1. The Woods Hole – Hawaii Ocean Time-series Station (WHOTS)
Roger Lukas, Robert Weller and Albert Plueddemann
WHOTS is a collaboration between WHOI, UH and PMEL, with cooperative NOAA and NSF funding. Through OceanSITES and JCOMM, WHOTS is part of a global network of time-series sites.
sustained observations, new understanding, departures (surprises!) from either climatologies, models, or previous understandings
deep T/S variability would challenge us all to think carefully about deep T/S obs
The attempt to develop and maintain metadata standards through OceanSITES and JCOMM Ops is yet another thread.
ERA Interim comparisons for met/flux highlights and description of salinity changes (and maybe PWP runs if you have them)

2. WHOTS is an element of NOAA’s Ocean Reference Stations
part of the OceanSITES & JCOMM OPS international network
leverages long record and context from HOT (e.g. carbon and salinity/hydrological cycle)

3. trends, ENSO and annual cycle resolved by HOT pCO2
Mauna Loa
eddies and storms are not resolved by HOT but are resolved by WHOTS
ALOHA/HOT pH
Figure from PMEL ocean carbon website
pCO2 water
pCO2 air
from PMEL ocean carbon website

4. WHOTS surface buoy (real-time)
U, T, RH
Radiation (soon in water, Laney/WHOI)
Rainfall
Near-surface ocean T
pCO2 air and water; pH (PMEL)
Need wave spectrum
Mooring (delayed mode)
u, T, C, S, P [0-155 m]
near-bottom microcat to be added
Sun-stimulated fluorescence on ocean moorings
Collaborators: Dr. Robert Weller, WHOI Physical Oceanography Department Dr. Al Plueddemann, WHOI Physical Oceanography Department I received a 2009 NASA New Investigator award to begin long-term, ocean color radiometric time series on open ocean moorings. My main interest in this is to better unerstand short-term and seasonal variability in the diurnal pattern of sun-stimulated phytoplankton fluorescence. An abovewater, five-radiometer sensor suite is being integrated into the WHOTS8 mooring to be deployed at Station ALOHA off Oahu in fall This suite will record spectral water-leaving radiance as well as incident spectral irradiance, and telemeter these data to shore using an Iridium link. In addition, three underwater on the mooring will measure chlorophyl lfluorescence at three depths in the euphotic zone, to assess diurnal variability in fluorescence quenching.

5. T
4750 m S

6. Large Salinity Trends and Variations
1950
2000
WHOTS
35.5
sea surface salinity @ Koko Head
SSS @ ALOHA
34.5 z
fully-resolved temporal sampling
HOT 25
35.4
potential density (kg m-3) 26
decadal variations
long-term trend (disrupted ) 27
1950
2000
historical hydrographic profiles within 200 km of ALOHA
(note gaps) 34
HOT cruises present

7. Salinity Trends on Isopycnals
Freshening σθ ( m)
Max /decade large!
The freshening signal is very robust on isopycnal surfaces, filtering out noise from internal waves
Smaller signal, but correlated with O2 and nutrients
The freshening signal is very robust on isopycnal surfaces, and about twice as large.
Large upper pycnocline decadal variation since 2007 has disrupted mid-pycnocline trend 7

8. 20-Year Long Thermohaline Trends @ ALOHA
θ(z)
S(z)
Warming over much of upper ocean (x m!)
Peak warming m (Smax), not at surface
Cooling below 700 m
Salinity increasing in upper 200 m
Freshening in the thermocline
0.16/decade
0-100 m density ↑; density ↓
Stratification ↓ in upper ocean!
deeper mixing  productivity
0.4 °C/decade
Density decreased in the upper 1000 m, except in the upper 100 m where the warming trend (~0.16K/decade) was more than offset by increasing salinity. The largest density decreases were in the m range. The maximum warming was at 180 m (~0.4K/decade), with a peak cooling around 250 m. The density decrease near 250 m is due to a freshening trend of -0.06/decade. This freshening is clearly due to advection (see later isopycnal analysis). The broad warming between dbar peaks at ~0.17K/decade, comparable to the surface layer warming. A freshening trend of about -0.02/decade also occurred between m. From m, temperature decreased over the observational period. Deep and abyssal trends in temperature and salinity are also revealed in the HOT record. Below 1500 m potential temperature, salinity and potential density all increased.
Note that the fraction of variance (r2) explained by the regression is highly significant upper 200 m, but remains significant below. (DoF ~ 217 – 8) 8

9. Salinity plays an important role in stability of upper ocean on interannual and decadal time scales, with effects on mixing and productivity (Corno et al., 2007; Bidigare et al., 2009)
WHOTS
HOT CTD photo

11. Evaporation: Comparison of WHOTS with ECMWF-Interim
decorrelation scale for evaporation large relative to reanalysis grid scale
important biases in mean and variance of ECMWF analyzed evaporation
daily averages

12. Precipitation: WHOTS net evaporative regime
Sean Whelan (WHOI)
net evaporative regime
Rainfall small space-time scales
Not well-observed from space
Poorly represented in NWP model-reanalyses

13. WHOTS mixed layer salinity compared to WHOTS freshwater fluxes
mixed layer depth variations contribute to mismatches between these two curves
trend removed from net cumulative P-E
(the freshwater needed to balance must arrive from higher latitudes directly via surface currents, or be entrained into the mixed layer at ALOHA after transport in the upper pycnocline

14. Integrated net heat flux into 50 m layer
Clearly, cold and salty water must be transported into the surface layer at ALOHA by some combination of horizontal advection, upwelling, and vertical mixing to provide a mean balance – how much do they contribute to interannual – decadal variations?

15. comparison of MLD from WHOTS mooring (colored lines) with estimates from CTD profiles during HOT and WHOTS cruises

16. Modified Price-Weller-Pinkel mixed layer model forced with WHOTS air-sea fluxes
WHOTS mooring
mixed layer depth

17. enhanced shear  vertical mixing
lateral eddy transports??
interannual variations of eddies

18. Summary Sustained, collaborative, multi-disciplinary science
Air-sea fluxes, ocean-truthing atmospheric reanalyses, forcing and benchmarking ocean models
Upper ocean climate – hydrological cycle
Eddies and ecosystem dynamics
Impacts as part of a global observational network
Assessing ocean changes (incl. C) and enabling climate predictions
Atmosphere and ocean modeling – Ocean Reference Stations
Institutions and agencies must sustain infrastructure
Sustained multi-institutional collaboration (WHOI, UH/SOEST, PMEL)
Collaborative funding, NOAA, NSF and State of Hawaii
OceanSITES data management (setting metadata standards)  WHOTS subsurface incl. V though mid-2011

19. Thank You! WHOTS data are available via http://uop.whoi.edu
ftp://ftp.ifremer.fr/ifremer/oceansites/
ftp://data.ndbc.noaa.gov/data/oceansites/

25. Steric Height @ ALOHA Comparable to Hawaii tide gauges
0/1000 dbar cm/decade (all casts) cm/decade (annual averages) 80/1000 dbar 1.6 cm/decade (with and without averaging) mixed layer salinity increase overcompensated warming
Comparable to Hawaii tide gauges
Dynamic height (0/1000 dbar) increased ~2 mm/yr, comparable to mean sea level changes in the Hawaiian Islands, and to estimates of the thermal expansion contribution to global mean sea level rise. Changes in both temperature and salinity were significant contributors, however.
1.6 mm/yr 1.6 cm/decade 25

26. thermosteric height trend 1962-2001 halosteric height trend 1962-2001
Ocean dynamics are important – subtropical gyre intensification, thermocline/halocline displacements
thermosteric height trend
halosteric height trend
-13 – +13 mm/yr
-8 – +8 mm/yr
Kohl and Stammer (2008)
FIG. 1. (a) Model SSH trend and (b) steric SSH trend estimated over the 40-yr period 1962–2001. A global mean trend of 0.74 mm
yr1 was removed from the steric trend. Corresponding (c) thermosteric and (d) halosteric sea level change including the global mean
trend of 0.92 and 0.18 mm yr1, respectively. All fields are in cm yr1.
Salinity important for determining SL changes due to ocean density changes (Kohl and Stammer, 2008) 26

27. Salinity trends on Isopycnals water on heavier isopycnals comes from farther away (Δpsu/50 yrs)
24 σθ
25 σθ
Durack and Wijffels (2010) Fig. 10
26.75 σθ
27.5 σθ
Durack and Wijffels (2010) 27

28. Acidification @ ALOHA DIC Maximum not in surface layer
Updated and adapted from Dore et al. (2009, Proc Natl Acad Sci USA 106:12235 )
Maximum not in surface layer
DIC
pH of surface ocean
Annual, interannual, decadal and longer term changes in surface forcing, mixing, and advection
Local and remote physics are crucial, not just pCO2, temperature and biology
In addition to understanding physical climate variations in the North Pacific Ocean, we need to understand how biogeochemical variations are affected by physics. We can understand the acidification of the mixed layer as a result of being nearly in equilibrium with increased atmospheric CO2, although entrainment of less alkaline waters is important on some time scales. However, subsurface pH trends cannot be understood so easily. While confidence intervals are large, there is apparent vertical structure in these trends, and some reasons to believe that they are real.
pH trend vs depth pH
This point was made in the paper 28

29. Subduction of ML salinity anomalies + anomalous subduction
Evolution of a fresh/cold anomaly
Sasaki et al. (2010) Fig. 2
Analysis of Argo float data Sasaki et al. (2010, GRL); see also Ren and Riser (2010, (Deep-Sea Research II – Suginohara memorial issue) 29

30. Salinity Trends on Neutral Surfaces
zonally averaged salinity trends (Δpsu/ )
70 S
70 N
Durack and Wijffels (2010) Fig. 9b
Durack and Wijffels (2010) 30