ESTUARINE CONDITIONS AND WATER EXCHANGE IN FJORDS OF PRINCE WILLIAM - - PowerPoint PPT Presentation

A Dissertation by Shelton M. Gay III Texas A&M University ESTUARINE CONDITIONS AND WATER EXCHANGE IN FJORDS OF PRINCE WILLIAM SOUND, ALASKA

Coastal Relief (DEM) of PWS

http://www.ngdc.noaa.gov/dem

Hinchinbrook Entrance Montague Strait

Montague Island Hinchinbrook Island Knight Island Naked Island

Cordova Valdez > 400m > 800m

Introduction

Part A:

• Regional and sub-regional climate
• Physical characteristics of small PWS fjords

Examples of basin types General Variation in hydrography Effects of extraneous (allochthonous) glacial water

• Estuarine conditions in relation to watershed topography
• Principal component analysis of freshwater contents
• Summary and conclusions

Climatic Scenarios in Mid Fall 2009, and Late Winter and Summer 2010

Monthly Mean Air Temperatures and Monthly Precipitation in Sub-Regions of PWS 1994-1998

• Met. Station Locations within PWS

Potato Pt. Cannery Crk. Hatch. Main Bay Hatch. A.F. Koenig Hatch. Mid Sound Buoy Wally Norenberg Hatch. CLAB Buoy

from Gay and Vaughan (2001) Total Annual Precipitation (cm) 1994 1995 1996 1997 Main Bay 413 538 347 501 Cannery Crk. 306 309 205 301

• A. F. Koenig 322 370 225 334

Monthly Total Precipitation in 1991 to 2000 and 2001 to 2010

1991 to 2000 2001 to 2010 Difference between means (+ 7cm) is significant: at the 98% level (p = 0.02) .

Baroclinic-Geostrophic Circulation in Central PWS

Baroclinic-Geostrophic Circulation in Central PWS

Physical Characteristics of PWS fjords

• Examples of basin types

Small to Moderate Secondary Basin: Simpson Bay (9.5km) Moderate Size Secondary Basin: Whale Bay (11.6km)

Moderate Size Secondary Basin: Eaglek Bay (14km)

General Physical Characteristics of PWS fjords

• Effects of Allocthonous Glacial Water

Icy Bay

Icy Bay Columbia Bay

EOS 2010

Cruise track & photos courtesy of Dave Janka

Temperature and Salinity Characteristics of Columbia Fjord in August 2011

Effects of Glacial Water at Whale Bay in 1994

WB11 WB12 WB5 WB3 WB1 WB16

Icy Bay Icy Bay Whale Bay Whale Bay

Glacial Water from Icy Bay Affecting Temperatures in Whale Bay again in 1996

UI2 UI3 UI4 UI5 UI6 UI7 EGB16 EGB1 EGB8 EGB5 EGB3 EGB1

Unakwik Inlet Eaglek Bay Unakwik Inlet Eaglek Bay

Glacial Water from Unakwik Inlet affects Temperatures in Eaglek Bay in 1996 and 1997

Estuarine conditions in relation to watershed characterisitics

Hypotheses:

To test for a significant relationship between the freshwater input and 1) Watershed to fjord basin area ratios (watershed ratios), 2) Watershed size (catchment area), and 3) Watershed elevations (higher = more stored precipitation)

Regressions of FWC to Watershed Ratios in 1994

Eshamy 5.1 Main 4.1 Ewan 3.8 Paddy 2.8 Culross 5.2 Herring 1.2

• L. Herring 2.3

Drier 2.7 South Bay 1.3

• W. Twin

1.6 Whale 2.1 Sawmill 1.9 Twin Bays 0.8 Mummy 2.5 Little 4.8 Bainbridge 2.6 Shelter 2.5 Watershed ratios Watershed ratios

May 94 May 94

Watershed ratios Watershed ratios

June 94 June 94 July 94 July 94

Estuarine Conditions in relation to Watershed Ratios, Maximum Elevations and sizes in 1996

Jack 9.7 Galena 8.5 Zaikof 2.1 Eaglek 2.3 Ewa n 3.8 Paddy 2.8 Drier 2.7 Whale 2.1 Sheep 2.3 Unakwik ~ 17.0 Icy ~12.0 Simpson 6.1

(Aug) (Jul)

Example of Glacial Advection in August 2003

Principal Components of Freshwater Contents

Objectives:

• Quantify the modes of variance in freshwater content anomalies (FWCA) among

fjords (i.e. based on the deviation from the mean FWC profile of all sites).

• Determine how the modes relate to the distribution of FWC and physical

processes within fjords.

• Map the spatial distribution of variance in FWC among sites in PWS.

Principal Components of Freshwater Contents

Results:

• 95 to 99% of variance in FWCA occurs in two statistical modes.
• Mode 1 represents a total freshwater input within a given site, whereas mode 2

indicates the vertical structure of the freshwater content (e.g. stratified by mostly surface input, weakly stratified w/ high sub-surface freshwater or mixed and salty

• ver depth.
• A similar analysis was performed on temperature, but the EOFs are much more

complex and sometimes required > 2 modes to explain 90% of the variance.

60 50 40 30 20 10 30 25 20 15 10 5

SBY SEP MB EB HB LHB DB WB BP FI SHB PWP

Principal Component Amplitude for Mode 1 in June 1994 Principal Component Amplitude for Mode 2 in June 1994

Principal Component Amplitude for Mode 1 in July 1994 Principal Component Amplitude for Mode 2 in July 1994

60 50 40 30 20 10 30 25 20 15 10 5

60 50 40 30 20 10 30 25 20 15 10 5

Principal Component Amplitude for Mode 1 in July 1996 Principal Component Amplitude for Mode 2 in July 1996

• Small fjords with high freshwater input exhibit large, positive mode 1

PCAs, but whereas positive mode 2 PCAs indicate stratification, negative values indicate subsurface freshening.

• In many cases, the effects of local watersheds are superseded by the

advection of extraneous fresh water, particularly from glacial fjords. In at least one case (Whale) the glacial advection creates extreme fresh conditions relative to the WSR in all years.

• In contrast, fjords not influenced by glacial advection have physical

properties mainly determined by local climate, hydrology and, in certain cases, the concentrating effects of high WSRs.

• In 1994, subsurface freshening from glacial advection influenced

hydrographic conditions of small fjords in western PWS, as far south as Flemmng I. and possibly N. Elrington Pass and Sawmill Bay.

Summary and Conclusions

• In 1996, high subsurface FWC was again observed in Whale Bay and

also to the north in Dangerous Pass and two small fjords located in the pass, Ewan and Paddy Bay, indicating that southward advection from glacial regions to the north (or south?) also occurred that summer.

• Similar conditions to the above were observed in Perry Pass in 1994.

• Most small fjords in PWS do not contribute significantly to the

Freshwater Content of the Sound in the spring and summer, and hence have little affect on the baroclinic flow from PWS to the Gulf of Alaska.

• This is instead dominated by advection of water from regions

containing tidewater glaciers.

• More recent hydrography data in PWS and some of the small fjords

from 2006 to 2012 and satellite imagery in 2013 indicate freshwater input from glacial advection within PWS may be occurring earlier than in the previous decade.

• This could be linked to climate changes that are now taking place in

the Arctic.

General Conclusions

Example of Glacial Advection in May 2013

• Most small fjords in PWS do not contribute significantly to the

Freshwater Content of the Sound in the spring and summer, and hence have little affect on the baroclinic flow from PWS to the Gulf of Alaska.

• This is instead dominated by advection of water from regions

containing tidewater glaciers.

• More recent hydrography data in PWS and some of the small fjords

from 2006 to 2012 and satellite imagery in 2013 indicate freshwater input from glacial advection within PWS may be occurring earlier than in the previous decade.

• This could be linked to climate changes that are now taking place in

the Arctic.

General Conclusions

Acknowledgements

 The SEA Research was sponsored by the Exxon Valdez Oil Spill

Trustee Council

 Gratitude is given to the captains and crews of the M/V Auklet, F/V

Miss Kayley and the F/V Kyle David for making the field programs successful.

 Special thanks are extended to all the people who helped collect

CTD data, in particular Loren Tuttle, Nick Peters, Andy Craig and James Thorne.

 Many of the photos in the talk are courtesy of Dave Janka, captain of

the M/V Auklet.

Thanks - Questions