Rapid Climate Changes and Extreme Weather Events on the Pacific Coast

Activity Rationale

This activity defines the nature and timing of past climate changes by interpreting the geologic record of north Pacific ocean and climate history contained in ocean sediment cores. This research provides key information on the causes, rates, critical thresholds, and past impacts of climate change on our environment. Defining past climate variability and understanding how our ocean-climate system works is essential to understand and accurately predict the nature of the abrupt climate changes we are now experiencing under global climate change.

Leader: Audrey Dallimore

The Topic

The water cycle describes the continuous transfer of water between the land, the atmosphere and the oceans.  It has many physical components that can be divided into two general categories: reservoirs and pathways.  Reservoirs are places where moisture is stored, such as glaciers, ice caps and sheets, permafrost, groundwater, lakes, rivers, wetlands, oceans, and the atmosphere.  Pathways are the mechanisms by which the moisture is transferred between these reservoirs.  They include precipitation, transpiration, evaporation, surface flows, and subsurface flows.  All of these components are strongly interconnected, such that when one is affected (e.g. by climate changes), the others are often affected as well.  Such changes can have substantial impacts on ecosystems, weather patterns, water quality and availability as well as power generation.

One important factor which is capable of influencing the water cycle on the Pacific coast, as well as across North America, is the Pacific Decadal Oscillation (PDO).  This is a pattern of climate variation which is characterized by 50-70 year cycles involving a positive and a negative phase, each of which lasts 20-30 years.  The positive phase is described as warm-dry weather, which is similar to, but not as pronounced as the effects of El Niño.   The negative phase is described as cool-wet weather conditions, similar to La Niña effects.  It is proposed that the unusual and somewhat extreme weather events on the West Coast since the year 2000 may be a result of a recent transition into the negative phase of the PDO, and may represent a “critical threshold” of a rapidly changing climate.

Scientists are able to identify the nature and timing of pre-historical climate variations by analyzing the composition of ocean sediment cores of annually laminated sediments from anoxic coastal inlets of British Columbia.  These sediments appear in the form of light and dark layers.  The light diatomaceous layers are a result of algal blooms during the warm summer months and are a “proxy” for the amount of sunshine and nutrients delivered to the coastal ocean in any given summer season. The dark terrigenous layers are related to the amount of precipitation that falls in a given year during the rainy winter months.  Therefore, the pattern of these layers in a sediment core indicates what the weather conditions were like in past years.  They can also indicate previous abrupt climate change events, possibly related to the PDO, that are similar to what we are experiencing now under global climate change.  This valuable knowledge can allow scientists to predict when such changes may occur again with our rapidly changing climate due to global climate change in the next century, and how long the effects may last.

Results

Historical analysis from our instrument record appears to reveal that the last climate “regime” shift occurred around 1976-1977.  From the mid-1940’s to the mid-1970’s, the climate on the West Coast was cooler and wetter, and from 1977 to 1997, the West Coast has enjoyed relatively warmer, drier weather.  However, scientists are now hypothesizing that there was another regime change around 1999 towards a period of cooler, variable weather. It is thought that the strong El Niño event of 1997-1998 followed by the moderate La Niña event of 1998-1999 may have catalyzed this regime shift (Dallimore et al., 2005).  If in fact such a regime shift has occurred, the West Coast will have to adapt and plan for cooler, stormier, more unstable weather for the next 20-30 years.

The relative positions and intensities of the north Pacific “weather-makers”, the atmospheric pressure systems called the  Aleutian Low in winter and the North Pacific High in summer, affect the position of the jet stream across North America as well as the amount and timing of precipitation all the way from the Pacific coast to central Canada.  Looking back in geologic time using laminated ocean sediments gives us an idea of the range of changes in these atmospheric systems and how these changes, in turn, affect ocean processes and ecosystems.  With this knowledge, we can understand the changing climate we are now experiencing and look forward to predict the range of changes we may reasonably expect in the future (as described in the report From Impacts to Adaptation: Canada in a Changing Climate 2007).

Potential impacts of Pacific ocean cycles (climate change) on some of the components of the water cycle

This research contributed to Canada’s National Scientific Assessment report of climate change in Canada: From Impacts to Adaptation: Canada in a Changing Climate 2007. With this report, it is now possible for Canadian communities to incorporate the best scientific knowledge of the expected impacts of global climate change into adaptation strategies that will increase the resilience of our communities to cope with the coming changes. In the report, scientists predict that for the west coast of Canada we can probably expect to experience the following changes:

Precipitation:

• Increases in the frequency and intensity of rainstorms are expected, as well as an increase in the frequency and intensity of sea surges and wind storms that could cause damages. One example that has already occurred was the sedimentation of Vancouver drinking water reservoirs during intense rainstorms of November, 2006.  This extreme rainstorm event and the resulting muddying of the Capilano reservoir resulted in the largest boil water advisory ever issued in Canada. Two million Vancouver area residents were without potable drinking water for ten days
• Storm events could affect infrastructure for storm water management.
• Changes in timing and amount of precipitation can also lead to drought and water shortages as was experienced in the B.C. coastal community of Tofino in the summer of 2006.
• Potential future decreases in precipitation could impact water management and storage planning.

Groundwater:

• Decreased quality due to increased mineral solubility and decreased dilution of contaminants in surface water bodies (turbidity).

Lakes and Reservoirs:

• Hydroelectric power generation challenges due to changes in the timing, intensity and magnitude of spring runoff.

Streams and runoff:

• Larger and/or more frequent severe floods causing increased expenditures.
• Increased erosion of banks.
• Decreased water quality due to increased contaminant concentrations (turbidity).

Links

NASA – The Water Cycle

An historical narrative on the Pacific Decadal Oscillation, inter-decadal climate variability and ecosystem impacts

Variations in the Pacific Decadal Oscillation over the past millennium

Where currents collide: In wild tides surging through the straits of Vancouver Island off British Columbia, marine life grows up strong and beautiful (National Geographic, August 2006)

Publications

Please note that subscriptions may be required to access some articles. To request a copy of publications, or for any more information, please contact Audrey Dallimore

• Check for more recent publications in GEOSCAN, the publications database of the Geological Survey of Canada and the Canada Centre for Remote Sensing.

Dallimore, A., Enkin, R.J., Baker, J. and Pienitz, R. 2009.  Stratigraphy and Late Holocene History of Effingham Inlet, B.C.: Results from MONA Core MD02-2494.  Geological Survey of Canada Open File 5930.

Dallimore, A., Enkin, R.J., Pienitz, R., Southon, J.R., Baker, J., Wright, C.A., Pedersen, T., Calvert, S.E., Ivanochko, T. and Thomson, R.E., 2008.  Postglacial evolution of a Pacific coastal fjord in British Columbia, Canada: interactions of sea-level change, crustal response, and environmental fluctuations – results from MONA core MD02-2494.  Canadian Journal of Earth Sciences 45: 1345- 1362.

Ivanochko, T.S., Calvert, S.E., Southon, J.R., Enkin, R.J., Baker, J., Dallimore, A., Pedersen, T.F., 2008.    Determining the post-glacial evolution of a northeast Pacific coastal fjord using a multiproxy geochemical approach.  Canadian Journal of Earth Sciences 45: 1-14.

Lemmen, D.S., Warren, F.J., Lacroix, J., and Bush, E. Editors, 2008.  From Impacts to Adaptation: Canada in a Changing Climate 2007; Government of Canada, Ottawa, Ontario, 448 p.

Hay, M.B., Dallimore, A., Thomson, R.E., Pienitz, R., and Calvert, S., 2007.  Siliceous microfossil record of late Holocene oceanography and climate along the west coast of Vancouver Island, British Columbia (Canada).  Quaternary Research 67: 33-49.

Wake, C.P., Dallimore, A., and Fisher, D.A., May 2006.  North Pacific Climate Workshop Final Report and Interactive Data Website. Please contact Audrey Dallimore for the password.

Columbia Basin Trust, 2007.  Climate Change in the Canadian Columbia Basin: Starting the Dialogue.

Dallimore, A., Thomson, R.E. and Bertram, M.A., 2005.  Modern to Late Holocene deposition in an anoxic fjord on the west coast of Canada: implications for regional oceanography, climate and paleoseismic history. Marine Geology 219: 47-69.