Effects of Climate Changeon the Great LakesELIORA BUJARIMay 5, 2009

Objective

Look at streamflow, precipitation, and temperature measurements over the past fifty eight years to study any statistical trends that indicate the effects of climate change on the Great Lakes.

Use these trends to evaluate future predictions.

Location of the Lakes Contain about 6 quadrillion gallons of water, and

combined the lakes provide approximately 18% of the world’s freshwater supply.

Statistical Analysis

Mann-Kendall Analysis

Non-parametric method used in hydrologic data analysis to detect trends, using the S and Zs statistic.

Null hypothesis : there is no monotonic trend in the data.

Simple Linear Regression Analysis

Y = m x + b and R2 statistics Used to test the slopes of the trend lines and estimate future values.

Lake Levels At a 95% confidence interval the tests showed an increasing trend for the lake levels, except for Lake Superior

Mann-Kendall: S-score = 1819 Zs = 6.34 Result = Increasing Trend

Simple Linear Regression:

Water Level = 158.32 + 0.0081*Year

(77.92) (7.78)

R2 = 0.408 Se = 0.256 F = 60.58

1900 1920 1940 1960 1980 2000 2020173.2

173.4

173.6

173.8

174.0

174.2

174.4

174.6

174.8

175.0

175.2

Lake Erie Levels

95% CIRegression Line

Leve

l (m

)

Lake Levels

1900 1920 1940 1960 1980 2000 2020-1.00

-0.80

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

Lake Erie

Lake Michigan

Lake Superior

Lake Huron

Lake Ontario

Diff

eren

ce in

leve

ls fr

om th

e m

ean

(m)

Temperature Trends No statistically significant trends on overlake temperatures for Lake Erie, Huron, and Ontario, but there is an increasing trend for Lake Michigan and Lake Superior.

Mann-Kendall: S-score = 135 Zs = 0.92 Result = No Trend

Simple Linear Regression:

Temperature = -6.806 + 0.009*Year

(-0.569) (1.54)

R2 = 0.039 Se = 0.743 F = 2.17

1940 1950 1960 1970 1980 1990 2000 20100

2

4

6

8

10

12

14

16Lake Erie Temperature: 1948-2005

95% CI

Tem

pera

ture

(0C)

Flow Trends

There are no Statistically Significant Trends for streamflow

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 20100

750

1500

2250

3000

3750

4500

5250

6000

6750

7500

8250

9000Average Annual Streamflow from 1948-2005

Detroit RiverLinear (Detroit River)St Mary's River

Flow

(m3/

sec)

Precipitation Trends

Statistically Significant Increasing Trends for Lake Huron and Lake Ontario.

Mann-Kendall: S-score = 423 Zs = 2.83 Result = Increasing

Trend

Simple Linear Regression:

Precipitation = -224.4 + 0.150*Year

(2.269) (3.00)

R2 = 0.138 Se = 6.380 F = 8.975

1940 1950 1960 1970 1980 1990 2000 20100

10

20

30

40

50

60

70

80

90Precipitation over Lake Huron: 1948-2005

95% CI

Prec

ipit

ation

(mm

/yr)

Conclusions No statistically significant conclusions can be drawn about assessing potential future predictions.

The increasing trend for thelake levels can be explained by looking at short term fluctuations caused by strong winds, storm surge and ice development in the connecting channels; and long term crustal reboundingand increase consumption use.

Future Work

Look at the mass balance of the whole system and each lake individually to observe the contributing inflows and outflows and see how they have changed through time.

Analyze which factors are statistically important.

Compare the simple regression results with Global Climate Models.

Questions?