Warn and cold-core anticyclonic eddies in the western subarctic North Pacific

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Properties of anticyclonic eddies in WSAG (Itoh and

1 Warn and cold-core anticyclonic eddies in the western subarctic North Pacific S. Itoh, I. Yasuda & H. Ueno I. Properties of anticyclonic eddies in WSAG (Itoh and Yasuda, JPO, in press) II. East-West comparison of anticyclonic eddies

2 Important roles in transporting heat, materials, and biota Warm anticyclonic eddy (Kuroshio warm-core ring) AQUA MODIS: 21 MAY 2009

3 Anticyclonic eddies (AEs) in the Kuroshio-Oyashio Extension region Itoh & Yasuda (2010 JPOa): Quantified eddy characteristics using altimetric data Anticyclonic eddies (AEs) Propagate northward along the J & KK trenches Problem Warm- and cold AEs (e.g. Yasuda et al. 2000) were not distinguished Vertical structure information is needed to examine their roles in transporting heat & materials 50 N 45 N 40 N 35 N HKD OY1 JT OY2 KI KE 30 N 140 E 150 E 160 E 170 E KKT Trajectories of AEs (Itoh & Yasuda 2010)

4 Objective (On AEs in WSAG:) To clarify water mass structure of anticyclonic eddies in the western subarctic North Pacific Distributions of warm and cold AEs Temperature/Salinity properties ERS JASON T/P ETC. ARGO JMA R/V HAKUHO-MARU

5 Jason and Argo 1963 Film by Harryhausen Present Study: another adventure Jason, T/P, ERS, etc., with Jason and Argonauts on their ship Argo in situ observations, WOD05, and Argo

6 Data and Methods Data SSH anomaly: AVISO Profile data: Argo, WOD05, & observations by ourselves Methods AEs are detected from SSHA 50 N 45 N Hokkaido Sea of Okhotsk Kuril Islands Profile data near the detected center of AEs are retrieved Anomalous water properties from climatology (WOA01) are estimated 40 N North Pacific 35 N 140 E 145 E 150 E 155 E

7 Distribution db Heat C db Heat C. 45 N 45 N Heat content [J m 2 ] 40 N 35 N 140 E 145 E 150 E 155 E 40 N 35 N 140 E 145 E 150 E 155 E < < < < < Distribution of warm and cold AEs based on heat content anomalies

8 Classification 45 N 40 N Between Kuroshio and Oyashio Oyashio area 35 N 140 E 145 E 150 E 155 E Area classification

9 Depth [db] Group I (Area between K & O) 0 P. Temperature Salinity 0 Vertical profiles vs pressure [ C] S [psu] Warm & Saline anomalies above 400 m (reflecting Kuroshio properties) Fresh anomalies below 400 m Measurements Mean S. E. Climatology Cold and fresh anomalies around σθ Potential density [σ θ ] P. Tempearture Salinity Vertical profiles vs σθ (below the upper core) [ C] S [psu]

10 Depth [db] Group IIw (Warm eddies in Oyashio area) 0 P. Temperature Salinity 0 Vertical profiles vs pressure [ C] S [psu] Warm & Saline anomalies above 200 m Fresh anomalies below 200 m Measurements Mean S. E. Climatology 26 P. Temperature Salinity 26 Cold and fresh anomalies around σθ Potential density [σ θ ] Vertical profiles vs σθ [ C] S [psu]

11 Depth [db] Group IIc (Cold eddies in Oyashio area) P. Temperature Salinity Vertical profiles vs pressure Cold above 400 m Fresh anomalies from surface to 1000 m [ C] S [psu] Measurements Mean S. E. Climatology Cold and fresh anomalies around σθ Potential density [σ θ ] P. Temperature Salinity Similar to Okhotsk water Vertical profiles vs σθ [ C] S [psu]

12 Evolution & interaction of (a) OY KE CAE OSW EKC warm & cold OYW anticyclones (a) Warm eddies from KE in the south, with moderately cold Oyashio water below, and cold eddies from Okhotsk in the north (b) WAE (b)a warm eddy propagates northward to interact with a cold eddy (c) (c) The two eddies are coupled: the process called Alignment (Polvani, 1991)

13 06 East-West comparison Number CHELTON ET AL.: GLOBAL OBSERVATIONS OF OCEANIC EDDIES OBAL OBSERVATIONS OF OCEANIC EDDIES Amplitude L15606 Looking into subarctic gyres of the North Pacific, Eddies are far richer and stronger in the west than in the east (despite the L15606 underestimation in the west; Itoh & Yasuda, 2010a) Eddies are detected along the coast in the east re 3. The eddy characteristics in 1! squares for eddies with lifetimes!4 weeks: (a) The number of eddies of both ities (white areas correspond to no observed eddies); (b) the mean amplitude; (c) the mean diameter; and (d) the entage of SSH variance explained (white areas correspond to 0%). The contour in each panel is the 4 cm standard ation of filtered SSH. From Chelton et al. (2007) (both cyclones and Anticyclones)

14 Anticyclonic eddies Anticyclonic eddies in the East (Gulf of Alaska) 60 o N 65 o N 40 o N 35 o N Anticyclonic eddies in the West 50 o N 45 o N 140 o E 55 o N Kashiwa Joban Kuril eddies Sanriku 150 o E Kushiro Bussol Kamchatka 160 o E Aleutian Kuroshio WCR 170 o E 45 o N 50 o N 170 o W 55 o N 180 o W Alaskan Stream 160 o W Kenai 150 o W Yakutat Sitka 140 o W Haida 130 o W Crawford, 2005; Ladd et al., 2005; Henson & Thomas, 2008; Ueno et al., 2009; Rovegno et al., 2009 Lobanov & Bulatov, 1993; Yasuda et al., 2000; Rogachev, 2000; Rogachev et al., 2007; Itoh & Yasuda, 2010a,b 120 o W Portland

15 Properties Mean (maximum) value West East Kuroshio Kuril Haida / Sitka / Yakutat / Kenai / AS Core water Upper: W/S Lower: C/F Cold & Fresh Fresh (warm/cold) Origin Upper: Kuroshio Lower: Okhotsk Okhotsk Sea Coastal water >> < SSH amplitude 26 (88) cm 11 (41) cm 24 (53) cm Core radius 61 (99) km 46 (71) km 53 (113) km >> < Lifetime Propagation 40 (167) weeks N NE O (1km/day) 32 (115) weeks >> ~ S SW O( 1km/day) 32 (131) weeks ~ 5yr W of 160W W2.3 ( ) km/day Crawford, 2005; Henson & Thomas, 2008; Ueno et al., 2009; Rovegno et al., 2009; Itoh & Yasuda 2010 a, b

16 Formation processes Kuroshio WCR (upper core) Shed from a wind-driven gyre (wind-driven) GOA Eddies Kuril Eddies Originated from well-mixed coastal water (density-driven) Transport subtropical water northward (with iron rich? water in the intermediate layer) Transport iron-rich coastal water offshore Crawford, 2005; Di Lorenzo et al., 2005; Johnson et al., 2005; Ladd et al., 2005; Rovegeno et al., 2009

17 Summary Warm and cold anticyclonic eddies in WSAG 85% of AEs have a warm core in the upper layer The warm eddies have a cold/fresh lower core in the intermediate layer of σθ. Alignment of Kuroshio WCR & Kuril eddies? East-west comparison Richer in west than east Similarities in properties & formation processes between Kuril eddies and GOA eddies

Impact of Alaskan Stream eddies on chlorophyll distribution in the central subarctic North Pacific* Hiromichi Ueno 1,

October 23, 2009, 10:15-10:35 PICES 2009 Annual Meeting ICC, Jeju, Republic of Korea Impact of Alaskan Stream eddies on chlorophyll distribution in the central subarctic North Pacific* Hiromichi Ueno 1,