Steven W. Hostetler

United States Geological Survey | USGS

We apply the Community Ice Sheet Model (CISM2) to determine the extent to which the Last Glacial Maximum (LGM) temperature and precipitation climatologies from the Paleoclimate Modelling Intercomparison Project 3 (PMIP3) simulations support the large North American ice sheets that were prescribed as a boundary condition. We force CISM2 with eight P...

We assess monthly temperature and precipitation data derived by six statistically downscaled data sets for 14 general circulation models (GCMs) from the Climate Model Intercomparison Program Phase 5. We use a simple monthly water balance model to quantify and decompose uncertainties associated with the GCMs and statistical techniques in projections...

We analyze climate simulations conducted with the RegCM3 regional climate model on 50- and 15-km model grids to diagnose the dependence of wildfire incidence and area burned variations on monthly climate long-term means and anomalies over North America for the period 1986-2013. We created a new wildfire database by merging the Fire Program Analysis...

This study presents a synthesis of century-scale hydroclimate variations in North America for the Common Era (last 2000 years) using new age models of previously published multiple proxy-based paleoclimate data. This North American Hydroclimate Synthesis (NAHS) examines regional hydroclimate patterns and related environmental indicators, including...

Thermal regimes are fundamental determinants of aquatic ecosystems, which makes description and prediction of temperatures critical during a period of rapid global change. The advent of inexpensive temperature sensors dramatically increased monitoring in recent decades, and although most monitoring is done by individuals for agency-specific purpose...

Despite elevated summer insolation forcing during the early Holocene, global ice sheets retained nearly half of their volume from the Last Glacial Maximum, as indicated by deglacial records of global mean sea level (GMSL). Partitioning the GMSL rise among potential sources requires accurate dating of ice-sheet extent to estimate ice-sheet volume. H...

We simulate the 1950-2010 water balance for the conterminous U.S. (CONUS) with a monthly water balance model (MWBM) using the 800-m Parameter-elevation Regression on Independent Slopes Model (PRISM) data set as model input. We employed observed snow and streamflow data sets to guide modification of the snow and potential evapotranspiration componen...

The Columbia River Littoral Cell (CRLC), a high-wave-energy littoral system, extends 160 km alongshore, generally north of the large Columbia River, and 10–15 km in across-shelf distance from paleo-beach backshores to about 50 m present water depths. Onshore drill holes (19 in number and 5–35 m in subsurface depth) and offshore vibracores (33 in nu...

Significance Many studies predict climate change will cause widespread extinctions of flora and fauna in mountain environments because of temperature increases, enhanced environmental variability, and invasions by nonnative species. Cold-water organisms are thought to be at particularly high risk, but most predictions are based on small datasets an...

Arctic land-cover changes induced by recent global climate change (e.g., expansion of woody vegetation into tundra and effects of permafrost degradation) are expected to generate further feedbacks to the climate system. Past changes can be used to assess our understanding of feedback mechanisms through a combination of process modeling and paleo-ob...

We have implemented the USGS National Climate Change Viewer (NCCV), which is an easy-to-use web application that displays future projections from global climate models over the United States at the state, county and watershed scales. We incorporate the NASA NEX-DCP30 statistically downscaled temperature and precipitation for 30 global climate model...

Arctic land-cover changes (e.g., expansion of woody vegetation into tundra and effects of permafrost degradation) that have been induced by recent global climate change are expected to generate further feedbacks to the climate system. Past changes can be used to assess our understanding of feedback mechanisms through a combination of process modell...

We apply GENMOM, a coupled atmosphere– ocean climate model, to simulate eight equilibrium time slices at 3000-year intervals for the past 21 000 years forced by changes in Earth–Sun geometry, atmospheric greenhouse gases (GHGs), continental ice sheets, and sea level. Simulated global cooling during the Last Glacial Maximum (LGM) is 3.8 • C and the...

We use the NCEP/NCAR Reanalysis (NCEP) and the MPI/ECHAM5 general circulation model to drive the RegCM3 regional climate model to assess the ability of the models to reproduce the spatiotemporal aspects of the Pacific-North American teleconnection (PNA) pattern. Composite anomalies of the NCEP-driven RegCM3 simulations for 1982–2000 indicate that t...

As host to one of the major continental-scale ice sheets, and with considerable spatial variability of climate related to its physiography and location, North America has experienced a wide range of climates over time. The aim of this chapter is to review the history of those climate variations, focusing in particular on the continental-scale clima...

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Massive volumes of data are being created as modeling centers from around the world finalize their submission of climate simulations for the Coupled Model Intercomparison Project, phase 5 (CMIP5), in preparation for the forthcoming Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5). Scientists, resource managers, and oth...

We combine large observed data sets and dynamically downscaled climate data to explore historic and future (2050-2069) stream temperature changes over the topographically diverse Greater Yellowstone Ecosystem (elevation range = 824 - 4,017 m). We link future stream temperatures with fish growth models to investigate how changing thermal regimes cou...

Bioclimatic models predict large reductions in native trout across the Rocky Mountains in the 21st century but lack details about how changes will occur. Through five case histories across the region, we explore how a changing climate has been affecting streams and the potential consequences for trout. Monitoring records show trends in temperature...

Understanding the factors associated with the current distribution of Yellowstone cutthroat trout is an imperative step in the design and implementation of future conservation and management strategies, particularly given emerging potential stressors associated with regional climate change. Despite substantial interagency effort to develop rangewid...

The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood because only a few findings with robust chronologies exist for Antarctic ice sheets. We developed a chronology for the Weddell Sea sector of the East Antarctic ice sheet that, combined with ages from other Antarct...

The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic Ice Sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates that the advance to and retreat from their maximum ext...

The Pacific-North American (PNA) teleconnection pattern has long been recognized as a robust feature of Northern Hemisphere atmospheric circulation, and more specifically represents the structure of the quasi-stationary wave field over the North Pacific and North America. The general circulation model (GCM), MPI/ECHAM5, and the high-resolution regi...

Changes in glacier mass balance reflect an integrated response to fluctuations in precipitation and surface energy balance resulting from climate change and variability. Alpine glaciers are particularly sensitive to such changes in climate, with response times measured from centennial to decadal time scales. Our understanding of the response of alp...

Increasing acceptance of Global Climate Model (GCM) projections that the Earth’s climate will continue to warm well into the middle of the 21st century has generated a plethora of climate change models for downscaling global forecasts to scales more relevant for managers. The diversity of approaches and the spatial and temporal variability in the f...

Understanding the factors associated with the current distribution of Yellowstone cutthroat trout is an imperative step in the design and implementation of future conservation and management strategies, particularly given emerging potential stressors associated with regional climate change. Despite substantial interagency effort to develop rangewid...

We are completing multi‐decade to multi‐century simulations of regional climate at on a 50 km grid over North America and a 15 km grid over Western and Eastern North America. Our goals are 1) to understand the nature of climate change and variability and how that is manifest in ecosystem and hydrological responses, 2) to evaluate the ability...

We present a new, non-flux corrected AOGCM, GENMOM, that combines the GENESIS version 3 atmospheric GCM (Global Environmental and Ecological Simulation of Interactive Systems) and MOM2 (Modular Ocean Model version 2) nominally at T31 resolution. We evaluate GENMOM by comparison with reanalysis products (e.g., NCEP2) and three models used in the IPC...

The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic Ice Sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates that the advance to and retreat from their maximum ext...

Changes in glacier size and volume reflect an integrated response to fluctuations in precipitation and surface energy balance resulting from climate change and variability. Alpine glaciers are particularly sensitive to such changes in climate, with response times measured from centennial to decadal time scales. Our understanding of the response of...

We present a new, non-flux corrected AOGCM, GENMOM, that combines the GENESIS version 3 atmospheric GCM (Global ENvironmental and Ecological Simulation of Interactive Systems) and MOM2 (Modular Ocean Model version 2). We evaluate GENMOM by comparison with reanalysis products (e.g., NCEP2) and eight models used in the IPCC AR4 assessment. The overal...

We present new 3He surface exposure ages on moraines and bedrock near the summit of Mauna Kea, Hawaii, which refine the age of the Mauna Kea Ice Cap during the Local Last Glacial Maximum (LLGM) and identify a subsequent fluctuation of the ice margin. The 3He ages, when combined with those reported previously, indicate that the local ice-cap margin...

Between Point Grenville, Washington, and Point Conception, California (1500 km distance) 21 dune fields record longshore transport in 20 littoral cells during the late Holocene. The direction of predominant littoral transport is established by relative positions of dune fields (north, central, or south) in 17 representative littoral cells. Dune fie...

We are using a regional climate model to conduct time-slice simulations of paleoclimate over North America, and comparing these with syntheses of paleoclimatic data to examine the performance of the regional modeling system and to diagnose the potential controls of the climatic variations recorded by the data. The base climate simulations are 50-ye...

A 1-dimensional surface energy balance model is applied to produce continuous simulations of daily lake evaporation of Upper Klamath Lake, Oregon (UKL) for the period 1950–2005. The model is implemented using observed data from land-based sites and rafts collected during 2005–2006. Progressively longer, temporally overlapping simulations are produc...

Climate change will potentially alter physical habitat availability for trout species (both native and nonnative) in the western USA, and ultimately affect population distribution and abundance in watersheds across the region. To understand the biological consequences of habitat alteration associated with climate change, we have developed models li...

We have produced 100 years of high-resolution climate simulations over North America for present conditions and under a doubling of atmospheric CO2 using the RegCM3 regional climate model. The model was run on a 50-km grid adopted by the North American Regional Climate Change Assessment Program (http://www.narccap.ucar.edu), with 23 vertical atmosp...

We simulate paleo ENSO variability using GENMOM, a non flux-corrected AOGCM comprised of the GENESIS V3.0 atmospheric model and the MOM2 ocean model. The model produces realistic present ENSO variability and characteristics comparable with similar models used in the 2007 IPCC AR4 assessment. Our model runs include 1000-yr equilibrium simulations fo...

This study aims to determine whether observed shifts in sediment source (indicated by bulk sediment 40Ar-39Ar and Nd isotopic tracers) at a northeast Pacific core site are in response to variations in river basin erosion or transport pathways of terrigenous sediment once it reaches the ocean. We synthesize geologic and climate model data sets to ev...

e have produced 100-yr equilibrium simulations over North America for present-day conditions and for a doubling of atmospheric CO2 using the RegCM3 regional climate model. The long simulations are being analyzed in an attempt to understand changes in the mean state and variability of climate, and to investigate responses related to ENSO. The model...

The Melting Is in the Details Global sea level rises and falls as ice sheets and glaciers melt and grow, providing an integrated picture of the changes in ice volume but little information about how much individual ice fields are contributing to those variations. Knowing the regional structure of ice variability during glaciations and deglaciations...

The growth of carbonate formations in caves (speleothems) is sensitive to changes in environmental conditions at the surface (temperature, precipitation and vegetation) and can provide useful paleoclimatic and paleoenvironmental information. We use 73(230)Th dates from speleothems collected from a cave in southwestern Oregon (USA) to constrain spel...

We simulate multi-decadal and multi-centennial ENSO variability using GENMOM, a non flux-corrected A/OGCM comprised of the GENESIS V3.0 atmospheric model and the MOM2 ocean model. The model produces realistic ENSO variability comparable with similar models used in the 2007 IPCC assessment. Long integrations of the model yield significant changes in...

1] We have developed a physically based, distributed surface energy balance model to simulate glacier mass balance under meteorological and climatological forcing. Here we apply the model to estimate summer ablation on South Cascade Glacier, Washington, for the 2004 and 2005 mass balance seasons. To arrive at optimal mass balance simulations, we in...

The temporal and spatial structure of 332 404 daily fire-start records from the western United States for the period 1986 through 1996 is illustrated using several complimentary visualisation techniques. We supplement maps and time series plots with Hovmöller diagrams that reduce the spatial dimensionality of the daily data in order to reveal the u...

A number of climate proxies indicate that a ~7-kyr oscillation occurred during Marine Isotope Stage (MIS) 3, of which change in the Atlantic meridional overturning circulation (AMOC) and attendant change in cross-equatorial ocean heat transport played an integral role. The timing of MIS-3 sea-level changes is clearly linked to this climate oscillat...

We have sampled glacially deposited boulders on several moraines associated with Pleistocene glacial advances On Mauna Kea, Hawaii. We retrieved ultramafic xenoliths on these boulders and have measured cosmogenic 3He concentrations in olivine and clinopyroxine mineral grains to obtain surface exposure ages. Our two oldest-dated moraines, stratigrap...

A total of ten upland dune sheets, totaling 245 km in combined length, have been investigated for their origin(s) along the Oregon coast (500 km in length). The ages of dune emplacement range from 0.1 to 103 ka based on radiocarbon (36 samples) and luminescence (46 samples) dating techniques. The majority of the emplacement dates fall into two peri...

Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of t...

We apply a physically based lake model to assess the response of North American lakes to future climate conditions as portrayed by the transient trace-gas simulations conducted with the Max Planck Institute (ECHAM4) and the Canadian Climate Center (CGCM1) atmosphere-ocean general circulation models (A/OGCMs). To quantify spatial patterns of lake re...

A number of climate proxies indicate that an ˜7-kyr oscillation occurred during Marine Isotope Stage (MIS) 3, of which change in the Atlantic meridional overturning circulation (AMOC) and attendant change in cross-equatorial ocean heat transport played an integral role. The timing of Heinrich events and sea-level changes are clearly linked to this...

Paleoclimate records from glacial Indian and Pacific Ocean sediments document millennial-scale fluctuations of subsurface oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet, the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen...

The faunal and floral gradients that underlie the CLIMAP (1981) sea-surface temperature (SST) reconstructions for the Last Glacial Maximum (LGM) reflect ocean temperature gradients and frontal positions. The transfer functions used to reconstruct SSTs from biologic gradients are biased, however, because at the warmest sites they display inherently...

Site 1233 drilled during Leg 202 of the Ocean Drilling Program provides a detailed record of marine and continental climate change in the Southeast Pacific and South American continent. Splits from over 500 samples taken at 20 cm intervals for quantitative analysis of radiolarian and pollen populations yield a temporal resolution of 200–400 years....

The early Holocene transition from glacial to interglacial conditions that occurred ca. 13ka to 10ka in Beringia (eastern Siberia, Alaska, and northwestern Canada) was driven by the amplified seasonal cycle of northern hemisphere insolation and the accompanying changes in global ice volume, atmospheric composition, sea- surface temperature, and sea...

Estimating model uncertainty in a distributed glacier surface energy/mass balance model is difficult due to the large number of possible combinations of model parameter values. Here we address the issue of uncertainty in ablation submodels by examining model response to randomly selected values of seven key parameters (surface roughness lengths, pr...

The incidence of wildfire in the western United States is governed by climatological, meteorological, and ecological controls that operate across a range of spatial and temporal scales, from hemispheric to landscape, and from decadal (and longer) to diurnal. These controls are responsible for fire weather (i.e., the conditions responsible for the i...

This chapter explores the development of coupled climate and ice-sheet models over the past two decades, discusses the current technical and physical capabilities of models, and identifies future work for developing a better understanding of ice-climate events that have punctuated Earth history. The chapter also illustrates the complex behavior of...

The synthesis of paleoclimatic data sets and the simulation of past climates using climate models are a complimentary set of activities that lead to better understanding of the climate system. The objective of paleoclimate modeling is to quantify the behavior and variations of the components that describe the climate system. These components includ...

To assess the effects of regional biases in sea-surface temperature (SST) estimates on the climatology of the LGM we have conducted a suite of simulations with the GENESIS climate model in which the only changes from nominal LGM boundary conditions (continental ice, atmospheric composition, orbital parameters) are new SST fields. We compare four si...

The CLIMAP (1981) reconstructions of sea surface temperature (SST) of the Last Glacial Maximum (LGM) ocean have stimulated significant research and controversy. Some geochemical tracers, and the presence of glaciers in areas such as Hawaii and New Guinea, suggest that the CLIMAP SSTs may be biased in the tropics and subtropics. Here we assemble ava...

We use a combination of ice sheet modelling and regional climate modelling to explore the potential of freely arising (internally-driven) millennial climate variability due to ice sheet-ocean-atmosphere interactions in North America and the North Atlantic region. The last glacial cycle is simulated in North America using climate model snapshots for...

The incidence of wildfire in the western United States displays a strong seasonal cycle, related to climatically driven cycles of flammability and ignition. We illustrate here the seasonal cycle of wildfire and climate in the western United States using a combination of observed and simulated climate data sets, along with a daily data set consistin...

Large millennial-scale fluctuations of the southern margin of the North American Laurentide Ice Sheet occurred during the last deglaciation, when the margin was located between about 43 degrees and 49 degrees N. Fluctuations of the ice margin triggered episodic increases in the flux of freshwater to the North Atlantic by rerouting continental runof...

Anthropogenic desiccation of the Aral Sea between 1960 and the mid-1990s resulted in a substantial modification of the land surface that changed air temperature in the surrounding region. During the desiccation interval, the net annual rate of precipitation minus evaporation (P E) over the Aral Sea's surface became more negative by 15%, with the gr...

Model-derived equilibrium line altitudes (ELAs) of former tropical glaciers support arguments, based on other paleoclimate data, for both the magnitude and spatial pattern of terrestrial cooling in the tropics at the last glacial maximum (LGM). Relative to the present, LGM ELAs were maintained by air temperatures that were 3.5° to 6.6°C lower and p...

Bowen ratio meteorological stations have been deployed to measure rates of evaporation from groundwater discharge playas and from an adjacent vegetated bench in the Estancia Basin, in central New Mexico. The playas are remnants of late Pleistocene pluvial Lake Estancia and are discharge areas for groundwater originating as precipitation in the adja...

Eleven thousand years ago, large lakes existed in central and eastern North America along the margin of the Laurentide Ice Sheet. The large-scale North American climate at this time has been simulated with atmospheric general circulation models, but these relatively coarse global models do not resolve potentially important features of the mesoscale...

The CLIMAP project's reconstruction of past sea surface temperature inferred limited ice-age cooling in the tropical oceans. This conclusion has been controversial, however, because of the greater cooling indicated by other terrestrial and ocean proxy data. A new faunal sea surface temperature reconstruction, calibrated using the variation of foram...

Copyright 1999 by the American Geophysical Union The sensitivity of the tropics to climate change, particularly the amplitude of glacial-to-interglacial changes in sea surface temperature (SST), is one of the great controversies in paleoclimatology. Here we reassess faunal estimates of ice age SSTs, focusing on the problem of no-analog planktonic f...

Before coupled atmosphere-lake models can be used to study the response of large lake systems to climatic forcings, we must first evaluate how well they simulate the water balance and associated lake atmosphere interactions under present-day conditions. We evaluate the hydrology simulated by a lake model coupled to NCAR's regional climate model (Re...

We model the response o f the climate system during Heinrich event 2 (H2) by employing an atmospheric general circulation model, using boundary conditions based on the concept of a "canonical" Heinrich event. The canonical event is initialized with a full-height Laurentide ice sheet (LIS) and CLIMAP sea surface temperatures (SSTs), followed by lowe...

We apply a hierarchy of atmospheric and process models to assess the response in Western North America to a canonical North Atlantic Heinrich event that is characterized by lowering of the Laurentide Ice Sheet (LIS) and subsequent warming of North Atlantic sea surface temperatures (SSTs). Global responses to changes in the LIS and SSTs are simulate...

In a recent Forum piece that discusses climate variability ( Eos , December 16, 1997), S. F. Singer claims that “a higher CO 2 level may be less dangerous to the climate system than a lower one.” The basis for this reasoning is the observation that during the last Ice Age, CO 2 levels (∼200 ppmV) were lower than pre‐Industrial Revolution Holocene l...

Historical and geological data indicate that significant changes can occur in the Earth's climate on time scales ranging from years to millennia. In addition to natural climatic change, climatic changes may occur in the near future due to increased concentrations of carbon dioxide and other trace gases in the atmosphere that are the result of human...

We use a nested atmospheric modeling strategy to simulate precipitation and temperature of the western United States 18,000 years ago (18 ka). The high resolution of the nested model allows us to isolate the regional structure of summer temperature and winter precipitation that is crucial to determination of the net mass balance of late-Pleistocene...

Changes in precipitation and temperature regimes or patterns have significant potential effects on the distribution and abundance of plants and animals. For example, elevation of the timber-line is principally a function of temperature. Palaeolimnological investigations have shown significant shifts in phyto- and zoo-plankton populations as alpine...

Variability and unpredictability are characteristics of the aquatic ecosystems, hydrological patterns and climate of the largely dryland region that encompasses the Basin and Range, American Southwest and western Mexico. Neither hydrological nor climatological models for the region are suciently developed to describe the magnitude or direction of...

In this paper, we report on an experiment aimed at evaluating the feasibility of the application of our coupled regional climate modeling system to long-term climate simulations over the Great Lakes region. The simulation analyzed covers a continuous 24-month period beginning 1 September 1990 and extending to 1 September 1992. Many aspects of this...

The possible effects of trace-gas induced climatic changes on Pyramid and Yellowstone Lakes are assessed using a model of lake temperature. The model is driven by years of hourly meteorological data obtained directly from the output of double-CO2 experiments (2 × CO2) conducted with a regional climate model nested in a general circulation model. Th...

Lake systems continually respond to climatic conditions that vary over broad scales of space and time. The spatial distribution of lakes on the Earth’s surface is indicative of long-term patterns of atmospheric circulation, and the annual cycle of climate over lake basins is reflected in seasonal change in the size and temperature of lakes. Lake si...