Tundra water budget and implications of precipitation underestimation

Difficulties in obtaining accurate precipitation measurements have limited meaningful hydrologic assessment for over a century due to performance challenges of conventional snowfall and rainfall gauges in windy environments. Here, we compare snowfall observations and bias adjusted snowfall to end-of-winter snow accumulation measurements on the ground for 16 years (1999–2014) and assess the implication of precipitation underestimation on the water balance for a low-gradient tundra wetland near Utqiagvik (formerly Barrow), Alaska (2007–2009). In agreement with other studies, and not accounting for sublimation, conventional snowfall gauges captured 23–56% of end-of-winter snow accumulation. Once snowfall and rainfall are bias adjusted, long-term annual precipitation estimates more than double (from 123 to 274 mm), highlighting the risk of studies using conventional or unadjusted precipitation that dramatically under-represent water balance components. Applying conventional precipitation information to the water balance analysis produced consistent storage deficits (79 to 152 mm) that were all larger than the largest actual deficit (75 mm), which was observed in the unusually low rainfall summer of 2007. Year-to-year variability in adjusted rainfall (±33 mm) was larger than evapotranspiration (±13 mm). Measured interannual variability in partitioning of snow into runoff (29% in 2008 to 68% in 2009) in years with similar end-of-winter snow accumulation (180 and 164 mm, respectively) highlights the importance of the previous summer's rainfall (25 and 60 mm, respectively) on spring runoff production. Incorrect representation of precipitation can therefore have major implications for Arctic water budget descriptions that in turn can alter estimates of carbon and energy fluxes

Active layer hydrology for Imnavait Creek, Toolik, Alaska

The hydrology of the active layer of a watershed is described. In the annual hydrologic cycle, snowmelt is the most significant event at Imnavait Creek located near Toolik Lake, Alaska. Precipitation that has accumulated for more than 6 months on the surface melts in a relatively short period of 7 to 10 days once sustained melting occurs. Significant runoff events are few. Convective storms covering relatively small areas on the North Slope of Alaska can produce significant small-scale events in a small watershed scale,but these events are rapidly attenuated outside the basin. Data collection began in August 1984. We have continuously monitored the hydrologic, the meteorologic, and the soil's physical conditions. Information was collected through implementation of four snowmelt runoff plots and measurements of essential microclimate parameters. Soil moisture and temperature profiles were measured adjacent to each snowmelt runoff plot, and heat flux is collected adjacent to one of these plots. Meteorological parameters were measured locally. The water content of the snowpack prior to snowmelt was measured throughout the watershed and measured daily adjacent to each plot during snowmelt. The stream draining the basin was measured regularly during the spring melt event to provide information on watershed runoff rates and the volume of snowmelt

Arctic Report Card 2007: Tracking Recent Environmental Changes

Collectively, the observations indicate that the overall warming of the Arctic system continued in 2007. There are some elements that are stabilizing or returning to climatological norms. These mixed tendencies illustrate the sensitivity and complexity of the Arctic System. Atmosphere: Hot spot shifts toward Europe Ocean: North Pole Temperatures at depth returning to 1990s values Sea Ice: Summer extent at record minimum Greenland: Recent warm temperatures associated with net ice loss Biology: increasing tundra shrub cover and variable treeline advance; up to 80% declines in some caribou herds while goose populations double Land: Increase in permafrost temperatures The Arctic Report Card 2007 is introduced as a means of presenting clear, reliable and concise information on recent observations of environmental conditions in the Arctic, relative to historical time series records. It provides a method of updating and expanding the content of the State of the Arctic Report, published in fall 2006, to reflect current conditions. Material presented in the Report Card is prepared by an international team of scientists and is peer-reviewed by topical experts nominated by the US Polar Research Board. The audience for the Arctic Report Card is wide, including scientists, students, teachers, decision makers and the general public interested in Arctic environment and science. The web-based format will facilitate future timely updates of the content

Paleoclimate, Paleoclimate history of the Arctic

Although the Arctic occupies less than 5% of the Earth's surface, it includes some of the strongest positive feedbacks in the climate system. Reconstructing the climate history of the Quaternary requires a suite of climate proxies that can be placed in a secure time frame. Most Arctic proxies reflect past summer temperatures, although a subset is sensitive to winter temperatures and/or precipitation. During the Quaternary, the Arctic has experienced a greater change in temperature, vegetation, and ocean surface characteristics than has any other Northern Hemisphere latitudinal band. Arctic temperature amplification is a consequence of several strong positive feedbacks. They include the fast feedbacks of snow and ice albedo, sea-ice insulation, vegetation, and permafrost, as well as a suite of slower responding feedbacks operating on glacial–interglacial timescales tied to the growth and decay of aerially extensive, thick continental ice sheets. Large changes in Arctic temperatures impact regions outside the Arctic through their proximal influence on the planetary energy balance and circulation of the Northern Hemisphere atmosphere and ocean, and with potential global impacts through changes in sea level, the release of greenhouse gases, and impacts on the ocean's meridional overturning circulation. Quantitative paleoclimate reconstructions for specific cold and warm times during the Quaternary suggest that Arctic temperature changes have been 3 to 4 times the corresponding hemispheric or globally averaged changes. This article provides a brief overview of climate changes leading up to the last ice age, then overviews the changes in Arctic climate during the Quaternary

Estimating Foliar Pigment Concentration of Rice Crop Using Integrated Hyperspectral Index

Part 1: GIS, GPS, RS and Precision FarmingInternational audiencePhotosynthetic pigment concentration has strong relationship with nitrogen (N) concentration which is an essential element of plant growth and plays an important role in estimating the net primary productivity (NPP) in terrestrial ecosystem research and precision agriculture (PA). In this study, hyperspectral reflectance and pigment concentration of the upper three leaves of rice crop (Oryza sativa L.) with five N fertilization rates were measured in the laboratory. The results showed that there was no significant difference between the leaf hyperspectral reflectance and pigment concentrations in the visible and near-infrared (NIR) spectral regions at each leaf position. But in the shortwave infrared (SWIR) region, the difference of each two of the three leaf positions was obviously significant at level 0.05. The integrated hyperspectral index MCARI/OSAVI[670,800] had been proved to be better linear related with leaf pigment concentrations at different leave position. The result demonstrated that MCARI/OSAVI[670,800] was a reliable and stable hyperspectral index for estimating pigment concentration at leaf level