Paleolimnological Perspectives on Directional …Paleolimnological Perspectives on Directional Environmental Change in the PAD John P. Smol, OC, PhD, FRSC Professor and Canada Research

Paleolimnological Perspectives on Directional Environmental

Change in the PAD

John P. Smol, OC, PhD, FRSC Professor and Canada Research Chair in Environmental Change

Paleoecological Environmental Assessment and Research Laboratory (PEARL)

Dept. Biology, Queen’s University

Important management questions

What were pre-disturbance conditions? (what is natural?) What is the range of natural variability? Have conditions changed? How? How much? When? Why?

Techniques to Assess Environmental Change

historical records and traditional knowledge

modeling

natural archives

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Information from outside the lake

Information from within the lake

Paleolimnology: Tracking long-term ecosystem changes using information preserved in lake and river sediments

Sediment Coring

Close-Interval Sectioning

2 4

6 8

10 12

14 16

18 20

22 24

26 28

30 32

34 36

-5

0 5 10

15

20

25

30

35

40

45

50

214Bi

137Cs

210Pb

Cor

e D

epth

(cm

)

0

Dating the sedimentary sequences

• 210Pb & 137Cs (radioisotopes)

2002 2001 1999 1998 1996 1994 1992 1990 1987 1985 1981 1976 1972 1965 1950 1946 1936 1926 1920

1900 1890 1870 1860 1856 1850 1846

1910

2003 2004 2005 2006 Youngest

Oldest

Con

tinuo

us R

ecor

d

Activity (dpm/g)

~1963

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Freshwater diatoms: Microscopic plant-like organisms

Photos: K. Laird and B. Cumming; Fig. 5.4 in Smol (2008)

Select Study Lake

Collect Indicator Data

Sub-sample Sediments & Isolate Indicator of Interest

Analyze Data

Section & Date Sediment Core Select Coring Site & Retrieve Sediment Core

The Paleolimnological Approach

Photos courtesy of B. Cumming, I. Walker, Dell & Lei

210Pb 137Cs 14C

There are many more examples of directional environmental change described using

paleolimnological techniques

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Standardization of Methods

e.g., Developments in Paleoenvironmental Research book series 11

~700 page book on using diatoms as indicators!

These approaches are used around the world.

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Is there paleolimnological evidence for post-1968

directional environmental change in the PAD?

Similar approaches were used in the PAD project to answer the question:

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Peace-Athabasca Delta

desiccation flooded trees

high water marks

dead willow fringe 14

Research Questions

• What is the range of natural variability of hydrological and ecological conditions in the delta, how is that related to climatic variability, flood frequency and geomorphic change? • Does natural variability include multi-decadal periods without major flooding and low lake levels? • Are the hydro-ecological conditions during the post-regulation period (since 1968) outside the range of natural variation?

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Open drainage = connection to river

Closed or Restricted drainage = occasional or no connection to river

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Diatom Assemblages: Open-Drainage Lakes Fragilaria pinnata

Cyclostephanos PAD sp. 1

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Diatom Assemblages: Closed/Restricted-Drainage Lakes

Navicula minima Cocconeis placentula

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Stable isotopes (e.g. 18O /16O)

http://serc.carleton.edu/microbelife/research_methods/environ_sampling/stableisotopes.html

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20

21

22

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Four Examples Demonstrating Approach

1) PAD 9 - comparing changes using paleolimnology and comparison to historic maps

2) North Pond – a 5,200 year perspective on Lake Athabasca water levels.

3) Oxbow lakes – paleo-flood frequency

4) Athabasca Cutoff - Can paleolimnology track known drying (and wetting) due to known engineered and natural changes?

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Central location in PAD, willow evidence of water level changes

25 Sinnatamby et al., 2010, JOPL

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27

Sinnatamby et al., 2010, JOPL

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Sinnatamby et al., 2010, JOPL

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Sinnatamby et al., 2010, JOPL

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Lots of flooding

High flow

Low flooding

Sinnatamby et al., 2010, JOPL

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Can take longer cores to track changes over millennia

32 North Pond – paleo-water level recorder

~5,200 Year Perspective on Water Levels in Lake Athabasca

(Wolfe et al., 2011, GRL) 33

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Hydrol. Earth Syst. Sci., 17, 1681–1691, 2013 Streamflow input to Lake Athabasca, Canada K. Rasouli, M. A. Hern´andez-Henr´ıquez, and S. J. D´ery

“Results show that the Athabasca River, which is the main contributor to the total lake inflow, experienced marked declines in recent decades impacting lake levels and its ecosystem. From 1960 to 2010 there was a significant reduction in lake inflow and a significant recession in the Lake Athabasca level. Our trend analysis corroborates a previous study using proxy data obtained from nearby sediment cores suggesting that the lake level may drop 2 to 3m by 2100.”

(From abstract)

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Oxbow lakes – PAD 54 and 15

Past-Flood Recorders

PAD 54 Sediment Core

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From Wolfe et al. (2006)

Magnetic Susceptibility

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Flood

Flood

Magnetic susceptibility-inferred flood frequency and magnitude Wolfe et al. (2006)

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Comparison to Historical Flood Record

magnetic susceptibility (κ)

0 200 400 6000 200 400 600

year

AD

1700

1725

1750

1775

1800

1825

1850

1875

1900

1925

1950

1975

2000

PAD 54 PAD 15

floods/year

0.0 0.2 0.4 0.6 0.8 1.0

year

AD

1700

1725

1750

1775

1800

1825

1850

1875

1900

1925

1950

1975

2000

Peace R. spring ice jamfloods/year

(Timoney et al. 1997)

• Lake sediment flood frequency records closely correspond with the historical flood record for the Peace River

[Wolfe et al. 2006 Hydrological Processes]

1) Low flood frequency during 1700s 2) Intervals of high flood frequency from ~1785 to ~1815 3) Decline in flood frequency starting ~1900 4) Several intervals without major floods during past 300 years

Conclusions for PAD 15 (Wolfe et al. 2006)

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Can the paleolimnologists track known events which caused decreased and increased water levels?

How Sensitive are these Techniques?

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Wolfe et al., 2008, Ecohydrology

43 Wolfe et al., 2008, Ecohydrology

Post-1972 drying

Many lakes were studied over 12 years – all published in the peer-reviewed literature, providing a consistent story.

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Smol & Douglas (2007) PNAS 104: 12395-7. 46

Many shallow lake systems have been drying out over the same time period, clearly unrelated to regulation.

High Arctic Ponds – Ellesmere Island

Is there paleolimnological evidence for post-1968 directional

environmental change in the PAD?

Based on a weight-of-evidence approach, the profiles do not record any consistent changes coincident with the period of river flow regulation.

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The paleolimnological data indicate that changes that occurred in deeper (older) sections of the cores were as great or much greater than any changes noted in the most recent sediments.

The direction and magnitude of changes recorded in the recent sediments of the cores are not consistent with a drying trend coincident with river flow regulation.

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Are the PAD paleolimnological data credible?

1) State-of-the-art paleolimnological approaches were used.

2) It was a multi-proxy study, with internal checks on interpretations.

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Are the PAD paleolimnological data credible?

3) Importantly, all this work has passed rigorous peer-review in international journals.

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My conclusions concerning the paleolimnological the PAD data

1) No one ever said delta ecosystems were simple!

2) The paleolimnological data clearly record a large number of interesting environmental changes in the histories of these highly dynamic systems.

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3) Using a weight-of-evidence approach, I cannot identify any discernible signal related to river flow regulation.

(I fully expected to see one when this project started)

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Impacts of Regulation on the PAD

Dr. Kevin Timoney Ph.D.

• The period 1960-67 was wetter and more flood-prone than some other documented periods such as the 1890s and the 1940s. Although it is common to focus on the 1960-67 period due to the availability of the Peace Point discharge data, that period is not characteristic of the longer-term record.

• Woody vegetation communities have been increasing delta-wide for decades. There is no evidence regulation has played a factor.

Impacts of Regulation on the PAD

Dr. Kevin Timoney Ph.D.

• Both the ecosystem and navigation have been

impacted by human activities (prevention of the Athabasca River mainstem avulsion, cessation of dredging, weirs) and natural geomorphic changes (Cree Creek avulsion, Cree Creek and Athabasca Delta progradation).

• The delta is undergoing a long-term drying trend whose onset precedes Peace River regulation by many decades.

From Timoney, K.P. 2013. The Peace-Athabasca Delta: Portrait of a Dynamic Ecosystem

Dry Mamawi Lake 1950 Wet Mamawi Lake 2001

Impacts of Regulation on Ice Jams

Dr. Derald Smith Ph.D.

• There has been little change in frequency of ice-

jam floods on the Peace River in the PAD since construction of the W.A.C. Bennett Dam.

• Moreover, there is little to no difference in flood frequency from the flood-bed and tree-scar records between the Peace and Athabasca rivers, though both rivers originate from similar geomorphic and climatic watersheds.

PAD Hydraulics and Hydrology

Dr. Stephen Burges Ph.D., P.E. (Wash.), P.H. (AIH), D.WRE (AAWRE)

• Hydrologic recharge depends on location in the delta, local precipitation and runoff, Peace River flow above Hudson’s Hope and tributary inflows, Athabasca Rive flows, the weirs, wind set-up, and the inter-relationship of the lakes, and ice jams and Peace River flow reversals.

PAD Hydraulics and Hydrology

Dr. Stephen Burges Ph.D., P.E. (Wash.), P.H. (AIH), D.WRE (AAWRE)

• Natural geomorphic (Cree Creek) changes have had major impacts on local recharge and delta transportation.

• Delta annual maximum lake levels do not differ post-dam vs. the entirety of the pre-dam record.

Impacts of Regulation on Ice Jams

Dr. George Ashton Ph.D.

• Freeze-up flows from Bennett Dam have increased

the discharge required to initiate breakup.

• However, the higher flows and the storage release due to the deeper flows (higher stage) equal or exceed the needed increase. Thus, breakup flows that result in flooding of the PAD are largely dependent upon contributions of runoff from downstream of Bennett Dam.