-
Coherence between lake ice cover, local climate and teleconnections (Lake Mendota, Wisconsin)
-
Ice duration has shortened and the ice-off date has become earlier for Lake Mendota from 1905 to 2000 as air temperatures have warmed and snowfall has increased. In addition, the ice record has cyclic compo- nents at inter-annual and inter-decadal scales. We examined the frequency domain relations between ice, local climate and the teleconnections, Southern Ocean Oscillation (SOI), Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), and Northern Pacific Index (NP), through a three-tiered analysis of coherence. The coherence results provide evidence of linear relations between the three levels at inter- annual and inter-decadal frequencies. Of the three local climate variables analyzed, namely temperature, snowfall and snow depth, temperature is the variable that most significantly affects ice duration and ice- off date, at both inter-annual and inter-decadal frequencies. The most significant effect of teleconnections on local climate are the effects of PDO on snowfall and snow depth, and SOI on temperature, at inter- annual frequencies, and the effect of NAO on snowfall at inter-decadal frequencies. The teleconnections that most significantly affect ice-cover duration and ice-off date, particularly at inter-decadal frequencies, are the PDO and the NAO. The influence of PDO on ice-cover appears to be transmitted through temper- ature, while the influence of the NAO appears to be transmitted through temperature and snowfall. A cas- cading set of links between teleconnections, local climate, and lake ice explain some, but not all, of the dynamics in these time series.
Lake ice, Local climate change, Teleconnections, Time series analysis,
Located in
Resources
/
Climate Science Documents
-
Potential climate warming effects on ice covers of small lakes in the contiguous U.S.
-
To simulate effects of projected climate change on ice covers of small lakes in the northern contiguous U.S., a process-based simulation model is applied. This winter icersnow cover model is associated with a deterministic, one-dimensional year-round water temperature model. The lake parameters required as model input are surface area, maximum depth, and Secchi depth as a measure of radiation attenuation. The model is driven by daily weather data. Weather records from 209 stations in the contiguous U.S. for the period 1961–1979 were used to represent past climate conditions. The projected climate changes due to a doubling of atmospheric CO2 were obtained from the output of the Canadian Climate Center Global Circulation Model. To illustrate the effect of projected climate change we present herein winter ice cover characteristics simulated, respectively, with inputs of past climate conditions Ž1961–1979., with inputs of a projected 2=CO2 climate scenario as well as differences of those values. The dependence of ice cover characteristics on latitude and lake characteristics has been quantified by making simulations for 27 lake types at 209 locations across the contiguous U.S. It was found that the 2=CO2 climate scenario is projected to delay ice formation on lakes by as much as 40 days and melt ice by up to 67 days earlier. Maximum ice thicknesses are projected to be reduced by up to 0.44 m ŽSault Ste. Marie, MI., and the ice cover periods will be shorter by up to 89 days ŽRock Springs, WY.. The largest changes are projected to occur east of Idaho from the Canadian border down to the states of Colorado, Nebraska, and Iowa and the northern parts of Illinois, Indiana, Ohio, and Pennsylvania. These changes would reduce fish winterkill in most shallow lakes of the northern states of the contiguous U.S. but may endanger snowmobiles and ice fishermen.
Keywords: climate change effect; ice cover; United States; lakes
Located in
Resources
/
Climate Science Documents
-
Temperature variations in lake ice in central Alaska, USA
-
In winter 2002/03 and 2003/04, thermistors were installed in the ice on two shallow ponds in central Alaska in order to obtain data on ice temperatures and their response to increasing and decreasing air temperatures, and flooding and snow-ice formation. Snow depth and density, and ice thickness were also measured in order to understand how they affected and were affected by ice temperature variability. The lowest ice temperature (–15.58C) and steepest temperature gradient (–39.88C m–1) occurred during a 9 week period in autumn when there was no snow on the ice. With snow on the ice, temperature gradients were more typically in the range –20 to –58C m–1. Average ice temperatures were lower during the warmer, first winter, and higher during the cooler, second winter because of differences in the depth and duration of the snow cover. Isothermal ice near the freezing point resulted from flooding and snow-ice formation, and brief episodes of warm weather with freezing rain. Under these circumstances, congelation-ice growth at the bottom of the ice cover was interrupted, even reversed. It is suggested that the patterns in temperatures brought about by the snow-ice formation and rain events may become more prevalent due to the increase in frequency of these events in central Alaska if temperature and precipitation change as predicted by Arctic climate models.
Located in
Resources
/
Climate Science Documents
-
Regional and Global Impacts of Land Cover Change and Sea Surface Temperature Anomalies
-
Model results show that, at the global scale, the physical impacts of LCC on temperature and rainfall are less important than large-scale SST anomalies, particularly those due to ENSO. However, in the regions where the land surface has been altered, the impact of LCC can be equally or more important than the SST forcing patterns in determining the seasonal cycle of the surface water and energy balance. Thus, this work provides a context for the impacts of LCC on climate: namely, strong regional-scale impacts that can sig- nificantly change globally averaged fields but that rarely propagate beyond the disturbed regions. This suggests that proper representation of land cover conditions is essential in the design of climate model experiments, particularly if results are to be used for regional-scale assessments of climate change impacts.
Located in
Resources
/
Climate Science Documents
-
Impacts of land use land cover on temperature trends over the continental United States
-
We investigate the sensitivity of surface temperature trends to land use land cover change (LULC) over the conterminous United States (CONUS) using the observation minus reanalysis (OMR) approach. We estimated the OMR trends for the 1979–2003 period from the US Historical Climate Network (USHCN), and the NCEP-NCAR North American Regional Reanalysis (NARR). We used a new mean square differences (MSDs)-based assessment for the comparisons between temperature anomalies from observations and interpolated reanalysis data. Trends of monthly mean temperature anomalies show a strong agreement, especially between adjusted USHCN and NARR (r = 0.9 on average) and demonstrate that NARR captures the climate variability at different time scales. OMR trend results suggest that, unlike findings from studies based on the global reanalysis (NCEP/NCAR reanalysis), NARR often has a larger warming trend than adjusted observations (on average, 0.28 and 0.27°C/decade respectively).
OMR trends were found to be sensitive to land cover types. We analysed decadal OMR trends as a function of land types using the Advanced Very High Resolution Radiometer (AVHRR) and new National Land Cover Database (NLCD) 1992–2001 Retrofit Land Cover Change. The magnitude of OMR trends obtained from the NLDC is larger than the one derived from the ‘static’ AVHRR. Moreover, land use conversion often results in more warming than cooling.
Overall, our results confirm the robustness of the OMR method for detecting non-climatic changes at the station level, evaluating the impacts of adjustments performed on raw observations, and most importantly, providing a quantitative estimate of additional warming trends associated with LULC changes at local and regional scales. As most of the warming trends that we identify can be explained on the basis of LULC changes, we suggest that in addition to considering the greenhouse gases–driven radiative forcings, multi-decadal and longer climate models simulations must further include LULC changes. Copyright 2009 Royal Meteorological Society
KEY WORDS land use land cover change; reanalysis; temperature trends; observed minus reanalysis approach; US historical climate network
Located in
Resources
/
Climate Science Documents
-
LAND USE PLANNING: A TIME-TESTED APPROACH FOR ADDRESSING CLIMATE CHANGE
-
Oregon’s land use planning program has protected an estimated 1.2 million acres of forest and agricultural land from development since its inception in 1973. As a result, these resource lands continue to provide forest products and food as well as another unexpected benefit: carbon storage. By keeping forests as forests, land use planning capitalizes on the natural landscape’s ability to sequester atmospheric carbon, a key contributor to climate change. Nationwide, however, forest land is the land type most frequently converted to more developed uses. When this happens, carbon storage opportunities are lost, and the new use, such as a housing development, often becomes a net carbon producer.
Scientists from the Pacific Northwest Research Station and Oregon Department of Forestry quantified the carbon storage maintained by the land use planning program in western Oregon. They found these gains were equivalent to avoiding 1.7 million metric tons of carbon dioxide emissions annually—the amount of carbon that would have been emitted by 395,000 cars in a year. Had the 1.7 million metric tons of stored carbon been released through development, Oregon’s annual increase in CO2 emissions between 1990 and 2000 would have been three times what it actually was. As policymakers look for ways to mitigate climate change, land use planning is a proven tool with measurable results.
Located in
Resources
/
Climate Science Documents
-
Effect of per-capita land use changes on Holocene forest clearance and CO2 emissions
-
The centerpiece of the early anthropogenic hypothesis is the claim that humans took control of greenhouse-gas trends thousands of years ago because of emissions from early agriculture (Ruddiman, 2003, 2007). A common reaction to this claim is that too few people lived thousands of years ago to have had a major effect on either land use or greenhouse-gas concentrations. Implicit in this view is the notion that per-capita land clearance has changed little for millennia, but numerous field studies have shown that early per-capita land use was large and then declined as increasing population density led to more intensive farming. Here we explore the potential impact of changing per-capita land use in recent millennia and conclude that greater clearance by early agriculturalists could have had a disproportionately large impact on CO2 emissions.
Located in
Resources
/
Climate Science Documents
-
The role of terrestrial plants in limiting atmospheric CO2 decline over the past 24 million years
-
Environmental conditions during the past 24 million years are thought to have been favourable for enhanced rates of atmospheric carbon dioxide drawdown by silicate chemical weathering1–7. Proxy records indicate, however, that the Earth’s atmospheric carbon dioxide concentrations did not fall below about 200–250 parts per million during this period8. The stabilization of atmospheric carbon dioxide concentrations near this minimum value suggests that strong negative feedback mechanisms inhibited further drawdown of atmospheric carbon dioxide by high rates of global silicate rock weathering. Here we investigate one possible negative feedback mechanism, occurring under relatively low carbon dioxide concentrations and in warm climates, that is related to terrestrial plant productivity and its role in the decomposition of silicate minerals9–11. We use simulations of terrestrial and geochemical carbon cycles and available experimental evidence to show that vegetation activity in upland regions of active orogens was severely limited by near-starvation of carbon dioxide in combination with global warmth over this period. These conditions diminished biotic-driven silicate rock weathering and thereby attenuated an important long-term carbon dioxide sink. Although our modelling results are semi-quantitative and do not capture the full range of biogeochemical feedbacks that could influence the climate, our analysis indicates that the dynamic equilibrium between plants, climate and the geosphere probably buffered the minimum atmospheric carbon dioxide concentrations over the past 24 million years.
Located in
Resources
/
Climate Science Documents
-
The emergence of land change science for global environmental change and sustainability
-
Land change science has emerged as a fundamental component of global environmental change and sustainability research. This interdisciplinary field seeks to understand the dynamics of land cover and land use as a coupled human–environment system to ad- dress theory, concepts, models, and applications relevant to environmental and societal problems, including the intersection of the two. The major components and advances in land change are addressed: observation and monitoring; understanding the coupled system—causes, impacts, and consequences; modeling; and synthesis issues. The six articles of the special feature are introduced and situated within these components of study.
Located in
Resources
/
Climate Science Documents
-
Impact of deforestation in the Amazon basin on cloud climatology
-
Shallow clouds are prone to appear over deforested surfaces whereas deep clouds, much less frequent than shallow clouds, favor forested surfaces. Simultaneous atmospheric soundings at forest and pasture sites during the Rondonian Boundary Layer Experiment (RBLE-3) elucidate the physical mechanisms responsible for the observed correlation between clouds and land cover. We demonstrate that the atmospheric boundary layer over the forested areas is more unstable and characterized by larger values of the convective available potential energy (CAPE) due to greater humidity than that which is found over the deforested area. The shallow convection over the deforested areas is relatively more active than the deep convection over the forested areas. This greater activity results from a stronger lifting mechanism caused by mesoscale circulations driven by deforestation-induced heterogeneities in land cover.
climate land-cover heterogeneity mesoscale circulations
Located in
Resources
/
Climate Science Documents
