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Geology topics

Thomas G. Huntington

Publications and source records attributed to Thomas G. Huntington.

At least 55 records · Page 3Linked to original sources
USGS2010

Climate warming-induced intensification of the hydrologic cycle: A review of the published record and assessment of the potential impacts on agriculture

Climate warming is expected to intensify and accelerate the global hydrologic cycle resulting in increases in evaporation, evapotranspiration (ET), atmospheric water-vapor content, and precipitation. The strength of the hydrologic response, or sensitivity of the response for a given degree of warming, is a critical outstanding question in climatology and hydrology. In this review chapter, I examine the published record of trends in various components of the hydrologic cycle and associated variables to assess observed hydrologic responses to warming during the period of observational records. Global and regional trends in evaporation, ET, and atmospheric water-vapor content and several large river basin water-balance studies support an ongoing intensification of the hydrologic cycle. Global trends in precipitation, runoff, and soil moisture are more uncertain than the trends in the variables noted above, in part because of high spatial and temporal variability. Trends in associated variables, such as systematic changes in ocean salinity, the length of the growing season, and the rate of precipitation recycling are generally consistent with intensification of the hydrologic cycle. The evidence for an increase in the frequency, intensity, or duration of extreme-weather events like hurricanes is mixed and remains uncertain. The largest potential impacts to agricultural systems depend greatly on the responses of hydrologic variables that are the most uncertain; for example, intensity and duration of heavy rainfall events; frequency, intensity, and duration of major storms and droughts; and rates of erosion. Impacts on agriculture will depend greatly on how insects, diseases, weeds, nutrient cycling, effectiveness of agrichemicals, and heat stress are affected by an intensification of the hydrologic cycle.

Advances in Agronomy↗
USGS2009

Climate and hydrological changes in the northeastern United States: recent trends and implications for forested and aquatic ecosystems

We review twentieth century and projected twenty-first century changes in climatic and hydrologic conditions in the northeastern United States and the implications of these changes for forest ecosystems. Climate warming and increases in precipitation and associated changes in snow and hydrologic regimes have been observed over the last century, with the most pronounced changes occurring since 1970. Trends in specific climatic and hydrologic variables differ in their responses spatially (e.g., coastal vs. inland) and temporally (e.g., spring vs. summer). Trends can differ depending on the period of record analyzed, hinting at the role of decadal-scale climatic variation that is superimposed over the longer-term trend. Model predictions indicate that continued increases in temperature and precipitation across the northeastern United States can be expected over the next century. Ongoing increases in growing season length (earlier spring and later autumn) will most likely increase evapotranspiration and frequency of drought. In turn, an increase in the frequency of drought will likely increase the risk of fire and negatively impact forest productivity, maple syrup production, and the intensity of autumn foliage coloration. Climate and hydrologic changes could have profound effects on forest structure, composition, and ecological functioning in response to the changes discussed here and as described in related articles in this issue of the Journal.

Connecticut, Maine, Massachusetts, New Hampshire, ↗
USGS2008

Can we dismiss the effect of changes in land‐based water storage on sea‐level rise?

The rate of global mean sea-level rise (SLR) during the 20th century is estimated to be 1.7 mm yr −1 ±0.3 yr −1 (Church and White, 2006). SLR during the 20th century was a result of thermal expansion of the oceans and the release of water from terrestrial storage reservoirs (Bindoff et al ., 2007). The latter process is thought to be dominated by the melting of glaciers and polar ice caps, but human alterations to the landscape and climate-change driven feedbacks may also affect land-based water storage (Gornitz et al ., 1997; Mitrovica et al ., 2001; Bindoff et al ., 2007). Estimates of the amount of SLR that can be explained by the combination of thermosteric effects and the melting of ice and snow consistently underestimate SLR determined from observations based on tide gages and satellite altimetry (Gornitz et al ., 1997; Church et al .,2001; Miller and Douglas, 2004; Lombard et al ., 2006; Bindoff et al .,2007). Refinements in estimates of changes in volumes of land ice and thermosteric effects have reduced the component of SLR that remains unexplained between the Intergovernmental Panel on Climate Change third assessment (Church et al ., 2001) and current estimates (Lombard et al ., 2006). Anthropogenic alterations that result in or imply net land-to-ocean transfers include groundwater depletion (GWD), sedimentation in reservoirs, wetland loss, surface water depletion (SWD), and deforestation. GWD occurs when the rate of withdrawal exceeds the rate of recharge over decadal time scales (Sahagian, 2000; Konikow and Kendy, 2005).SWD occurs when the rate of withdrawal from rivers, lakes or impound-ments exceeds natural inputs to these water bodies (Falkenmark andLannerstad, 2005; Haddeland et al., 2006). There are also indirect effects of human alterations of the landscape, such as deforestation and desertification that can affect local or regional precipitation and, ultimately, reduce recharge and decrease water storage in soils and underlying aquifers (Wang and Eltahir, 2000). Anthropogenic or climate-driven changes in land use can affect albedo and alter energy and water budgets resulting in changes in soil moisture storage. Climate feedbacks can also alter terrestrial water balance (Milly et al ., 2003) and hydrologic conditions in permafrost environments (Hinzman et al ., 2005). Anthropogenicalterations that result in ocean-to-land transfers include reservoir construction for surface water storage and leakage of water impounded behind dams into underlying aquifers (Vorosmarty and Sahagian, 2000).

Hydrological Processes↗
USGS2007

Nutrient Enrichment in Estuaries from Discharge of Shallow Ground Water, Mt. Desert Island, Maine

Nutrient enrichment from atmospheric deposition, agricultural activities, wildlife, and domestic sources is a concern at Acadia National Park because of the potential problem of water-quality degradation and eutrophication in its estuaries. Water-quality degradation has been observed at the Park?s Bass Harbor Marsh estuary but not in Northeast Creek estuary. Previous studies at Acadia National Park have estimated nutrient inputs to estuaries from atmospheric deposition and surface-water runoff, but the importance of shallow ground water that may contain nutrients derived from domestic or other sources is unknown. Northeast Creek and Bass Harbor Marsh estuaries were studied to (1) identify shallow ground-water seeps, (2) assess the chemistry of the water discharged from selected seeps, and (3) assess the chemistry of ground water in shallow ground-water hyporheic zones. The hyporheic zone is defined here as the region beneath and lateral to a stream bed, where there is mixing of shallow ground water and surface water. This study also provides baseline chemical data for ground water in selected bedrock monitoring wells and domestic wells on Mt. Desert Island. Water samples were analyzed for concentrations of nutrients, wastewater compounds, dissolved organic carbon, pH, dissolved oxygen, temperature and specific conductance. Samples from bedrock monitoring wells also were analyzed for alkalinity, major cations and anions, and trace metals. Shallow ground-water seeps to Northeast Creek and Bass Harbor Marsh estuaries at Acadia National Park were identified and georeferenced using aerial infrared digital imagery. Monitoring included the deployment of continuously recording temperature and specific conductance sensors in the seep discharge zone to access marine or freshwater signatures related to tidal flooding, gradient-driven shallow ground-water flow, or shallow subsurface flow related to precipitation events. Many potential shallow ground-water discharge zones were identified from aerial thermal imagery during flights in May and December 2003 in both estuaries. The occurrence of ground-water seeps was confirmed using continuous and discrete measurements of temperature and specific conductance in selected seeps and in the adjacent estuaries that showed salinity anomalies reflecting the input of freshwater in these complex tidal systems. Analysis of water samples from shallow ground water in the hyporheic zone and from ground-water seeps indicated the presence of elevated concentrations of dissolved nitrogen, compared to concentrations in the adjacent estuaries and surface-water tributaries draining into the estuaries. These findings indicate that shallow ground water is a source of dissolved nitrogen to the estuaries. Orthophosphate levels were low in ground water in the hyporheic zone in Bass Harbor Marsh, but somewhat higher in one hyporheic-zone well in Northeast Creek compared with the concentrations in both estuaries that were at or below detection limits. Household wastewater-related compounds were not detected in ground water in the hyporheic zone. Analysis of water samples from domestic and bedrock monitoring wells developed in fractured bedrock indicated that concentrations of dissolved nitrogen, phosphorus, and household wastewater-related compounds were typically at or below detection, suggesting that the aquifers sampled had not been contaminated from septic sources.

Scientific Investigations Report↗
USGS2006

Evidence for intensification of the global water cycle: Review and synthesis

One of the more important questions in hydrology is: if the climate warms in the future, will there be an intensification of the water cycle and, if so, the nature of that intensification? There is considerable interest in this question because an intensification of the water cycle may lead to changes in water-resource availability, an increase in the frequency and intensity of tropical storms, floods, and droughts, and an amplification of warming through the water vapor feedback. Empirical evidence for ongoing intensification of the water cycle would provide additional support for the theoretical framework that links intensification with warming. This paper briefly reviews the current state of science regarding historical trends in hydrologic variables, including precipitation, runoff, tropospheric water vapor, soil moisture, glacier mass balance, evaporation, evapotranspiration, and growing season length. Data are often incomplete in spatial and temporal domains and regional analyses are variable and sometimes contradictory; however, the weight of evidence indicates an ongoing intensification of the water cycle. In contrast to these trends, the empirical evidence to date does not consistently support an increase in the frequency or intensity of tropical storms and floods.

Journal of Hydrology↗
USGS2006

Using optical proxies for biogeochemical properties to study land coverage and terrestrial inputs of organic carbon into coastal waters from the Penobscot Watershed to the Gulf of Maine

Coastal waters are physically, biogeochemically, and therefore optically complex as a result of the commingling of waters arising from terrestrial, freshwater and marine ecosystems. Separating the influences of these three ecosystems on the optical properties of the resulting mixture is challenging, particularly given the variability within each. The longterm goals of this project are twofold: (1) to investigate the feasibility of identifying landuse changes using inwater optical observations, (2) to quantify the input of terrestrial organic carbon into the coastal marine environment. Our approach is to study the Penobscot River Watershed in Maine, from its many tributaries and subwatersheds into the main branch of the Penobscot River, Penobscot Bay and ultimately into the coastal waters of the Eastern Maine Coastal Current. The first step towards this goal is to define optical signatures associated with specific watershed land coverages measured at the source (optical proxies). The next step is to track those proxies from their respective sources to the coast, characterizing the dilution and transformative processes. Using analyses of discrete samples collected monthly from the subwatersheds, we have quantified optical proxies for both dissolved and particulate organic carbon, particulate carbon to nitrogen ratios and fluorophores unique to certain land coverages (e.g. wetlands, residence ponds, lumber mills, agriculture). We apply these proxies to in situ optical observations retrieved from sensors moored within the lower river and upper estuary to quantify the temporal patterns in the biogeochemical properties. To date we have approximately 2 years of observations, including the wettest year on record for the last century in this region. The proxies associated with the dissolved fraction are the most robust and provide signatures for both land coverage and for organic carbon concentration. Those associated with particles are robust proxies for carbon but are less informative about land coverage.

Maine↗
USGS2005

Summer low flows in New England during the 20th Century

High springtime river flows came earlier by one to two weeks in large parts of northern New England during the 20th Century. In this study it was hypothesized that late spring/early summer recessional flows and late summer/early fall low flows could also be occurring earlier. This could result in a longer period of low flow recession and a decrease in the magnitude of low flows. To test this hypothesis, variations over time in the magnitude and timing of low flows were analyzed. To help understand the relation between low flows and climatic variables in New England, low flows were correlated with air temperatures and precipitation. Analysis of data from 23 rural, unregulated rivers across New England indicated little evidence of consistent changes in the timing or magnitude of late summer/early fall low flows during the 20th Century. The interannual variability in the timing and magnitude of the low flows in northern New England was explained much more by the interannual variability in precipitation than by the interannual variability of air temperatures. The highest correlation between the magnitude of the low flows and air temperatures was with May through November temperatures (r =−0.37, p = 0.0017), while the highest correlation with precipitation was with July through August precipitation (r = 0.67, p > 0.0001).

Connecticut, Maine, Massachusetts, New Hampshire, ↗