J. R. Mioduszewski

Understanding Greenland ice sheet hydrology using an integrated multi-scale approach

Improved understanding of Greenland ice sheet hydrology is critically important for assessing its impact on current and future ice sheet dynamics and global sea level rise. This has motivated the collection and integration of in situ observations, model development, and remote sensing efforts to quantify meltwater production, as well as its phase changes, transport, and export. Particularly urgent is a better understanding of albedo feedbacks leading to enhanced surface melt, potential positive feedbacks between ice sheet hydrology and dynamics, and meltwater retention in firn. These processes are not isolated, but must be understood as part of a continuum of processes within an integrated system. This letter describes a systems approach to the study of Greenland ice sheet hydrology, emphasizing component interconnections and feedbacks, and highlighting research and observational needs.

Atmospheric drivers of Greenland surface melt revealed by self‐organizing maps

Recent acceleration in surface melt on the Greenland ice sheet (GrIS) has occurred concurrently with a rapidly warming Arctic and has been connected to persistent, anomalous atmospheric circulation patterns over Greenland. To identify synoptic setups favoring enhanced GrIS surface melt and their decadal changes, we develop a summer Arctic synoptic climatology by employing self-organizing maps. These are applied to daily 500 hPa geopotential height fields obtained from the Modern Era Retrospective Analysis for Research and Applications reanalysis, 1979–2014. Particular circulation regimes are related to meteorological conditions and GrIS surface melt estimated with outputs from the Modele Atmospherique Regional. Our results demonstrate that the largest positive melt anomalies occur in concert with positive height anomalies near Greenland associated with wind, temperature, and humidity patterns indicative of strong meridional transport of heat and moisture. We find an increased frequency in a 500 hPa ridge over Greenland coinciding with a 63% increase in GrIS melt between the 1979–1988 and 2005–2014 periods, with 75.0% of surface melt changes attributed to thermodynamics, 17% to dynamics, and 8.0% to a combination. We also confirm that the 2007–2012 time period has the largest dynamic forcing relative of any period but also demonstrate that increased surface energy fluxes, temperature, and moisture separate from dynamic changes contributed more to melt even during this period. This implies that GrIS surface melt is likely to continue to increase in response to an ever warmer future Arctic, regardless of future atmospheric circulation patterns.

Controls on Spatial and Temporal Variability in Northern Hemisphere Terrestrial Snow Melt Timing, 1979–2012

AbstractSpring snowmelt onset has occurred earlier across much of the Northern Hemisphere land area in the last four decades. Understanding the mechanisms driving spring melt has remained a challenge, particularly in its spatial and temporal variability. Here, melt onset dates (MOD) obtained from passive microwave satellite data are used, as well as energy balance and meteorological fields from NASA’s Modern-Era Retrospective Analysis for Research and Applications, to assess trends in the MOD and attribute melt onset across much of Arctic and sub-Arctic Eurasia and North America during the spring snowmelt season from 1979 to 2012. Across much of the Northern Hemisphere MOD has occurred 1–2 weeks earlier over this period, with the strongest trends in western and central Russia and insignificant trends across most of North America. Trends in MOD are reflected by those in energy balance terms, with energy advection providing an increasing proportion of melt energy in regions with the strongest MOD trends. En...

Attribution of snowmelt onset in Northern Canada

In the region of Earth most sensitive to climate change, spring snowmelt serves as a measurable indicator of climate change and plays a strong role in the feedbacks that amplify Arctic warming. We characterize the melt season and attribute melt onset in a region of northern Canada during the spring snowmelt season from 2003 to 2011. Melt onset dates are obtained from Advanced Microwave Scanning Radiometer for the Earth Observing System retrievals. Energy balance and meteorological fields are obtained from NASAs Modern Era Retrospective Analysis for Research and Applications product. Analysis of three distinct subregions demonstrates that typical values of energy balance terms vary across the region and have different roles in melt attribution. Melt is controlled more by advective energy farther southwest where melt onset begins sooner, compared to higher levels of radiative energy over the tundra. This study demonstrates that a relatively small region can exhibit large differences in controls on spring snowmelt both within the region and interannually, and these differences can be understood in the context of factors ranging from the large-scale synoptic pattern to land cover and the local energy balance. Being able to attribute melt onset to those drivers that are changing as the high latitudes warm as opposed to those that do not (i.e., insolation) allows better long-term prediction of melt season dynamics and the climatological processes influenced by snow cover and its feedbacks.

In­situ monitoring of trace gases in a non-urban environment

Abstract A set of commercial instruments measuring carbon monoxide (CO), ozone (O 3 ), sulfur dioxide (SO 2 ), and nitrogen oxides [nitric oxide (NO), nitrogen dioxide (NO 2 ), and odd nitrogens (NO X )] was integrated and deployed in a non– urban environment. The deployment occurred between July 2, 2007 and August 7, 2007 in Richland, WA. The mixing ratios of all species were lower than in most rural–suburban environments, and strong diurnal patterns were observed. NO 2 was depleted by photochemically formed ozone during the day and replenished at night as ozone was destroyed. The highest ozone concentration during these episodes was 45 ppb. The overall average was 15 ppb with readings approaching near zero at times. This observation is low compared to average daytime summer readings of 60–80 ppb in highly populated and industrialized urban areas in the Pacific Northwest region. Back-trajectory analysis and prevailing weather conditions both indicated that much of the ozone was transported locally or was produced in– situ . Analysis of SO 2 as a tracer for O 3 advection further indicated lack of long–range regional transport of pollutants to Richland. We also present results of analysis of high ozone episodes and comparisons relative to other areas in the Pacific Northwest region. These results provide a useful sample data set to study the historical record of air quality in rural Eastern Washington.

Diminishing Arctic Sea Ice Promotes Stronger Surface Winds

AbstractProjections of Arctic sea ice through the end of the twenty-first century indicate the likelihood of a strong reduction in ice area and thickness in all seasons, leading to a substantial th...

Breaking the ice: Theorizing the mechanisms of Arctic thaw

Breaking the Ice: Theorizing the Arctic Thaw;New Brunswick, New Jersey, 12–14 April 2012 Some of the most striking contemporary environmental changes are the warming of the Arctic region and increased mass loss from the Greenland ice sheet. For example, areas of summer melt atop Greenlands massive ice sheet continue to expand, sending large volumes of ice and meltwater into surrounding seas and oceans. This may have profound implications for regional hydrology and marine biogeochemical cycles, as well as global sea level rise. While these trends are readily observable, urgent questions regarding how the Greenland ice sheet will respond to future climate change remain unanswered.