Perspectives for SO research during the next five years

Transcription

1 CLIVAR SOP meeting Perspectives for SO research during the next five years K. Katsumata (JAMSTEC)

2 Link between changing forcing and SO Forcing & responses are observed with various certainty Link between forcing and responses are not understood

3 Changes in forcing SAM Mean zonal wind stress between 50 S and 60 S 0.2 (Pa) OFES K7 SODA SAM-related wind changes Glacial melt Air-sea fluxes Fig. 1 Basal melt rates of Antarctic ice shelves.color coded from < 5 m/year (freezing) to >+5 m/ year (melting) and overlaid on a 2009 Moderate Resolution Imaging Spectroradiometer mosaic of Antarctica. Cerovečki et al., 2011 E Rignot et al. Science 2013;341: Published by AAAS Rignot et al., 2013

4 Responses Freshening AABW Sokolov and Rintoul (2009) Aoki et al., (2005) Rintoul et al., (2007) Contracting AABW S ward shift of fronts Steady ACC transport (BC) (a) TW+IW (b) UCDW+LCDW 35 Eddy saturation (c) BW MOC? Transport (Sv) Purkey and Johnson (2012) Böning et al. (2008) Katsumata and Masuda (2013) Meredith and Hogg (2006)

5 Missing links Enhanced zonal wind & eddy activity, ACC transport Enhanced zonal wind & MOC S'ward shift of zonal wind & ACC Ice melt & AABW property/quantity etc...

6 Example AABW property Icescape change & AABW Potentially important for global GPE budget! (Hughes and Griffiths, 2006)

7 40 S 120 E 130 E 140 E 60 S 50 S 60 S 120 E 140 E Ross Sea Dibble io n ss re D ep ie ev 0 E Ad él 100 E George V Land ar Cape Poinsett La z 70 S 80 E Tr ou gh 65 S Mertz (m) Possible ventilation change? 0 Dibble and Mertz Polynyas

8 Near-bottom DO changes 0 km 1000 km 2000 km 3000 km 2000 n (kgm 3 ) (dbar) 150 E 140 E 130 E 120 E 110 E 100 E 90 E (a) E 105 E 120 E 135 E µmol/kg Dissolved oxygen (µ mol/kg) (dbar) 0 km 1000 km 2000 km 3000 km (b) E 105 E 120 E 135 E

9 Change in source water mixing ratio ( C) E 140 E 130 E 120 E 110 E AABW = αaabw + βrsbw + (1-α-β)RSBW E 90 E S (psu) RSBW in 2000 RSBW in 1990 ALBW in 2000 ALBW in 1990 Source water data from Williams et al. (2010)

10 Marin et al. (2007) Ross Sea B-15/C-19 events (2000, 2002) Possible changes to observed RSBW changes?

11 Link between changing forcing and SO Forcing & responses are observed with various certainty Link between forcing and responses are not understood

12 Japanese platforms for SO 白瀬 Shirase Cheng1, Yasushi Fukamachi2, Shigeru Aoki2, Shuki Ushio3, Kay I Ohshima2 海鷹丸 Umitaka kyo, Japan. 2. Hokkaido Univ., Sapporo, Japan. 3. National Institute of Polar Research, Tokyo, Japan. 白鳳丸 HakuhoSea ice production 未来 Mirai Sal. Aug. Ma Average m/year Oct. Jul. Apr. J F J F M A M J J A S O N D J J A S O N D Time Lag? Jun. Mar. (2012) proposed that the f Cape Darnley is the 4th AABW, and dense shelf water, ABW eventually, is produced ape Darnley polynya. Sea ice production began at March, that is, about two months earlier than the first signal of AABW at 3000m depth. unt of AABW in Antarctic te production volume and h polynya region. A M Time variation of sea ice production at Vincennes Polynya. Discussion with Box model Salinity flux Sf are estimated from sea ice producion data IP. Volume of shallow region V=100km 150km 100m = m3 Mooring system 1) Initial condition Averaged salinity in the box is supposed to be S=34.0. T= 1.9 n => Not dense enough to sink Sal. Daily input of salinity S (kg) = IP Chain5m 5m ) 130 days May 10 S Denser than that of MCDW( n=28.27) 13mm US 5/8 Chain2m 2m 80m Nylon 180m M Distribution of sea ice production estimated from satellite data. round Antarctica. Sep. US1/2 10m Nylon 30m MicroCAT MicroCAT 5m SUS Nylon 100m 100m SUS3 mm Average value of salinity Sn( ) in the box Sn=Sn 1+Sf/( V) US1/2 5m Nylon 5m 5m 30m US1/2 2m Time variations of salinity and density in the box (100 km 150 km 100 m) were examined by integrating salinity flux c S= S 34.5 Start of sea ice production a ) 138 days = May 18 S > n > n b SUS m A/R 28.3 RCM11 SUS SUS SUS 10m Nylon RCM8 AABW property off 27.8 D Density range of AABW n Density range of MCDW

13 Cape Darnley Project Year H H H34 Cruise Aurora Hakuho- Maru Hakuho- Maru? Integrated tracer Obs. Region Slope Abyssal Plain Oxyg Wild High ice Mooring line Hydrography lines CFC Depressio

14 R/V Mirai 20/17 cruise CTD (T, S, PAR, Turbidity, DO) Sampling (C items, nuts, CFC/SF6, density etc.) L-ADCP, microstructure?

15 Recent outputs Cape Darnley Ohshima, et al. (2013) Vincennes Polyna S4I revisit Kitade et al. (2014)