On the identification of ENSO-induced rainfall and runoff variability: a comparison of methods and indices

Abstract

It is known that the El Niño Southern Oscillation (ENSO) phenomenon induces marked climate variability across many parts of the world. However, in seeking useful relationships between ENSO and climate, several indices are available. In addition to the choice of index, previous studies assessing ENSO effects have employed a range of different methods to classify periods as El Niño, La Niña or Neutral. It is therefore clear that significant subjectivity exists in the adoption of ENSO classification schemes. In this study, several ENSO classification methods are applied to a range of ENSO indices. Each method-index combination is investigated to determine which provides the strongest relationship with rainfall and runoff in the Williams River catchment, New South Wales, Australia. The results demonstrate substantial differences between the methods and indices. The Multivariate ENSO Index (or MEI) is found to provide the best classification irrespective of method. The potential for forecasting ENSO-related effects on rainfall, runoff and river abstractions is then investigated. A “rise rule” to account for dynamic ENSO trends is also assessed. Strong relationships were found to exist with runoff (rainfall) up to nine (eight) months in advance of the Summer/autumn period. Implications for improved forecasting of potential river abstractions are apparent.     

An early Holocene caribou antler from northern Ellesmere Island, Canadian Arctic Archipelago

During the last glaciation of northern Ellesmere Island many areas remained ice-free. A caribou antler from deglacial-marine sediments in Clements Markham Inlet dates 8,415 ± 135 B.P. (S-2501). If locally derived it places caribou at the northern limit of their contemporary range at the onset of deglaciation in this area. Immediately to the south, on the Hazen Plateau, ice remained at its limit until c . 8,000 B.P. Therefore, this antler may indicate the presence of caribou during full glacial time.     

10Be chronology of the last deglaciation of County Donegal, northwestern Ireland

A well-preserved moraine on the northern coast of County Donegal, Ireland, has played a critical role in our understanding of the glacial history of this sector of the Irish Ice Sheet (IIS). Because of a lack of numerical dating of the moraine, however, previous interpretations of its age and significance to the glacial history of this region have varied widely. Here we report eight in situ cosmogenic ¹⁰Be ages on boulders sampled from the moraine. Two of these ages are outliers, with the remaining six ranging from 18.8±1.0 ¹⁰Be kyr to 20.9±1.3 ¹⁰Be kyr, with an uncertainty-weighted mean age of 19.4±0.3 ¹⁰Be kyr (19.4±1.2 kyr accounting for production rate uncertainty). Our results confirm one previous ¹⁰Be age obtained from the moraine, with the combined data ( n =7) constraining the age of initial deglaciation of the IIS from its LGM position on the continental shelf to be 19.3±0.3 ¹⁰Be kyr (19.3±1.2 kyr accounting for production rate uncertainty). These ages are in excellent agreement with calibrated ¹⁴C ages that constrain retreat of the IIS margin from the continental shelf elsewhere in northwestern and western Ireland and the Irish Sea Basin associated with the start of the Cooley Point Interstadial (≥20–≤18.2 cal. kyr BP), suggesting widespread deglaciation of the IIS ∼19.5–20 kyr ago.     

NEW 10BE COSMOGENIC AGES FROM THE VIMMERBY MORAINE CONFIRM THE TIMING OF SCANDINAVIAN ICE SHEET DEGLACIATION IN SOUTHERN SWEDEN

The overall pattern of deglaciation of the southern part of the Scandinavian Ice Sheet has been considered established, although details of the chronology and ice sheet dynamics are less well known. Even less is known for the south Swedish Upland because the area was deglaciated mostly by stagnation. Within this area lies the conspicuous Vimmerby moraine, for which we have used the terrestrial cosmogenic nuclide (¹⁰Be) exposure dating technique to derive the exposure age of six glacially transported boulders. The six ¹⁰Be cosmogenic ages are internally consistent, ranging from 14.9 ± 1.5 to 12.4 ± 1.3 ka with a mean of 13.6 ±0.9 ka. Adjusting for the effects of surface erosion, snow burial and glacio-isostatic rebound causes the mean age to increase only by c. 6% to c. 14.4± 0.9 ka. The ¹⁰Be derived age for the Vimmerby moraine is in agreement with previous estimates forthe timing of deglaciation based on radiocarbon dating and varve chronology. This result shows promise for further terrestrial cosmogenic nuclide exposure studies in southern Sweden.     

From catfish to organic fish: making distinctions about nature as cultural economic practice

This paper addresses the cultural economy of nature and the material culture of economic practice. Attending to ways that cultural notions about the biophysical world play key roles in political economic conflicts, discussion centers on two recent debates involving the cultural economy of seafood production and trade. The first debate is over whether the label “catfish” should include catfish imported from Vietnam into the United States; the second deals with whether fish and shellfish should be eligible to be certified “organic” under new US regulations. Analysis reveals that the key dynamic in these debates is not necessarily how people think about “nature”, but instead is how people make distinctions about the world. Rather than focusing on what is natural or not, key actors make distinctions among both organisms and environments. The ways that different groups define and enclose the biophysical world works to distinguish places as either appropriate or not for certain kinds of production activities. The overall argument is that significance and meaning of the biophysical become implicated in economic geographies by making distinctions about the world that then become important for how economic activity can work. As such, cultural economic approaches should attend to the ways that the biophysical is involved in relations such as competition and international trade, while nature-society approaches should shift focus from Nature to specific aspects of the biophysical world.     

Spatial correlations between urbanization and river water pollution in the heavily polluted area of Taihu Lake Basin, China

Water pollution in the Taihu Lake Basin has been the focus of attention in China and abroad for a long time, due to its position in the forefront of urban development in China. Based on data gathering and processing from 84 monitoring sections in this heavily polluted area, this study first analyzes spatial patterns of urbanization and the distribution of river water pollution, and then uses the GeoDa bivariate spatial autocorrelation model to investigate the spatial correlation between urbanization and river water pollution at the scale of township units. The results show that urbanization has adverse impacts on water pollution, and the influence varies in different levels of development areas. The urban township units have the highest level of urbanization and highest pollution, but the best water quality; the suburban units have lower level of urbanization, but higher pollution and worse water quality; however the rural units have the lowest level of urbanization and lowest pollution, mainly affected by upstream pollution, but worst water quality. Lastly, urban and rural planning committees, while actively promoting the process of development in the region, should gradually resolve the issue of pollution control lagging behind urban life and urban develop- ment, giving priority to construction of centralized sewage treatment facilities and associated pipeline network coverage in the rural areas and suburban areas.     

A new perspective of the physical processes associated with the clear-sky greenhouse effect over high latitudes

The physical processes associated with the clear-sky greenhouse effect in the presence of water vaporare examined by including surface emissivity in the greenhouse effect formulation, and by introducing anew way to partition physical processes of the greenhouse effect. In this new framework, it is found thatthe clear-sky greenhouse effect is governed by three physical processes associated with (1) the temperaturecontrast between the surface and the atmosphere, (2) the interaction between the surface emissivity andthe temperature contrast, and (3) the surface emissivity. The importance of the three physical processes isassessed by computing their vertical and spectral variations for the subarctic winter and summer standardatmosphere using the radiation model MODTRAN3 (Moderate Resolution Transmittance code Version3). The results show that the process associated with the temperature contrast between the surface andthe atmosphere dominates over the other two processes ill magnitude. The magnitude of this process hassubstantial variations in the spectral region of 1250 to 1880 cm 1 and in the far infrared region. Due tothe low-level temperature inversion over the subarctic winter, there exists a negative contribution to thegreenhouse trapping. The seasonal variations are, however, dominated by the processes associated with theinteraction between the surface emissivity and the temperature contrast as well as the surface emissivityitself. The magnitudes of these two physical processes contributing to the greenhouse trapping over thesubarctic winter are about 7 to 10 times of those over the subarctic summer, whereas the magnitude ofthe processes associated with the temperature contrast ill the subarctic summer is only about 2 times ofthat in the subarctic winter.     

Property Regime or Development Policy? Explaining Growth in the U.S. Pacific Groundfish Fishery

Researchers often blame problems in fisheries on the property regime under which a fishery is practiced. Depending on their perspective, researchers locate the cause of problems in either common property or open access regimes. However, because these approaches rely on the assumption of the “economically rational individual,” they obfuscate the specific cultural, political, and economic practices that shape resource use. Analysis of the U.S. Pacific groundfish fishery shows that growth and subsequent problems in this fishery are the result of a state‐led fisheries development program implemented through a series of national, regional, and local policies designed to extend sovereign control to include ocean territory. These policies both created a climate of fisheries development and provided the means by which the fishery could grow. This analysis highlights the need to examine historic and geographic specificity to explain resource use, rather than relying upon generalized models that posit a deterministic relationship between property regimes and socioenvironmental outcomes.