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

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

Coastal Relief (DEM) of PWS Valdez > 800m Naked Island > 400m Knight Island Hinchinbrook Island Cordova Montague Island Montague Strait Hinchinbrook Entrance http://www.ngdc.noaa.gov/dem

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 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 Met. Station Locations within PWS Potato Pt. Cannery Crk. Hatch. Wally Norenberg Hatch. Main Bay Mid Hatch. Sound CLAB Buoy Buoy A.F. Koenig Hatch.

Monthly Total Precipitation in 1991 to 2000 and 2001 to 2010 1991 to 2000 2001 to 2010 Difference between means (+ 7 cm ) 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

Moderate Size Secondary Basin: Eaglek Bay (14km) Small to Moderate Secondary Moderate Size Secondary Basin: Basin: Simpson Bay (9.5km) Whale Bay (11.6km)

General Physical Characteristics of PWS fjords Icy Bay • Effects of Allocthonous Glacial Water EOS 2010 Columbia Bay Icy Bay

Temperature and Salinity Characteristics of Columbia Fjord in August 2011 Cruise track & photos courtesy of Dave Janka

Effects of Glacial Water at Whale Bay in 1994

Glacial Water from Icy Bay Affecting Temperatures in Whale Bay again in 1996 Icy Bay Icy Bay WB11 WB12 WB5 WB3 WB1 WB16 Whale Bay Whale Bay

UI2 UI3 UI4 UI5 UI6 UI7 Glacial Water from Unakwik Inlet affects Temperatures in Eaglek Bay in 1996 and 1997 Unakwik Inlet Unakwik EGB16 EGB1 EGB8 EGB5 EGB3 EGB1 Inlet 0 Eaglek Bay Eaglek Bay

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 May 94 May 94 W. Twin 1.6 Culross 5.2 South Bay 1.3 Main 4.1 Watershed ratios Watershed ratios June 94 June 94 Eshamy 5.1 Herring 1.2 Ewan L. Herring 2.3 3.8 Paddy Drier 2.7 2.8 Whale 2.1 Mummy 2.5 Watershed ratios Watershed ratios July 94 July 94 Little 4.8 Shelter 2.5 Bainbridge Sawmill 1.9 2.6 Twin Bays 0.8

Estuarine Conditions in relation to Watershed Ratios, Maximum Elevations and sizes in 1996 Unakwik ~ 17.0 Eaglek 2.3 Jack 9.7 Galena 8.5 Simpson 6.1 Sheep 2.3 Paddy 2.8 Ewa n 3.8 Icy Drier 2.7 ~12.0 Whale 2.1 Zaikof 2.1 (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 over 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.

Principal Component Amplitude for Mode 1 in June 1994 60 50 40 30 SEP 20 10 SBY HB MB 0 LHB EB DB SHB FI PWP BP WB 30 Principal Component Amplitude for Mode 2 in June 1994 25 20 15 10 5 0

60 Principal Component Amplitude for Mode 1 in July 1994 50 40 30 20 10 0 30 Principal Component Amplitude for Mode 2 in July 1994 25 20 15 10 5 0

Principal Component Amplitude for Mode 1 in July 1996 60 50 40 30 20 10 0 Principal Component Amplitude for Mode 2 in July 1996 30 25 20 15 10 5 0

Summary and Conclusions • Small fjords with high freshwater input exhibit large, positive mode 1 PCAs, but whereas positive mode 2 PCA s 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.

• 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.

General Conclusions • 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.

Example of Glacial Advection in May 2013

General Conclusions • 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.

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