An introduction to the Dorset special issue: transforming understanding of factors that regulate aquatic ecosystems on the southern Canadian Shield

2008 ◽  
Vol 65 (5) ◽  
pp. 781-785 ◽  
Author(s):  
Norman D Yan ◽  
Andrew M Paterson ◽  
Keith M Somers ◽  
Wolfgang A Scheider
Keyword(s):  
El Niño ◽  
Aquatic Ecosystems ◽  
Environmental Science ◽  
Multiple Stressors ◽  
El Nino ◽  
Canadian Shield ◽  
Interactive Effects ◽  
Special Issue ◽  
Management Interventions ◽  
South Central

This special issue demonstrates that aquatic ecosystems on the south-central Canadian Shield have changed in many ways over the last three decades. El Niño cycles have synchronized multilake dynamics in lake-water chemistry and in several components of the aquatic biota. Overlain on this cyclic regional pattern, phosphorus, sulphate, and calcium levels have all declined, whereas alkalinity has not yet risen in the most acid-sensitive study lakes, despite large reductions in SO2 emissions. Further, novel and unanticipated stressors have appeared, including nonindigenous predator introductions, Ca decline, salinity increase, and autumn spikes in metals following El Niño induced droughts. The resident biota are clearly responding not only to the familiar historical phosphorus and acid stressors, but also to the interactive effects of changes in multiple stressors in a warming environment. Lakes are best managed with an understanding of dominant limnological trends, their causes, and their responses to past management interventions. The research conducted at the Dorset Environmental Science Centre indicates “progress but no cigar” on acid rain, proof of climate variability as a direct and indirect regulator of south-central Shield ecosystems, and the emergence of novel stressors, the effects of which we cannot yet fully predict.

scholarly journals Response of the Antarctic stratosphere to warm pool El Niño Events in the GEOS CCM

2011 ◽  
Vol 11 (3) ◽  
pp. 9743-9767 ◽  
Author(s):  
M. M. Hurwitz ◽  
I.-S. Song ◽  
L. D. Oman ◽  
P. A. Newman ◽  
A. M. Molod ◽  
...  
Keyword(s):  
El Niño ◽  
Planetary Wave ◽  
Lower Stratosphere ◽  
El Nino ◽  
Warm Pool ◽  
Wave Activity ◽  
Central Pacific ◽  
Quasi Biennial Oscillation ◽  
South Central ◽  
The Antarctic

Abstract. A new formulation of the Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM), with an improved general circulation model and an internally generated quasi-biennial oscillation (QBO), is used to investigate the response of the Antarctic stratosphere to (1) warm pool El Niño (WPEN) events and (2) the sensitivity of this response to the phase of the QBO. Two 50-yr time-slice simulations are forced by repeating annual cycles of sea surface temperatures and sea ice concentrations composited from observed WPEN and neutral ENSO (ENSON) events. In these simulations, greenhouse gas and ozone-depleting substance concentrations represent the present-day climate. The modelled responses to WPEN, and to the phase of the QBO during WPEN, are compared with NASA's Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis. WPEN events enhance poleward planetary wave activity in the central South Pacific during austral spring, leading to relative warming of the Antarctic lower stratosphere in November/December. During the easterly phase of the QBO (QBO-E), the GEOS V2 CCM reproduces the observed 3–5 K warming of the polar region at 50 hPa, in the WPEN simulation relative to ENSON. In the recent past, the response to WPEN events was sensitive to the phase of the QBO: the enhancement in planetary wave driving and the lower stratospheric warming signal were mainly associated with WPEN events coincident with QBO-E. In the GEOS V2 CCM, however, the Antarctic response to WPEN events is insensitive to the phase of the QBO: the modelled response is always easterly QBO-like. OLR, streamfunction and Rossby wave energy diagnostics are used to show that the modelled QBO does not extend far enough into the lower stratosphere and upper troposphere to modulate convection and thus planetary wave activity in the south central Pacific.

Response of benthic macroinvertebrate communities to El Niño related drought events in six upland streams in south-central Ontario

2008 ◽  
Vol 65 (5) ◽  
pp. 890-905 ◽  
Author(s):  
Beth Gilbert ◽  
Peter J Dillon ◽  
Keith M Somers ◽  
Ron A Reid ◽  
Lem Scott
Keyword(s):  
Relative Abundance ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Benthic Macroinvertebrate ◽  
Macroinvertebrate Communities ◽  
South Central ◽  
Effects Of Drought ◽  
One Year ◽  
The Impact

We examined the effects of extreme drought events on benthic macroinvertebrate (BMI) community structure in six forested upland streams in south-central Ontario, Canada, during a 9-year period. Variation in the mean winter El Niño – Southern Oscillation Index was strongly correlated with drought conditions (zero flow days) in the study streams. Drought onset and duration varied among study streams and among years. Below-average precipitation coincided with the occurrence of drought, although it remains unclear if snowfall and rainfall contributed equally to the impact of decreased precipitation. Increased relative abundance of Ephemeroptera, Plecoptera, and Trichoptera (EPT) one year following drought and decreased relative abundance two years after drought indicated high resistance but poor resilience. In contrast, chironomids showed poor resistance and high resilience. Although these patterns were not consistent across all streams, temporal coherence among streams was found in percent EPT, percent chironomids, and percent dipterans, suggesting that drought acts as a disturbance mechanism that simplifies benthos community assemblages. Biocriteria developed from 22 nearby reference streams indicated that abnormal BMI communities occurred only after recurring episodes of drought, indicating that the effects of drought are cumulative. Headwater streams may prove to be sentinel ecosystems for monitoring the impacts of climate change.

scholarly journals A review of the effects of Bythotrephes longimanus and calcium decline on zooplankton communities — can interactive effects be predicted?

2015 ◽  
Vol 23 (4) ◽  
pp. 395-413 ◽  
Author(s):  
Shakira S.E. Azan ◽  
Shelley E. Arnott ◽  
Norman D. Yan
Keyword(s):  
Multiple Stressors ◽  
Current Knowledge ◽  
Canadian Shield ◽  
Interactive Effects ◽  
Bythotrephes Longimanus ◽  
Negative Impacts ◽  
The Individual ◽  
Zooplankton Communities ◽  
Shield Lakes ◽  
Review Current

Anthropogenic stressors including acid deposition, invasive species, and calcium (Ca) decline have produced widespread damage to Canadian Shield lakes, especially to their zooplankton communities. Here, we review current knowledge on the individual effects on zooplankton by the non-indigenous predator Bythotrephes longimanus and Ca decline; we identify knowledge gaps in this literature and examine the likely interactive impacts of Bythotrephes invasions and Ca decline on zooplankton. The negative impacts of Bythotrephes longimanus on zooplankton communities are well known, whereas current understanding of the effects of declining Ca on zooplankton is restricted to Daphnia spp.; hence, there is a large knowledge gap on how declining Ca may affect zooplankton communities in general. The co-occurring impacts of Bythotrephes and declining Ca have rarely been studied at the species level, and we expect daphniids, particularly Daphnia retrocurva and Daphnia pulicaria, to be the most sensitive to both stressors. We also expect a synergistic negative interaction on cladocerans in lakes with both stressors, leaving a community dominated by Holopedium glacialis and (or) copepods. Our predictions form testable hypotheses but since species and ecosystem response to multiple stressors are difficult to predict, we may actually see ecological surprises in Canadian Shield lakes as Bythotrephes continues to spread and Ca levels continue to fall.

scholarly journals Fire, drought and El Niño relationships on Borneo during the pre-MODIS era (1980–2000)

2011 ◽  
Vol 8 (1) ◽  
pp. 975-1013 ◽  
Author(s):  
M. J. Wooster ◽  
G. L. W. Perry ◽  
A. Zoumas
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Large Fire ◽  
Active Fire ◽  
South Central ◽  
Rainfall Deficit ◽  
Fire Activity

Abstract. Borneo (Indonesia) is Earth's third largest island, and the location of both extensive areas of rainforest and tropical peatlands. It is the site of both regular (seasonal) biomass burning associated with forest clearance and agricultural production preparations, and occasional, but much more severe, large fire episodes releasing enormous volumes of carbon from burning vegetation and peat. The latter's extreme magnitude is believed to be associated with the severity of El Niño related droughts. Over the last decade, data from the EOS MODIS satellite instruments have been used to study fire on Borneo, but earlier large fire events remain less well documented. Here we focus on the study of Borneo's large fire episodes in the "pre-MODIS" era, and specifically a 20 year period covering both the two strongest El Niño-Southern Oscillation (ENSO) events on record (1997–1998 and 1982–1983) and an unprecedented series of more frequent, but weaker, El Niño's. For the five El Niño episodes occurring between 1980 and 2000, we develop quantitative measures of Borneo's fire activity based on active fire counts derived from NOAA AVHRR Global Area Coverage (CAC) satellite data. We use these metrics to investigate relationships between the strength and timing of the El Niño-Southern Oscillation (ENSO) event, the associated drought, and the fire activity magnitude. Significant fires are identified across parts of South, Central, East and West Kalimantan, always occurring within two or three fire sub-seasons separated by monsoons. We find that the length, overall strength, and growth rate of individual El Niño episodes effects the extent and harshness of the drought, and the magnitude of fire activity. We confirm significant correlations between monthly ENSO index and rainfall deficit measures, and between rainfall deficit and fire. The two strongest El Niño episodes are accompanied by the most abundant fires, showing two and three times the active fire count seen in the next largest fire year. The most significant statistical association found between ENSO strength and fire activity is that between the 16-month sum of the Niño-3 anomaly and the simultaneously recorded number of active fire counts (r2

scholarly journals Response of the Antarctic stratosphere to warm pool El Niño Events in the GEOS CCM

2011 ◽  
Vol 11 (18) ◽  
pp. 9659-9669 ◽  
Author(s):  
M. M. Hurwitz ◽  
I.-S. Song ◽  
L. D. Oman ◽  
P. A. Newman ◽  
A. M. Molod ◽  
...  
Keyword(s):  
El Niño ◽  
Planetary Wave ◽  
Lower Stratosphere ◽  
El Nino ◽  
Warm Pool ◽  
Wave Activity ◽  
Central Pacific ◽  
Quasi Biennial Oscillation ◽  
South Central ◽  
The Antarctic

Abstract. The Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM) is used to investigate the response of the Antarctic stratosphere to (1) warm pool El Niño (WPEN) events and (2) the sensitivity of this response to the phase of the QBO. A new formulation of the GEOS V2 CCM includes an improved general circulation model and an internally generated quasi-biennial oscillation (QBO). Two 50-yr time-slice simulations are forced by repeating annual cycles of sea surface temperatures and sea ice concentrations composited from observed WPEN and neutral ENSO (ENSON) events. In these simulations, greenhouse gas and ozone-depleting substance concentrations represent the present-day climate. The modelled responses to WPEN, and to the phase of the QBO during WPEN, are compared with NASA's Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis. WPEN events enhance poleward tropospheric planetary wave activity in the central South Pacific region during austral spring, leading to relative warming of the Antarctic lower stratosphere in November/December. During the easterly phase of the QBO (QBO-E), the GEOS V2 CCM reproduces the observed 4–5 K warming of the polar region at 50 hPa, in the WPEN simulation relative to ENSON. In the recent past, the response to WPEN events was sensitive to the phase of the QBO: the enhancement in planetary wave driving and the lower stratospheric warming signal were mainly associated with WPEN events coincident with QBO-E. In the GEOS V2 CCM, however, the Antarctic response to WPEN events is insensitive to the phase of the QBO: the modelled response is always easterly QBO-like. The QBO signal does not extend far enough into the lower stratosphere and upper troposphere to modulate convection and thus planetary wave activity in the south central Pacific.

scholarly journals ENSO and IOD teleconnections for African ecosystems: evidence of destructive interference between climate oscillations

2011 ◽  
Vol 8 (1) ◽  
pp. 27-40 ◽  
Author(s):  
C. A. Williams ◽  
N. P. Hanan
Keyword(s):  
El Niño ◽  
Land Surface ◽  
Vegetation Change ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Interactive Effects ◽  
Surface Model ◽  
Destructive Interference ◽  
Climate Oscillations

Abstract. Rainfall and vegetation across Africa are known to resonate with the coupled ocean-atmosphere phenomena of El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). However, the regional-scale implications of sea surface temperature variability for Africa's photosyntheis have received little focused attention, particularly in the case of IOD. Furthermore, studies exploring the interactive effects of ENSO and IOD when coincident are lacking. This analysis uses remotely sensed vegetation change plus a land surface model driven with observed meteorology to investigate how rainfall, vegetation, and photosynthesis across Africa respond to these climate oscillations. In addition to the relatively well-known ENSO forcing, the IOD induces large departures of photosynthesis across much of Africa associated with anomalies in rainfall and vegetation greenness. More importantly, sizeable independent effects can be suppressed or even reversed by destructive interferences during periods of simultaneous ENSO and IOD activity. For example, effects of positive IOD on southeastern Africa tended to dominate those of El Niño during their coincidence spanning 1997–1998, with sign reversal of El Niño's typically strong suppression of photosynthesis in this region. These findings call into question past analyses examining teleconnections to ENSO or IOD in isolation, and indicate the need to consider their simultaneous states when examining influences on hydroclimatic and ecological conditions across Africa.

El Niño Flavors and Their Simulated Impacts on Atmospheric Circulation in the High Southern Latitudes*

2014 ◽  
Vol 27 (23) ◽  
pp. 8934-8955 ◽  
Author(s):  
Aaron B. Wilson ◽  
David H. Bromwich ◽  
Keith M. Hines ◽  
Sheng-hung Wang
Keyword(s):  
Atmospheric Circulation ◽  
High Latitude ◽  
El Niño ◽  
El Nino ◽  
South Pacific ◽  
Tropical Pacific ◽  
The South ◽  
Wave Source ◽  
South Central ◽  
El Niño Flavors

Abstract Two El Niño flavors have been defined based on whether warm sea surface temperature (SST) anomalies are located in the central or eastern tropical Pacific (CP or EP). This study further characterizes the impacts on atmospheric circulation in the high latitudes of the Southern Hemisphere associated with these types of El Niño events though a series of numerical simulations using the National Center for Atmospheric Research Community Atmosphere Model (CAM). Comparing results with the Interim ECMWF Re-Analysis (ERA-Interim), CAM simulates well the known changes to blocking over Australia and a southward shift in the subtropical jet stream across the eastern Pacific basin during CP events. More importantly for the high southern latitudes, CAM simulates a westward shift in upper-level divergence in the tropical Pacific, which causes the Pacific–South American stationary wave pattern to shift toward the west across the entire South Pacific. These changes to the Rossby wave source region impact the South Pacific convergence zone and jet streams and weaken the high-latitude blocking that is typically present in the Amundsen-Bellingshausen Seas during EP events. Anticyclonic flow becomes established farther west in the south central Pacific, modifying high-latitude heat and momentum fluxes across the South Pacific and South Atlantic associated with the ENSO–Antarctic dipole.

scholarly journals ENSO and IOD teleconnections for African ecosystems: evidence of destructive interference between climate oscillations

2010 ◽  
Vol 7 (4) ◽  
pp. 6323-6352
Author(s):  
C. A. Williams ◽  
N. P. Hanan
Keyword(s):  
El Niño ◽  
Land Surface ◽  
Vegetation Change ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Interactive Effects ◽  
Surface Model ◽  
Destructive Interference ◽  
Climate Oscillations

Abstract. Rainfall and vegetation across Africa are known to resonate with the coupled ocean-atmosphere phenomena of El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). However, the regional-scale implications of sea surface temperature variability for Africa's carbon sources and sinks have received little focused attention, particularly in the case of IOD. Furthermore, studies exploring the interactive effects of ENSO and IOD when coincident are lacking. This analysis uses remotely sensed vegetation change plus a land surface model driven with observed meteorology to investigate how rainfall, vegetation, and photosynthesis across Africa respond to these climate oscillations. In addition to the relatively well-known ENSO forcing, the IOD induces large departures of photosynthesis across much of Africa associated with anomalies in rainfall and vegetation greenness. More importantly, sizeable independent effects can be suppressed or even reversed by destructive interferences during periods of simultaneous ENSO and IOD activity. For example, effects of positive IOD on southeastern Africa tended to dominate those of El Niño during their coincidence spanning 1997–1998, with sign reversal of El Niño's typically strong suppression of photosynthesis in this region. These findings call into question past analyses examining teleconnections to ENSO or IOD in isolation, and indicate the need to consider their simultaneous states when examining influences on hydroclimatic and ecological conditions across Africa.

scholarly journals Doliolid (Tunicata, Thaliacea) Blooms in the Southeastern Gulf of Alaska as a Result of the Recent Marine Heat Wave of 2014–2016

2021 ◽  
Vol 8 ◽  
Author(s):  
Alexei I. Pinchuk ◽  
Sonia D. Batten ◽  
Wesley W. Strasburger
Keyword(s):  
Heat Wave ◽  
El Niño ◽  
El Nino ◽  
Mesoscale Eddy ◽  
Gulf Of Alaska ◽  
Eastern Coast ◽  
Spatial And Temporal Variability ◽  
The South ◽  
Sea Temperature ◽  
South Central

The eastern North Pacific experienced a prolonged heat wave in 2014–2016 manifested by high sea surface temperature anomalies in the south-central Gulf of Alaska (GOA). The event provided a natural experiment on the response of the southern GOA ecosystem to a dramatic change in sea temperature. Spatial and temporal variability in zooplankton communities following the culmination of the heat wave was investigated as a part of the NOAA Eastern GOA Ecosystem Assessment program in 2016–2017. Here, for the first time in the GOA, we report consistent observations of doliolid (Dolioletta tritonis) swarms observed in the upper mixed layer beyond the shelf break during both years, with the maximal density of 3,847 ind m–3 recorded in August 2016 and coinciding with the location of an offshore cyclonic mesoscale eddy. Doliolid density was significantly lower on the shelf. The long-term Continuous Plankton Recorder (CPR) data indicated that doliolid blooms in the south-central GOA may have occurred in the past two decades during El-Nino events. Coincidentally, doliolids prevailed in the diets of juvenile sablefish collected along the eastern coast of GOA both during the 2014–2016 heat wave and during 1997–1998 El Nino. Thus, we speculate that warming trends may increase the importance of doliolids in the GOA pelagic food web.

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