A42A-01 INVITED 10:22h
Evidence for Arctic Climate Change
Climate variability and change has become important issues in the Arctic over the past few decades. The Arctic Climate Impact Assessment (ACIA), a four-year scientific assessment of climate change of the Arctic, was established and charged to (i) evaluate and synthesize knowledge on the impacts and consequences of climate variability and change and increased ultraviolet radiation across the Arctic region, and (ii) support decision and policy making processes for the eight Arctic countries and their residents. This paper will provide an overview of the key findings from the scientific aspects of the Assessment. Past and present results are based on published data and information while the projections are based on five of the IPCC models driven by the B2, and in some cases A2, IPCC scenarios. Examples of the key findings are: Arctic climate is changing rapidly: Average Arctic temperature has risen by about 1°C in the past 100 years, nearly twice the global average, with the steepest increase in the last three decades. Accelerating climate changes are projected: The Arctic is very likely to warm an additional 3-9°C over the next 100 years, about twice the projected global average. Further, precipitation is likely to increase by about 8% by mid-century and 20% by the end of the century. Regional variations are observed and projected: Some parts of the Arctic have warmed more than others (e.g., some parts of Alaska have warmed at 5-10 times the global average over the past 30 years) while some have even cooled slightly. Arctic processes amplify global change: Melting of reflective Arctic snow and ice increases heat absorption of the exposed land and ocean, further warming the planet. Increases in glacial melt, precipitation and river runoff bring more freshwater to the ocean, raising sea level globally. Warming of Arctic soils and coastal oceans is likely to lead to increased release of carbon dioxide and methane. Reduced sea ice will enhance shipping opportunities: Sea ice retreat is very likely to seasonally open the Northeast and Northwest passages, making trans-Arctic shipping during summer possible within a few decades. Permafrost thawing will impact infrastructure: Climate change is likely to have significant impacts on existing buildings, roads, pipelines, and industrial facilities. Transportation on land will increasingly be disrupted by the failure of ice roads and tundra to freeze sufficiently to permit travel. Risks to many coastal areas will increase: Coastal erosion will be a growing problem do to substantial reductions in coastal sea ice in the spring and fall, which allows higher storm surges to reach shore which when combined with thawing coastal permafrost adds to the vulnerability of these coastlines. The Assessment has been completed and two peer-reviewed scientific documents (an Overview document and the complete scientific assessment0 will be available from Cambridge University Press by the end of the year (2004).
http://www.acia.uaf.edu
A42A-02 INVITED 10:40h
Regional Climate Variability and Decisionmaking in the Southwest
The NOAA-funded Climate Assessment for the Southwest (CLIMAS) has been working with stakeholder-partners for six years to develop research, hydroclimate information products, and decision support tools that meet the needs of decisionmakers in Arizona and New Mexico. The goal of this user-inspired multidisciplinary research is to help reduce vulnerability to climate variability and change. CLIMAS has primarily examined climate variability and its impacts on the region. In the first phase of the project, CLIMAS researchers determined that interannual and decadal variability were topics more palatable to most decisionmakers than anthropogenic climate change. These topics are less emotionally charged, and easier to relate to stakeholder year-to-year operations and life experience. Our vision has been that by helping stakeholders to understand and prepare for climate variability and reduce their vulnerability to climate variability, we lay the foundation for decisionmakers to consider long-term anthropogenic climate changes their vulnerabilities to such changes. This presentation examines the role of understanding regional decisionmaking contexts in CLIMAS efforts to convey information on climate variability and its impacts to regional stakeholders.
A42A-03 11:00h
Impacts of lake-effect snow on forest communities in the Great Lakes region
Lake-effect snow (LES) increases winter precipitation in the Great Lakes snowbelts by up to 100%. The ecological effects of LES remain poorly documented. We coupled GIS and lake-sediment analyses to examine how spatial and temporal variations in LES interact with glacial landforms to impact forest communities in northern Lower Michigan. GIS analysis reveals that snowfall is the most important among several environmental variables (e.g. landform, summer precipitation) influencing the spatial distribution of upland forest types. Mesic forests dominate on all landforms (e.g. outwash, till) in areas receiving LES, but they are restricted to fine-textured (primarily till) soils in nearby areas outside the snowbelt. Oxygen isotopes and pollen preserved in lake sediments suggest that temporal changes in upland vegetation relate to the snowbelt establishment during the Holocene. We compared paleorecords from two lakes inside the snowbelt (Huffman Lake, HL, and Clifford Lake, CL) and two lakes outside the snowbelt (O'Brien Lake, OB, and Horseshoe Lake, HS). HL and OB are situated in outwash whereas CL and HS are situated in till. Thus the four lakes are juxtaposed such that the effects of LES versus glacial landform can be evaluated. At HL, a stepwise decline in \delta$^{18}$O of 2\permil occurs between 6500 calibrated years before present (BP) and 4000 BP followed by a slight decline (0.2\permil) in the past 4000 years. The major \delta$^{18}$O decline probably reflects the establishment of snowbelts because LES is depleted in $^{18}$O. Outside the snowbelt at OB, \delta$^{18}$O declines gradually by 1.2\permil between 6500 BP and the present, with no stepwise shift between 6500 BP and 4500 BP. Detrended correspondence analysis of pollen percentages reveals two distinct vegetation types in the past 6500 years: a xeric type dominated by {\it Pinus}, and a mesic type dominated by northern hardwoods (e.g. {\it Fagus, Tsuga}). At HL and CL a clear shift from xeric to mesic vegetation occurred around 5000 BP. A similar shift never occurred at HS or OB. Differences in vegetation between snowbelt and non-snowbelt sites were far greater than those between the two landforms. Pollen percentages of mesic taxa are higher on till (32% at HS) than on outwash (25% at OB), but neither site approaches the 70% mesic taxa attained at HL (snowbelt outwash). The marked difference in the magnitudes of vegetation change between the snowbelt and non-snowbelt sites cannot be attributed to a mid-Holocene climatic shift throughout the region and/or soil-substrate effects. These data suggest that LES is a dominant factor controlling the spatial and temporal patterns of forest communities around the Great Lakes. They also imply that the mesic plant communities in that region may be in jeopardy if snow is diminished by anthropogenic climatic warming.
A42A-04 11:15h
Multiple Indicators of Climate Change Over the Past Century in New England
As part of the Atmospheric Investigation, Regional Modeling, Analysis and Prediction (AIRMAP) project, we have developed a series of indicators of climate change in New England from instrumental and observational records. This includes changes in atmospheric and sea surface temperature, annual precipitation, precipitation from intense events, ice out dates, length of growing season, and days with snow on ground. While there is some spatial variability, these indicators overall show that New England's climate over the past century has become warmer and wetter. The largest seasonal warming has occurred during the winter, and the increase in precipitation is due mainly to an increase in extreme precipitation events (more than two inches of rain over a 48 hour period). The indicators data will be published as a report for the general public and is also available in easy to view formats on the AIRMAP web site (airmap.unh.edu), along with real-time air quality data, so that the New Englander's can investigate climate change in their own backyard.
A42A-05 11:30h
The Role of Teleconnections in Rocky Mountain Springtime Warming
Using data from 296 stations in Colorado, Montana, New Mexico, and Wyoming, mean spring temperatures for the period 1949-2003 were analyzed to document the spatial and temporal component of temperature trends, identify potential differences in climate change at mountain versus steppe locations, and to assess regional response to atmospheric and oceanic teleconnections. Spring temperature and precipitation in this region are very important for water resources, forest fire conditions, and summer drought severity. Accordingly, many studies have focused on the changing nature of spring climate in the Rocky Mountain States. Of the 296 stations analyzed, 222 demonstrated significant trends in mean spring temperature as indicated by a linear regression analysis using a significance level of 0.10; only two stations demonstrated a statistically significant decrease in temperature over the 55-year period. The region wide warming ranged from 2.06°C in Montana to 1.34°C in New Mexico. The north-south gradient also exists in two other measures of temperature change, the number of stations with significant trends and the number of stations in each state with a warming trend in excess of 2°C. Across the region, there is little indication that sites at higher elevation are warming at a faster rate than lowland stations. In fact, there is evidence that grassland locations in eastern Montana are warming much faster than valley or mountain sites in central or western portions of the state. The warming at stations east of 106°W in Montana is 0.61°C degrees higher than the rest of the state, a statistically significant result. The plains and mountain station difference in warming was not found elsewhere in the research. While the entire region has experienced spring warming over the past 55 years, there are different atmospheric and oceanic teleconnection associated with this phenomenon. The Pacific North American (PNA) teleconnection is important regionally, but the importance of both the Pacific Decadal Oscillation (PDO) and North Pacific (NP) are generally limited to Montana. The El-Nino Southern Oscillation (ENSO) is a primary control on winter and spring climate in Montana, Colorado, and New Mexico, but the direction of the relationship changes from north to south. Zero-lag correlations between the various teleconnections and spring temperatures are usually quite high. However, more important for water resources management and agriculture, the persistence of the teleconnections offers some predictive capability in forecasting spring temperatures from late fall or winter indices. For instance, the correlation between the winter ENSO index and spring temperatures in New Mexico and Colorado is actually stronger than that with no lag. Due to the complex role atmospheric and oceanic teleconnections play in modulating springtime climate in the Rocky Mountains, canonical correlation analysis was performed between the station temperature dataset and sea-surface temperature (SST) and upper-level height fields.
A42A-06 11:42h
Trends in Runoff and Soil Moisture in the Western U.S. from 1915-2003
Observational studies of snowpack in the western U.S. over the second half of the twentieth century show systematic changes in snow accumulation and melt processes associated with warming temperatures. Studies of long-term changes in streamflow over the same period have found systematic changes in the seasonality of runoff with less runoff occurring in spring and early summer and more runoff in winter later in the period. In previous work we have used reconstructions using a macroscale hydrologic model implemented at 1/8th degree latitude-longitude spatial resolution to examine trends in spring snowpack in the western U.S. for a longer period of record that includes most of the 20th century. The model reconstructions also permit an explicit sensitivity analysis of the separate roles of trends in temperature and precipitation. Here we extend these modeling studies to examine trends in runoff and soil moisture associated with the observed (and reconstructed) changes in snowpack. The Variable Infiltration Capacity (VIC) hydrologic model was forced by a new temporally and topographically adjusted climatological (precipitation and temperature) driving data set from 1915-2003. The hydrologic simulations corroborate the observed trends in streamflow over the West from 1950-present, and show dramatic changes in the seasonality of runoff over large spatial scales, particularly in sensitive intermediate elevation (transient snow zone) areas in Washington, Oregon, and California. Soil moisture also shows systematic trends in summer associated with changes in snowmelt runoff, with summer soil moisture declining in areas that have experienced significant reductions in snowpack and/or earlier snowmelt. Sensitivity analysis shows that these trends are most clearly associated with the changes in temperature over the observed period rather than changes in precipitation.
A42A-07 11:54h
Climate Change in the Western United States Grape Growing Regions and its Impact on Wine Quality
Understanding climate change and the potential impacts on natural and human-based systems has become increasingly important as changing levels of greenhouse gases and alterations in earth surface characteristics bring about planetary energy, temperature, and hydrologic changes. Observed trends and potential changes in temperatures exert strong influences on virtually every form of agriculture where production viability may be altered due to changes in winter hardening potential, frost occurrence, growing season lengths, and heat accumulation for ripening potential. The importance of understanding climate change impacts on agriculture is never more evident than with viticulture where many years of experience has resulted in the finest wines being made from grapes grown in geographically distinct regions. However, grapevines are generally grown in regions and under conditions that are considered narrow for a specific variety's optimum quality, ultimately putting it at a greater potential risk from climatic variations and change. Therefore, this research examines trends from 1948-2002 in annual and seasonal frost frequencies, the dates of last spring and first fall frost occurrence, the length of the frost-free period, and growing season average temperatures and degree-days for the principal grape growing regions in California, Oregon, and Washington. Results reveal that, on average, most regions have experienced a decline in frost frequency, earlier last spring frosts, later first fall frosts, longer frost-free periods, and warmer growing seasons with greater heat accumulation. The observed changes in growing season climates are also related to higher average grape sugar concentrations, the resulting potential alcohol levels, and vintage ratings. However, an examination of possible future climate change in these same regions indicate an average growing season warming of 2 degC in the next 50 years. The magnitude of the projected changes will potentially bring about geographical shifts in production viability or cause growers and winemakers to consider varietal or management adaptations to maintain current wine styles and quality.