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Amanda H. Lynch
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Maria Tsukernik and Amanda H. Lynch

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The Antarctic ice sheet constitutes the largest reservoir of freshwater on earth, representing tens of meters of sea level rise if it were to melt completely. However, because of the remote location of the continent and the concomitant sparse data coverage, much remains unknown regarding the climate variability in Antarctica and the surrounding Southern Ocean. This study uses the high-resolution ECMWF Interim Re-Analysis (ERA-Interim) data during 1979–2010 to calculate the meridional moisture transport associated with the mean circulation, planetary waves, and synoptic-scale systems. The resulting moisture flux, which is dominated by the synoptic scales, is largely consistent with results from theoretical assumptions and previous studies. Here, high interannual and regional variability in the total meridional moisture flux is found, with no significant trend over the last 30 years. Further, the variability of the meridional moisture flux cannot be explained by the southern annular mode or El Niño–Southern Oscillation, even in the Pacific sector. In addition, the Amundsen Sea sector experiences the highest variability in meridional moisture transport and reveals a statistically significant decrease in the moisture flux at synoptic scales along the coastal zone. These results suggest that the Amundsen Sea provides a window on the complex nature of atmospheric moisture transport in the high southern latitudes.

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Amanda H. Lynch and Wanli Wu

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Observations show that the amplitude of the annual atmospheric carbon dioxide cycle has increased. Lagged correlations between carbon dioxide, temperature, and vegetation suggest a modulation by ecosystem response, but the mechanisms remain unclear. Hypotheses include an early season uptake increase and/or winter respiration increase related to climate warming, and increased cycling in cooler conditions caused by disturbances such as fire. The first hypotheses suggest a positive feedback to regional warming, whereas the last suggests a negative feedback. Here it is shown that fire, as it influences species composition, can serve to enhance the increase in early season uptake but that a crucial determinant for the sign of the feedback is the impact of climate change on soil moisture.

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Amanda H. Lynch and Ronald D. Brunner

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Adaptive governance is a pattern that began to emerge from conflicts over natural resources in the American West a few decades ago. This was a pragmatic response to the emerging evidence that effective control was dispersed among multiple authorities and interest groups, that efficiency was only one of the many goals to be reconciled in policy decision processes, and that science itself was politically contested. Climate change as a policy problem exhibits many of these same features and has similarly led to gridlock in international and national forums. But humankind is not without guidance in securing the protection of life, limb, and livelihood in the face of environmental distress, particularly with regard to the challenge of adaptation. One effective analogy can be drawn to adaptations in the face of large climate variability such as El Niño. This paper compares adaptive governance with the tradition of scientific management in the international climate change regime, and it explores an example of adaptive governance in responding to the effects of a severe El Niño event in the Pacific islands. This event illustrates some of the specific kinds of human choices that will be made by those who are concerned about climate change as a policy problem. The basic choice is not scientific management or adaptive governance but continuing with business as usual or opening the frame to a wider range of possibilities.

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David A. Bailey and Amanda H. Lynch

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A coupled atmosphere–ice regional model previously used for simulations in the Arctic has been implemented in the Antarctic. Three 14-month simulations were performed for 1988–89, with different oceanic specifications. The year 1988 was interesting as there were several sensible heat polynya events in the Cosmonaut Sea region, the investigation of which is the goal of future finer-resolution simulations. Overall, the regional climate model produces reasonable simulations of the Antarctic at 100-km resolution. Root-mean-square errors range from 4 hPa in surface pressure, 4 K in near-surface air temperature, and 3 m s−1 in near-surface winds, to 1 K in air temperature and 2 m s−1 in winds at the 500-hPa level. Tests of the coupled system response to oceanic heat flux suggest that the sea-ice simulation is more sensitive than the atmospheric circulation, but it could be expected that the atmosphere would respond to these changes in sea ice over longer time periods than those of interest here. This sensitivity argues for the need for interactive ocean thermodynamics to successfully simulate Antarctic sea-ice distributions.

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Wanli Wu, Amanda H. Lynch, and Aaron Rivers

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There is a growing demand for regional-scale climate predictions and assessments. Quantifying the impacts of uncertainty in initial conditions and lateral boundary forcing data on regional model simulations can potentially add value to the usefulness of regional climate modeling. Results from a regional model depend on the realism of the driving data from either global model outputs or global analyses; therefore, any biases in the driving data will be carried through to the regional model. This study used four popular global analyses and achieved 16 driving datasets by using different interpolation procedures. The spread of the 16 datasets represents a possible range of driving data based on analyses to the regional model. This spread is smaller than typically associated with global climate model realizations of the Arctic climate. Three groups of 16 realizations were conducted using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) in an Arctic domain, varying both initial and lateral boundary conditions, varying lateral boundary forcing only, and varying initial conditions only. The response of monthly mean atmospheric states to the variations in initial and lateral driving data was investigated.

Uncertainty in the regional model is induced by the interaction between biases from different sources. Because of the nonlinearity of the problem, contributions from initial and lateral boundary conditions are not additive. For monthly mean atmospheric states, biases in lateral boundary conditions generally contribute more to the overall uncertainty than biases in the initial conditions. The impact of initial condition variations decreases with the simulation length while the impact of variations in lateral boundary forcing shows no clear trend. This suggests that the representativeness of the lateral boundary forcing plays a critical role in long-term regional climate modeling. The extent of impact of the driving data uncertainties on regional climate modeling is variable dependent. For some sensitive variables (e.g., precipitation, boundary layer height), even the interior of the model may be significantly affected.

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Amanda H. Lynch, Lee Tryhorn, and Rebecca Abramson

Efforts are being made to develop new paradigms for climate change adaptation policy at both the national and the international levels. However, progress in vulnerability and adaptation research has not been matched by advancement on practical policy initiatives. The complexity of the challenge to develop methods and means to support adaptation to climate change necessitates a diversity of approaches. This diversity is healthy, and yet it is possible to define some key characteristics and tools that can promote practical outcomes. In this paper, some methodologies that have proved successful are reviewed. These include a mapping of contextual circumstances, an appreciation for multiple perspectives, and the importance of a “boundary object” in forging strong interactions among project participants. Further, a toolkit of approaches for natural scientists is presented. This toolkit can be used to organize work in collaboration with stakeholders and other participants and can help overcome barriers to a meaningful contribution to the policy process. Fundamentally, this challenge will require approaches that are more grounded in meaning, narration, and reflection.

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David A. Bailey and Amanda H. Lynch

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In this, the second part of the analysis of an Antarctic regional climate system model, the model results and analyses are compared to a series of observational data from automated weather stations at a number of Antarctic stations, radiosonde launches, and surface energy balance climatology. The observational analyses show significant biases in comparison with station data, which is attributable in part to the errors in and low resolution of the elevation dataset. This is a factor in model performance also. Further, a dominant factor in the generation of the model biases is the simulation of atmospheric water vapor and cloud. The known “cold” bias in the clear-sky longwave radiation scheme is amply compensated for by excessive cloudiness in many cases. The strong vertical moisture transport contributes to the excessive cloud formation. The biases explored in detail in this paper are common to regional and global simulations of the Antarctic region and highlight areas in which model development should be concentrated, particularly in coupled models with greater degrees of freedom.

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Lance M. Leslie, Greg J. Holland, and Amanda H. Lynch

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A series of numerical modeling simulations are made of the type 2 east-coast cyclone described in Holland et al. The aims are (i) to show that this mesoscale development can be successfully forecast from initial synoptic scale data and (ii) to diagnose the relative roles of large-scale processes, convection, topography, and surface fluxes in producing this development. We show that the development can be forecast successfully with the current Australian limited-area prediction model, but that high resolution is needed to capture fully the intensity, structure and track of the system.

We show also that both large- and small-scale processes contribute to the development of the east-coast cyclone. Large-scale moist baroclinic processes provide the favorable environment and initial development of a weak, synoptic-scale cyclone. Subsequent development of the intense, mesoscale system requires convective release of latent heat, local orographic forcing, and high resolution surface energy fluxes.

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Mark C. Serreze, Amanda H. Lynch, and Martyn P. Clark

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Calculations of a thermal front parameter using NCEP–NCAR reanalysis data over the period 1979–98 reveal a relative maximum in frontal frequencies during summer along northern Eurasia from about 60° to 70°N, best expressed over the eastern half of the continent. A similar relative maximum is found over Alaska, which is present year-round although best expressed in summer. These high-latitude features can be clearly distinguished from the polar frontal zone in the midlatitudes of the Pacific basin and collectively resemble the summertime“Arctic frontal zone” discussed in several early studies. While some separation between high- and midlatitude frontal activity is observed in all seasons, the summer season is distinguished by the development of an attendant mean baroclinic zone aligned roughly along the Arctic Ocean coastline and associated wind maxima in the upper troposphere. The regions of maximum summer frontal frequency correspond to preferred areas of cyclogenesis and to where the summertime contribution to annual precipitation is most dominant. Cyclones generated in association with the Eurasian frontal zone often track into the central Arctic Ocean, where they may have an impact on the sea-ice circulation. Development of the summertime Eurasian frontal zone and the summertime strengthening of the Alaskan feature appear to be largely driven by differential heating between the cold Arctic Ocean and warm snow-free land. Frontal activity also shows an association with orography. Several studies have argued that the location of the summer Arctic frontal zone may be in part determined by discontinuities in energy exchange along the tundra–boreal forest boundary. While such a linkage is not discounted here, a vegetation forcing is not required in this conceptual model.

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