We assess changes in runoff timing over the last 55 years at 21 gages unaffected by human influences, in the headwaters of the Columbia‐Missouri Rivers. Linear regression models and tests for significance that control for “false discoveries” of many tests, combined with a conceptual runoff response model, were used to examine the detailed structure of spring runoff timing. We conclude that only about one third of the gages exhibit significant trends with time but over half of the gages tested show significant relationships with discharge. Therefore, runoff timing is more significantly correlated with annual discharge than with time. This result differs from previous studies of runoff in the western USA that equate linear time trends to a response to global warming. Our results imply that predicting future snowmelt runoff in the northern Rockies will require linking climate mechanisms controlling precipitation, rather than projecting response to simple linear increases in temperature.
Migrating waterbirds moving between upper and lower latitudinal breeding and wintering grounds rely on a limited network of endorheic lakes and wetlands when crossing arid continental interiors. Recent drying of global endorheic water stores raises concerns over deteriorating migratory pathways, yet few studies have considered these effects at the scale of continental flyways. Here, we investigate the resiliency of waterbird migration networks across western North America by reconstructing long-term patterns (1984-2018) of terminal lake and wetland surface water area in 26 endorheic watersheds. Findings were partitioned regionally by snowmelt- and monsoon-driven hydrologies and combined with climate and human water-use data to determine their importance in predicting surface water trends. Nonlinear patterns of lake and wetland drying were apparent along latitudinal flyway gradients. Pervasive surface water declines were prevalent in northern snowmelt watersheds (lakes -27%, wetlands -47%) while largely stable in monsoonal watersheds to the south (lakes -13%, wetlands +8%). Monsoonal watersheds represented a smaller proportion of total lake and wetland area, but their distribution and frequency of change within highly arid regions of the continental flyway increased their value to migratory waterbirds. Irrigated agriculture and increasing evaporative demands were the most important drivers of surface water declines. Underlying agricultural and wetland relationships however were more complex. Approximately 7% of irrigated lands linked to flood irrigation and water storage practices supported 61% of all wetland inundation in snowmelt watersheds. In monsoonal watersheds, small earthen dams, meant to capture surface runoff for livestock watering, were a major component of wetland resources (67%) that supported networks of isolated wetlands surrounding endorheic lakes. Ecological trends and human impacts identified herein underscore the importance of assessing flyway-scale change as our model depictions likely reflect new and emerging bottlenecks to continental migration.
Research Article| January 01, 1980 Lower Paleozoic metasedimentary rocks in the east-central Sierra Nevada, California: Correlation with Great Basin formations J. N. MOORE; J. N. MOORE 1Department of Geology, University of Montana, Missoula, Montana 59812 Search for other works by this author on: GSW Google Scholar C. T. FOSTER, JR. C. T. FOSTER, JR. 2Department of Geology, The University of Iowa, Iowa City, Iowa 52242 Search for other works by this author on: GSW Google Scholar Author and Article Information J. N. MOORE 1Department of Geology, University of Montana, Missoula, Montana 59812 C. T. FOSTER, JR. 2Department of Geology, The University of Iowa, Iowa City, Iowa 52242 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1980) 91 (1): 37–43. https://doi.org/10.1130/0016-7606(1980)91<37:LPMRIT>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation J. N. MOORE, C. T. FOSTER; Lower Paleozoic metasedimentary rocks in the east-central Sierra Nevada, California: Correlation with Great Basin formations. GSA Bulletin 1980;; 91 (1): 37–43. doi: https://doi.org/10.1130/0016-7606(1980)91<37:LPMRIT>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Rock type, stratigraphic sequence, and associated fossils in metamorphic rocks exposed in roof pendants near Big Pine and Bishop, California, allow, for the first time, detailed correlation of Sierran metasedimentary rocks with Paleozoic formations in the Great Basin. The Big Pine pendant rocks are correlative with the Lower Cambrian Poleta Formation and represent shelf facies. Rocks of the eastern Bishop Creek pendant also represent predominantly shelf facies, and correlate with Ordovician and Silurian strata of the Inyo Range. These correlations place the early Paleozoic shelf margin west or northwest of the Bishop Creek pendant; they indicate that major structural features do not exist between the Sierra Nevada and the Great Basin at this latitude and substantiate the model that depicts these rocks as Cordilleran miogeoclinal strata. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Abstract. Local topographically driven processes – such as wind drifting, avalanching, and shading – are known to alter the relationship between the mass balance of small cirque glaciers and regional climate. Yet partitioning such local effects from regional climate influence has proven difficult, creating uncertainty in the climate representativeness of some glaciers. We address this problem for Sperry Glacier in Glacier National Park, USA, using field-measured surface mass balance, geodetic constraints on mass balance, and regional climate data recorded at a network of meteorological and snow stations. Geodetically derived mass changes during 1950–1960, 1960–2005, and 2005–2014 document average mass change rates during each period at −0.22 ± 0.12, −0.18 ± 0.05, and −0.10 ± 0.03 m w.e. yr−1, respectively. A correlation of field-measured mass balance and regional climate variables closely (i.e., within 0.08 m w.e. yr−1) predicts the geodetically measured mass loss from 2005 to 2014. However, this correlation overestimates glacier mass balance for 1950–1960 by +1.20 ± 0.95 m w.e. yr−1. Our analysis suggests that local effects, not represented in regional climate variables, have become a more dominant driver of the net mass balance as the glacier lost 0.50 km2 and retreated further into its cirque.
Before and during the first week of the March-April 1980 eruptions of Mount St. Helens, Washington, infrared thermal surveys were conducted to monitor the thermal activity of the volcano. The purpose was to determine if an increase in thermal activity had taken place since an earlier airborne survey in 1966. Nine months before the eruption there was no evidence of an increase in thermal activity. The survey during the first week of the 1980 eruptions indicated that little or no change in thermal activity had taken place up to 4 April. Temperatures of ejected ash and steam were low and never exceeded 15 degrees C directly above the vent.
Abstract. Local topographically driven processes such as wind drifting, avalanching, and shading, are known to alter the relationship between the mass balance of small cirque glaciers and regional climate. Yet partitioning such local effects apart from regional climate influence has proven difficult, creating uncertainty in the climate representativeness of some glaciers. We address this problem for Sperry Glacier in Glacier National Park, USA using field-measured surface mass balance, geodetic constraints on mass balance, and regional climate data recorded at a network of meteorological stations. Geodetically derived mass changes between 1950–1960, 1960–2005, and 2005–2014 document average mass loss rates during each period at −0.22±0.12 m w.e. yr−1, −0.18±0.05 m w.e. yr−1, and −0.10±0.03 m w.e. yr−1. A correlation of field-measured mass balance and regional climate variables closely predicts the geodetically measured mass loss from 2005–2014. However, this correlation overestimates glacier mass balance for 1950–1960 by +1.18±0.92 m w.e. yr−1. This suggests that local effects, not represented in regional climate variables, have become a more dominant driver of the net mass balance as the glacier lost 0.50 km2 and retreated further into its cirque.
