The authors describe carbon system formulation and simulation characteristics of two new global coupled carbon–climate Earth System Models (ESM), ESM2M and ESM2G. These models demonstrate good climate fidelity as described in part I of this study while incorporating explicit and consistent carbon dynamics. The two models differ almost exclusively in the physical ocean component; ESM2M uses the Modular Ocean Model version 4.1 with vertical pressure layers, whereas ESM2G uses generalized ocean layer dynamics with a bulk mixed layer and interior isopycnal layers. On land, both ESMs include a revised land model to simulate competitive vegetation distributions and functioning, including carbon cycling among vegetation, soil, and atmosphere. In the ocean, both models include new biogeochemical algorithms including phytoplankton functional group dynamics with flexible stoichiometry. Preindustrial simulations are spun up to give stable, realistic carbon cycle means and variability. Significant differences...

GFDL’s ESM2 Global Coupled Climate–Carbon Earth System Models. Part I: Physical Formulation and Baseline Simulation Characteristics

Subfossil pollen and plant macrofossil data derived from 14 C-dated sediment profiles can provide quantitative information on glacial and interglacial cli- mates. The data allow climate variables related to growing- season warmth, winter cold, and plant-available moisture to be reconstructed. Continental-scale reconstructions have been made for the mid-Holocene (MH, around 6 ka) and Last Glacial Maximum (LGM, around 21 ka), allowing comparison with palaeoclimate simulations currently being carried out as part of the fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. The synthesis of the available MH and LGM climate recon- structions and their uncertainties, obtained using modern- analogue, regression and model-inversion techniques, is presented for four temperature variables and two moisture variables. Reconstructions of the same variables based on

/pdf/pollen-based-continental-climate-reconstructions-at-6-and-21-q7dw2mep3u.pdf

Pollen-based continental climate reconstructions at 6 and 21 ka: A global synthesis

Climate warming will adversely affect Canadian water quality and water quantity. The magnitude and timing of river flows and lake levels and water renewal times will change. In many regions, wetlands will disappear and water tables will decline. Habitats for cold stenothermic organisms will be reduced in small lakes. Warmer temperatures will affect fish migrations in some regions. Climate will interact with Overexploitation, dams and diversions, habitat destruction, non-native species, and pollution to destroy native freshwater fisheries. Acute water problems in the United States and other parts of the world will threaten Canadian water security. Aquatic communities will be restructured as the result of changes to competition, changing life cycles of many organisms, and the invasions of many non-native species. Decreased water renewal will increase eutrophication and enhance many biogeochemical processes. In poorly buffered lakes and streams, climate warming will exacerbate the effects of acid precipitation. Decreases in dissolved organic carbon caused by climate warming and acidification will cause increased penetration of ultraviolet radiation in freshwaters. Increasing industrial agriculture and human populations will require more sophisticated and costly water and sewage treatment.

The cumulative effects of climate warming and other human stresses on Canadian freshwaters in the new millennium

Canadian boreal woodlands and forests cover approximately 3.09 × 106 km2, located within a larger boreal zone characterized by cool summers and long cold winters. Warming since the 1850s, increases...

Anticipating the consequences of climate change for Canada’s boreal forest ecosystems1

This paper introduces a flexible sediment classification scheme for modern and ancient lake sediments employed at the Limnological Research Center, University of Minnesota. Our classification scheme emphasizes the macroscopic structure and microscopic components of the sedimentary matrix (clastic, chemical and biological) and can be applied to a wide range of lacustrine settings. Such a classification scheme is necessary to i) facilitate communication and collaboration between the highly interdisciplinary community of scientists that study lacustrine archives, ii) create a structure for comparative lacustrine sedimentological studies, and iii) take greater advantage of the great potential information recorded by changing depositional environments. Such a development is needed in light of current and planned Global Lake Drilling efforts and to expedite the creation of on-line, searchable databases of global lacustrine archives. A more comprehensive treatment of the topics discussed in this paper is available at: http: / / lrc.geo.umn.edu / services / handbook / sedclass.html.

Classification of lacustrine sediments based on sedimentary components

The climate of North America and the adjacent ocean at 6000 BP was estimated using five independent approaches. Using pollen data, the terrestrial climate was estimated by the movement of ecozone boundaries and by the method of modern analogues. Both analyses indicate warmer temperatures in the western Great Lakes area and the northern Great Plains. A model of Sphagnum-dominated peatland initiation, when forced by Canadian Climate Model 6 ka output projected a cooler and (or) wetter climate for continental western North America. Contrary to this, a reconstruction of the distribution of Sphagnum-dominated peatlands in western Canada indicates that they were located north of their modern distribution, suggesting warmer and (or) drier conditions at 6000 BP. This interpretation is strengthened by observations of lower lake levels at 6000 BP in western Canada. This drier climate may have been associated with warmer conditions as indicated by the quantitative climate reconstructions. In general, eastern North A...

/pdf/the-climate-of-north-america-and-adjacent-ocean-waters-ca-6-25qu3zedx6.pdf

The climate of North America and adjacent ocean waters ca. 6 ka

Sediments from three lakes in central Alberta, Smallboy Lake (53°35′N, 114°8′W), E.I. Pond (53°38′N, 112°51′W), and Hastings Lake (53°25′N, 112°53′W), have been analyzed for their pollen content, charcoal remains, and (in two lakes) pyrite spherule concentration. The earliest record (radiometrically dated at 7400 years BP) indicates the existence of mixed-wood parkland vegetation. By 5000 years BP the regional vegetation had a considerably more open structure than now and was subject to frequent fires, presumably a response to the warm, dry Hypsithermal climate of this time. The termination of the Hypsithermal Interval (4000 years bp) is recorded in all three lakes by a marked increase in precipitation. The onset of a cooler, moister climatic regime stimulated forest closure and reduced regional fire activity, although the local vegetation of each of the three study sites responded in a unique way to the changing climate. By 3000 years BP the vegetation resembled the modern vegetation. Little change is re...

A mid-Holocene record of vegetative change in central Alberta

Geomorphic systems of the Palliser Triangle, southern Canadian Prairies: description and response to changing climate

Clearwater Lake, Saskatchewan, is a relatively shallow, topographically closed, perennial lake cen trally located in the Palliser Triangle region of western Canada. Despite its present-day small size, Clearwater Lake is one of only a few lacustrine basins in this vast 400 000 km2 region of the northern Great Plains whose stratigraphic record extends to the early Holocene. Multiple proxy indicators are used to interpret the early-Holocene limnologic and hydrologic conditions in the basin. Changes in solute chemistry and concentration are reflected by siliceous microfossils and the endogenic and authigenic mineralogy of the sediment. The diatoms also provide evidence of fluctuations in water depth and water column stratification. Plant macrofossil assemblages, sediment texture and bedding features, and detrital mineralogy help to reconstruct drainage basin conditions and water level changes. Stable O-nd C-isotopic composition of inorganically precipitated, endo genic carbonate minerals provide insight into ...

/pdf/a-multi-proxy-limnologic-record-of-rapid-early-holocene-3ojfd0nz4x.pdf

A multi-proxy limnologic record of rapid early-Holocene hydrologic change on the northern Great Plains, southwestern Saskatchewan, Canada

Sediment lithology and mineralogy, as well as ostracode, plant macrofossil and stable isotope stratigraphies of lake sediment cores, are used to reconstruct late Holocene hydrologic changes at Kenosee Lake, a relatively large, hyposaline lake in southeastern Saskatchewan. Chronological control is provided by AMS radiocarbon ages of upland and shoreline plant macrofossils. All indicators outline an early, low-water, saline phase of lake history (4100–3000 BP), when the basin was occupied by a series of small, interconnected, sulfate-rich brine pools, as opposed to the single, topographically-closed lake that exists today. A rapid rise in lake-level (3000–2300 BP) led to the establishment of carbonate-rich, hyposaline lake conditions like those today. Lithostratigraphic data and ostracode assemblages indicate peak salinities were attained early in this period of lake infilling, suggesting that the lake-level rise was initially driven by an influx of saline groundwater. Lake-level and water chemistry have remained relatively stable over the last 2000 years, compared to earlier events. Because of a lack of datable organic material in sediments deposited during the last 2000 years, the chronology of recent events is not well resolved. Plant macrofossil, lithostratigraphic and ostracode evidence suggests that lake draw-down, accompanied by slightly higher than present salinites, occurred sometime prior to 600 BP, followed by peak lake-level and freshwater conditions. This most recent high lake stand, indicative of a high water table on the surrounding upland, may also have led to the establishment of an extensive cover of Betula in the watershed, possibly in response to paludification. Ostracode assemblages indicate that peak freshwater conditions occurred within the last 100 years. Since historically documented lake-level fluctuations correlate with decadal scale climatic fluctuations in the meteorological record, and late-Holocene hydrologic dynamics correspond to well documented climatic excursions of the Neoglacial and Little Ice Age, Kenosee Lake dynamics offer insight into the susceptibility of the region's water resources to climate change.

Hydrologic and climatic implications of a multidisciplinary study of late Holocene sediment from Kenosee Lake, southeastern Saskatchewan, Canada

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