1. Distinctive Ocean Interior Changes During The Recent Climate Hiatus how ocean observations tell us about the recent hiatus? Lijing Cheng 1, Fei Zheng 1, Jiang Zhu 1* 1. International Center for Climate and Environment Sciences (ICCES), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China. Institute of Atmospheric Physics, Chinese Academy of Sciences

2. 1. Motivation Where does the heat go? SST-Hiatus 1. Describe how the ocean changes 2. Understand why it changes

3. 1. Data & Models Observations (What happened?) : 1. IGOT,(WOD09-based, QC-ed, CH14-correction) 2. EN4 3. Ishii 4. Argo gridded Model (Why it happened?): CMIP5 simulations, control run, 500years, 7 models including: CCSM4, CESM-CAM5, FGOALS, IPSL, GFDL, MPI, HadCM3 Objective analysis

4. 2. What happened in the ocean? (Observations) 10-years Temperature trend at ocean subsurface Different ocean interior changes are found in this century: 1-100m (cold), 100-300m (warm), 300-700m (cold), 700-1500m (warm) Note: Difference among four datasets is also evident.

5. 2. Results (Observations) 1. The Global ocean changes are controlled by Pacific Ocean 2. Indian Ocean: warming 3. Atlantic: cooling at upper 500m. Which Basin is responsible for the global change ? IGOT Ishii EN4 Argo Focus on Pacific

6. 2.1. Ocean temperature change at upper 300m (Observation) Roemmich 2011 100m 300m Does ENSO variability control the 10-years trend in this century? 1.ENSO is the dominate inter-annual variability in the Pacific ocean. Seesaw along equator thermocline 2. Whether ENSO variability could contribute the 10-years trend? El Nino Warmer Colder

7. 2.1. Ocean temperature change at upper 300m (Observation) 1-300m ocean change may be controlled by ENSO variability More El NinoMore La Nina Why ENSO variability controls 10-years trend in this century? 1.More ElNino at the beginning of this century, more LaNina latter 1.0-100m: Warmer ocean condition at the beginning (ElNino),Colder ocean condition latter (LaNina). 1.101-300m: Colder ocean condition at the beginning (ElNino),Warmer ocean condition latter (LaNina). Tropic Pacific Hypothesis: SST-Hiatus May be simply caused by the change of ENSO statistics

8. 2.1. Ocean temperature change at 1-300m (Observation) Temperature trend from 2004 to 2013 SST-Hiatus 1-100m 101-300m ENSO-like pattern

9. 2.1. Ocean temperature change at upper 300m (Models) Composite Analysis (CMIP5): 1.Identify SST-Hiatus periods (SST-Hiatus: 10-years period with downward SST trend) 2.Count ElNino and LaNina events in Hiatus periods Conclusion: SST-Hiatus is possibly due to the change of ENSO statistics More El NinoMore La Nina Bad news: we don’t know why there are changes in ENSO statistics, maybe due to IPO (Inter-Decadal Pacific Oscillation)? Require further studies

10. 2.1. Ocean temperature change at 301-700m (Observation)

11. 2.2. Ocean temperature change at 301-700m (observation & model) Does ocean change within 301-700m relate to 1-300m? There is not significant correlation between 301-700m Global-averaged ocean change with upper 300m ocean change Imply that it may be different mechanism (not ENSO) responsible for 300- 700m change. Subsurface-Hiatus

12. 2.2. Ocean temperature change at 301-700m (Observation) Temperature trend from 2004 to 2013 ENSO-Like Band-Like Subsurface-Hiatus SST-Hiatus 301-700m 1-100m

13. 2.3. Composite of 301-700m-Hiatis and SST-Hiatus Composite Analysis (CMIP5): 1.Identify SST-Hiatus and Subsurface-Hiatus period (Subsurface-Hiatus: 10- years period with downward 300-700m global-averaged temperature trend) 2. Calculate Global-averaged temperature trend during the two hiatus periods. SST-Hiatus Subsurface-Hiatus Both hiatuses exist in CMIP5 simulations

14. 2.3. Composite of 301-700m-Hiatis and SST-Hiatus SST-Hiatus Composite Subsurface-Hiatus Composite Observation Temperature trend Observations = SST-Hiatus + Subsurface Hiatus

15. Summary Distinctive Ocean Interior Changes are found during recent climate hiatus period: 1-100m Cooling 101-300m Warming 301-700m Cooling/not warming 701-1500m Warming Upper 300m: due to the change of ENSO statistics 301-700m: Another un-known decadal variability 701-1500: Maybe the signal of Global Warming Hypotheses More works are required What happened? Why it happened?

16. “Dragon” is hiding in un-observed ocean ? We are finding “dragon” in the ocean by Argo system By K. Wunsch

17. “Heat” is hiding in the deep, abyssal ocean ? “Some basic elements of the sampling problem are compiled in Table 2. About 52% of the ocean lies below 2000 m and about 18% below 3600 m. By defining a volume as having been ‘probed’ if at least one CTD station existed within a roughly 60x60 km 2 box in the interval 1992-2011 … [A]bout 1/3 (11% of total volume) of water below 2000 m was sampled … Of the 18% lying below 3600 m, about 17% was measured. … [M]any papers assume no significant changes take place in the deep ocean over the historical period … The history of exploration suggests, however, that blank places on the map have either been assumed to be without any interesting features and dropped from further discussion, or at the other extreme, filled with ‘dragons’ invoked to explain strange reports (G. de Jode, 1578).” ─ Wunsch and Heimbach (2014)

18. 2.1. Ocean temperature change at upper 300m (Observation) Trend from 2004 to 2013

19. 2. Results

20. 2.1. Ocean temperature change at upper 300m (Observation) Links between Global ocean temperature change within 1-300m with ENSO variability Correlation between Global-averaged temperature change with Local T change 1-100m 101-300m Understanding the ocean variation at upper 300m