IUGG Sapporo Michael Steele Polar Science Center APL

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 A new view of summer Pacific in the Arctic Ocean Water Michael Steele, Jamie Morison, Wendy Ermold, Ignatius Rigor, & Mark Ortmeyer Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA 98105 USA Koji Shimada Jamstec Marine Science and Technology Center, Yokosuka, Japan surface layer summer Pacific water T S Atlantic layer SCICEX’ 96 (cast 43)

Michael Steele Polar Science Center / APL University of Washington IUGG Sapporo Lateral extent of summer Pacific water July, 2003

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 Why do we care about Pacific water? Ø Global freshwater circulation Ø Major component of the Arctic Ocean halocline Ø “Nutrient river” through the Arctic Ocean North Water Polynya Tremblay et al. (2002)

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 Water masses in the Bering Strait region …following Coachman et al. (1975) & others Bering Sea Water (BSW) Alaska Coastal Water (ACW) Siberian Coastal Current (SCC) Alaska BDI LDI Russia Gulf of Anadyr Water (GAW) Bering Shelf Water (BSW) BSW : colder, salty, high nut’s ACW : warmer, fresher, low nut’s

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington There are 2 July, 2003 types of summer Pacific water in the Arctic Ocean! “BSW” T S …Shimada et al. , 2001 l ACW: Alaskan Coastal Water u s. BSW: summer Bering Sea Water

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 How far downstream can we detect a summer Pacific water Tmax ? NPEO = North Pole Environmental Observatory At least as far as the area north of Ellesmere Island. . . …but is this true for all years? …and what exactly is getting there: s. BSW? ACW?

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 Hydrographic surveys http: //psc. apl. washington. edu/northpole Twin Otter tent Years 2000/03 stations CTD & bottle obs …NPEO also includes drifting buoys + moorings

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 1993 Summer Pacific water: vs. Tmax z

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 Schematic circulation of summer Pacific water in 1993 s. BSW Alert …a “separated flow regime” w. r. t. Pacific water

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 The area north of Alert, Ellesmere Island: Iceshelf (Newton & Sotirin, 1997) + NPEO (Steele et al. , 2003) s. BSW Tmax (north of Alert )

Michael Steele Polar Science Center / APL University of Washington IUGG Sapporo July, 2003 Summer Pacific Water circulation: Low (1980’s) vs. High (early-mid 1990’s) AO index § Mixed summer Pacific water regimes throughout the Arctic Ocean …including in outflows through the western Canadian Archipelago? § Old (i. e. , no Tmax) s. BSW north of E. I. § Separated summer Pacific water regimes in some of the Arctic Ocean …including through western/ eastern Canadian Archipelago channels? § New (i. e. , warm Tmax) s. BSW at EISB

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 What about chemical tracers? Pacific water (%) in the upper 30 m (using the N/P ratio). 50% ’ 93 – ‘ 96 ’ 00 – ‘ 01 K. Falkner, OSU Jones et al. (1998) AO index drops through the latter 1990’s Transpolar Drift Stream has less Pacific influence Confirms our T/S data. But there’s more to do…

Michael Steele Polar Science Center / APL University of Washington IUGG Sapporo July, 2003 What about interannual variability in the source of these waters? high variance low variance

A new NSF-funded project: Circulation in the “Freshwater Switchyard” of the Arctic Ocean 3 project components: 1. Large-scale hydrochemical sections (Schlosser + Smethie) 2. Boundary current section at the slope (Steele) 3. Sea ice transport studies (Kwok) Obs: spring 2003 -2007

Switchyard slope section’ 03 Continental slope The isopycnals are nearly flat! very little vertical shear …I need to look at the wind/ice stress forcing

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 The End… Thanks to colleagues at PSC, IOS, & elsewhere for data and ideas!

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 And now, for the obligatory Arctic Oscillation discussion… AO index positive neutral negative Negative AO index: The sea ice response Chukchi Sea -> Ellesmere Island: ~6 years Positive AO index: Chukchi Sea -> Ellesmere Island: ~3 years

Switchyard and NPEO sections

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 A new look at T(z) profiles in the Canadian Basin of the Arctic Ocean, especially under AO+ conditions. There’s 3 Pacific water types: ACW Summer BSW Winter BSW …is there “winter ACW? ” Ø T & S data say “no” ØT, S, O 2 data (Itoh & Shimada, 2003) say maybe…

Michael Steele Polar Science Center / APL University of Washington IUGG Sapporo July, 2003 What about interannual source variability? ! Aagaard, Woodgate, & Weingartner http: //psc. apl. washington. edu/HLD/Bstrait/bstrait. html There’s a lot of it! …not to mention variations in the Chukchi Sea.

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 Why don’t we see this in our data, downstream from this (highly varying) source? (Part 2) 1996 + 1997 1993 warmer? There’s some evidence for source variability downstream in the Arctic Ocean, but: Our observations are explainable mostly by changes in circulation, rather than by changes in the character of the inputs.

IUGG Sapporo Michael Steele Polar Science Center / APL University of Washington July, 2003 What’s the role of the North American boundary undercurrent? Lots of question marks… Limited evidence suggests a deep eastward current, with interannually varying vertical shear in the halocline. This high interannual variability in the transport of halocline water masses within the current

Details Alert-NP survey: Twin Otter aircraft, 6 -9 stations “THICR” = THrough-Ice CTD-Rosette, measuring T, S, O 2, oxygen isotopes, tritium/3 He, CFC’s, barium, & nutrients. Samples to be drawn at Alert. Boundary current survey: helicopter, 6 -9 stations CTD-O, XCP, surface layer bottles. Sea ice transport studies: satellites uice: AMSR passive μwave, ENVISAT SAR; hice: altimeters on Ice. SAT (laser) & ENVISAT, Cryo. SAT (radar) …modified from Newton & Sotirin (1997)

Switchyard slope section’ 03 BSW / ACW ? Summer Pacific water Tmax: Ø It’s recovered, but still cool Ø S ~ 32 on the slope Ø S > 32 on either side NPEO station #6 Tmax slope Tmax’s

The “freshwater switchyard”: A good place to detect the origins of freshwater that’s about to leave the Arctic Ocean Large-scale sections Boundary current section …based on Jones et al. (1998); Steele & Boyd (1998); Proshutinsky et al. (2002); Rigor et al. (2002) 3 project components: 1. Large-scale hydrochemical sections (Schlosser + Smethie) 2. Boundary current section at the shelf break (Steele) 3. Sea ice transport studies (Kwok) Obs: spring 2003 -2007