1. Trends in the Western Mediterranean: state of the artCLIVAR ESPAÑA
11-13 febrero 2009 WMED deep waters have warmed and increased its salinity during the second half of the XXth century
WMED intermediate waters have increased its salinity
No robust results have been obtained related to temperature in the WMED intermediate waters
TS TRENDS IN THE WESTERN MEDITERRANEAN: WATER MASS CHANGES AND VERTICAL DISPLACEMENTS (HEAVING)
Patricia Zunino Rodríguez
Manolo Vargas Yáñez
M. Carmen García Martínez
Francina Moya
CLIVAR ESPAÑA
11-13 febrero 2009
1. Trends in the Western Mediterranean: state of the art
CLIVAR ESPAÑA
11-13 febrero 2009 WMED deep waters have warmed and increased its salinity during the second half of the XXth century
WMED intermediate waters have increased its salinity
No robust results have been obtained related to temperature in the WMED intermediate waters
2. How have these trends been estimated?
CLIVAR ESPAÑA
11-13 febrero 2009 Temperature and salinity profiles
MEDAR database (2002)
From 1943 to 2000 500 0 2500 PRESSURE (dbar) 1943 1948 1961 2000
2. How have these trends been estimated?
CLIVAR ESPAÑA
11-13 febrero 2009 100 dbar 500 dbar anomaly + anomaly - TEMPERATURE SALINITY 1991 1991
2. How have these trends been estimated?
CLIVAR ESPAÑA
11-13 febrero 2009 Temperature anomaly 0 0.5 - 0.5 Time (year) 1943 2000 0.006 ºC yr-1 100 dbar Trends on isobaric surfaces don’t necessarily imply water mass changes
3. Contribution to trends in each pressure level
CLIVAR ESPAÑA
11-13 febrero 2009
Changes on isobaric surfaces can be decomposed into:
a. Changes on isopycnal surfaces (changes in water masses)
b. Vertical displacements (heaving, Bindoff & McDougall, 1994)
Both effects could add or cancel, enhancing or masking possible water mass trends in a determined pressure level
3. Contribution to trends in each isobaric level
CLIVAR ESPAÑA
11-13 febrero 2009 1000 dbar Q E - P T, S, = s T, S, = s CHANGE ON ISOBARIC SURFACES
AND
CHANGE ON ISOPYCNAL SURFACES Changes on isopycnals (water mass changes):
Related with the heat and freshwater exchange in the ocean-atmosphere interface
3. Contribution to trends in each pressure level
CLIVAR ESPAÑA
11-13 febrero 2009 wind T T NO WATER MASS CHANGE b. Isopycnal vertical displacement: marine dynamics
3. Contribution to trends in each pressure level
Q E-P Outflow 1000 dbr CLIVAR ESPAÑA
11-13 febrero 2009 T S T ,S, s
V 29.096 Kg m-3 NO WATER MASS CHANGE T ,S, s
V b. Isopycnal vertical displacement: deep water formation
3. Contribution to trends in each pressure level
CLIVAR ESPAÑA
11-13 febrero 2009 dq dt z = dt dq s - dp dt s ∂θ ∂p isobaric
surfaces isopycnal
surfaces heaving This decomposition have never been applied in the WMED,
but it is so common in other world´s ocean How to estimate both contributions?
Bindoff & McDougall [1994]
4. Our results
HEAVING ISOPYCNAL SURFACES ISOBARIC SURFACES CLIVAR ESPAÑA
11-13 febrero 2009 b) Results: Deep layer (600 dbar- bottom)
TEMPERATURE 0.0032 ± 0.0030 ºC yr-1 0.0075 ± 0.0071 ºC yr-1 -0.0057 ± 0.0053 ºC yr-1 29.093 Kg m-3 29.096 Kg m-3 29.099 Kg m-3 -14.02 ± 10.67 dbar yr-1
4. Our results
ISOPYNAL SURFACES HEAVING CLIVAR ESPAÑA
11-13 febrero 2009 b) Results: Deep layer (600 dbar- bottom)
SALINITY 0.0013 ± 0.0010 yr-1 0.0023 ± 0.0021 yr-1 -0.0012 ± 0.0011 yr-1 29.093 Kg m-3 29.096 Kg m-3 29.099 Kg m-3 0.0017 ± 0.0011 yr-1 0.0023 ± 0.0010 yr-1 0.0017 ± 0.0011 yr-1 ISOBARIC SURFACES
4. Our results
ISOPYCNAL SURFACES ISOBARIC SURFACES CLIVAR ESPAÑA
11-13 febrero 2009 b) Results: Intermediate layer (200 - 600 dbar)
TEMPERATURE No significative trend 0.0058 ± 0.0054 ºC yr-1 -0.0048 ± 0.0032 ºC yr-1 29.068 Kg m-3 29.089 Kg m-3 0.0035 ± 0.0030 ºC yr-1 0.0040 ± 0.0038 ºC yr-1 29.068 Kg m-3 29.089 Kg m-3 -4.35 ± 3.45 dbar yr-1 -9.53 ± 9.12 dbar yr-1 HEAVING
CLIVAR ESPAÑA
11-13 febrero 2009
Subestimation of temperature and salinity trends of the deep waters masses when trends were estimated on isobaric surfaces
Intermediate waters in the WMED were warming during the last half century, which wasn't clear before
Upward displacement in the WMED during the second half of the XXth century , and this would be linked to the deep water formation rate in the Gulf of Lions and Levantine basin
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