007 a workshop was hosted by the International Arctic Research Center at the University of Alaska Fairbanks that had goals closely aligned with the NEESPI program. The goals of this workshop were to 1) describe observed changes in the Eurasian hydroclimatological system over the instrumental period from stations, gridded data, reanalyses and remote sensing; 2) apply our knowledge of biases and inhomogeneity in the observational record; 3) attribute changes to specific physical processes in both the regional and global domain; 4) discuss implications of change for water resources and other human systems. Results from the workshop will be discussed in this presentation.
GC21B-07
Northern Eurasia: Evaluating processes and feedbacks in the context of climate change
Northern Eurasia is undergoing significant changes associated with warming climate and with socio-economic changes during the entire 20th century. Climatic changes over this vast landmass interact and affect the rate of global change through atmosphere-terrestrial-cryosphere feedbacks and through strong biogeophysical and biogeochemical couplings. Current and future interactions and feedbacks to the global system of this carbon- rich, cold region component of the Earth system remain to a large extent unknown. Recent analyses of coupled Atmosphere-Ocean General Circulation Models (AOGCMs) suggest that while model representation of precipitation in the Arctic has modestly improved since the IPCC Third Assessment Report (TAR), there are still large uncertainties in model representation of both precipitation and underlying processes that drive the carbon, hydrology and energy cycles of the northern high latitudes. Model representation of snow, snow redistribution, permafrost, effects of lakes and wetlands are marginal, a problem that is compounded by large uncertainties in observations. Many of the global modeling groups are developing Earth system model components that represent processes specific to the high-latitudes, including organic soils, permafrost, wetlands, ice sheet dynamics and/or biogeography; however, there is no robust or rigorous methodology for testing and evaluating model implementation. A multiple model intercomparison that evaluates biogeochemical, hydrological and biophysical processes and feedbacks in the northern high latitudes with a focus in northern Eurasia across modeling scales is under discussion with the Northern Eurasian Earth Science Partnership Initiative (NEESPI) community. Proposed modeling groups include Earth System Model/AOGCMs, Earth System Models of Intermediate Complexity (EMICs), global Dynamic Vegetation Models (DGVMs), Regional Climate and Air Pollution Models (RCM) customized to northern Eurasia domains, and Stand-level individual based models (IBMs). We suggest an implementation strategy for protocols and results of a cross-model evaluation and solicit input for integration with the International Polar Year syntheses.