Tropical ocean climate during the LIA and MWP: Mud drift sediments in the East China

Sea and more regional data synthesis

Min-Te Chen**National Taiwan Ocean University

Corroborators: Masanobu Yamamoto, Shengfa Liu, Xuefa Shi,Yusuke Yokoyama, Xiaopei Lin, Hong Yan, and ---

4th Asia 2K Kyoto

2K climate in the WP

• LIA: cold / dry (terrestrial)• MWP: warm / humid (terrestrial)• Asia Monsoons weak in LIA & strong in

MWP (only one cave record, Wanxiang shows it, Zhang et al., 2008)

• Why WP marginal seas? It fills out the data gap of the Eastern China, and is important to know how it affect the settlements adjacent to the seas, fisheries, aquatic activities, etc.

• Marine sediments provide multi-proxy records of SST and salinity (precipitation), productivity, etc..

• However, the sediments maybe more age uncertain, relying on 14C dating, and often bioturbated so give dampened results ;

• Stable high sed rate cores (coast & mud drifts) now show large changes of LIA and MWP climate but complicated by local hydrology --

2K climate in the WP

Coastal & Mud Drift Sediments in the WPExtensive Shelves

High Sedimentation Rates

Heavy Precipitation

• MZ01 (120°50.94'E, 26°32.82'N), a gravity core taken from a mud drift area near Fujian coast (core length 2.96 m; water depth 64.7 m.

• Monsoon precipitation in the drainage areas.

• Strong winter monsoon driven CCC transports annually exported sediments from the Yangtze and Yellow Rivers into ECS shelves.

• SSTs are determined by the monsoon wind (Ekman transport), the CCC and Kuroshio front, and water stratification (barrier effect)!.

Study Area & Samples from ECS shelves: heavy precipitation and huge sediment flux output from Yangtze, Min, Choshui Rivers

• Age model by 13 AMS 14C dating (benthics) indicates an averaged sed. rate ~ 36 cm/kyr. (Multi-decadal resolution!?)

Uk’37 SST

- Brassell et al., (1986): established relationship between alkenone unsaturation & upper ocean temperature

- Prahl and Weakham (1987): Uk’37 index = [37:2] / ( [37:2] + [37:3] )

- Alkenone-producing alage: Emiliania huxleyi and Gephyrocapsa oceanica

- Advection Transport & Species Variarion: First appearance datum of E. huxleyri - 256ka

- Calibration Equations: Uk’37 index = a*SST(oC) + b

- Regional Equation (South China Sea): Uk’37 index = 0.031*SST(oC) + 0.092 (Pelejero & Grimalt., 1997)

- Global Equation: Uk’37 index = 0.033*SST(oC) + 0.044 (Muller et al., 1998)

TEX86=

(Schouten et al., 2002)

TEX86=0.015×SST＋ 0.028

Crenarchaeota

(Hopmans et al., 2004)

Range : 0~10 1

terrestrialmarine

TEX86 SST: but reflect subsurface temperature

Errors in average -- • SST ±1°C• Age ±100 yrs

MZ01 2K SST errors linearly related to age errors!

SSTerror = Σ [(SST-SSTEEMD)2]1/2 x Ageerror / Σ (Ageerror/n)

WP 2K data to be submitted!

• MZ01 (this study) - sediments• ODP 1202 (Wu et al., 2012)• MD972146 (Lin, Chen et al., 2013; 2014) - sediments• Leizhou & Xisha (Hong et al., 2015) – Porites lutea, Tridacna gigas

2K criteria:- At least one numerical age per 500-year interval- At least one analysis every 200 years- Must span 500 years during the past 2k

MD972146

(Yang et al., 2002) MWP LIA

1°C

100 yrs

(Wu et al., 2012)

MWP LIA

1°C

100 yrs

(Yan et al., 2015)MWP LIA

1°C

100 yrs

(Lin, Chen et al., 2013; 2014)

MWP LIA

1°C

100 yrs

(Oppo et al., 2009)MWP LIA

1°C

100 yrs

WP 2K SST patterns

• Here we contribute a new WP SST 2K data set.• While focusing on the LIA and MWP: mud drift core

near East China show SST changes with more warming in early LIA and cooling in the early MWP (which may result from fresh water barrier layer effects)

• WP open oceans (SCS and WPWP, low resolution!) show cooling in the LIA and warming in MWP (but the magnitudes are determined by the nature of paleoclimatic archives, oceanic setting!

• Keeping going to form a new marine sediment proxy data base of western Pacific marginal seas --

• More contribution to the future 2K studies --

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WEPAD (Western Pacific Drilling):• 3rd working group meeting – May 18-19, 2015, Jeju, Korea (You are welcomed!)

Sea surface salinity (SSS) pattern suggest the possibly more important barrier layer effects during strong winter monsoon seasons (data provided by Xiaopei Lin, OUC)

January July

Hydrography and Water Stratification: Barrier Layer effect ->increased fresh lens

prevent mixing and cause surface warming!

Sea levelChina

West East

China Coastal Current

Taiwan Warm Current

MZ-1