Norwegian Sea Temperatures Linked To Solar Variation

By Paul Homewood 

 

h/t Kenneth Richards

 

Further to my post showing that the Pacific Ocean was warmer back in the Middle Ages, there was another paper, published in 2010, which linked changes in the temperature of the Norwegian Sea to solar variations.

 

http://onlinelibrary.wiley.com/doi/10.1029/2010JC006264/full

 

 

They find that:

Lowest isotope values (highest temperatures) of the last millennium are seen ∼1100–1300 A.D., during the Medieval Climate Anomaly [Bradley et al., 2003], and again after ∼1950 A.D. The largest and most sustained isotopic increases (coolings) are centered at ∼1500 A.D. and ∼1700 A.D., corresponding to the regional Little Ice Age [Jones and Bradley, 1992]. Isotopic increases at these times are ∼0.3 ‰, indicating decreases of nSST of 1–1.5°C. After smoothing, the amplitude of nSST change over the last millennium is 1.5–2°C.

 

Given the enormous heat content of the ocean, a change of 2C, even just to a depth of 50m, would be expected to have a significant impact on air temperatures at a regional level.

Note as well the reference to “after 1950 AD”.

 

They continue:

The presence of medieval and 20th century warmth and Little Ice Age cooling in our records suggests a possible connection to known solar variations at these times (i.e., the Spører and Maunder minima and medieval and modern maxima, respectively….

On balance, the observed relationship of nSST and solar proxies suggests a climate response to the Sun within the characteristic inertial timescale of the upper ocean, which is one to several decades…

Despite uncertainty in relating solar proxies to absolute variations of the TSI (or the spectral irradiance) [Lean et al., 2002], it is clear that temperature changes of 1–2°C are large with respect to global or hemisphere-scale surface temperature changes expected in direct response to plausible long-term variations of the TSI in the range of 0.1 to 0.4%. The latter equate to changes in radiative forcing of 0.2 to 0.9 W/m² (i.e., top-of-atmosphere TSI*(1–0.3)/4), which may be expected to produce a temperature response of 0.1 to 0.5°C (given, for example, a transient climate response of ∼0.5°C per W/m² [Intergovernmental Panel on Climate Change, 2007]). As simple thermodynamic considerations would lead us to expect smaller temperature changes at the ocean surface than over land, the relatively large near-surface temperature signal we document points to significant regional amplification arising from a dynamical response of the atmosphere-ocean system.

 

They conclude:

We have presented an oxygen isotopic proxy record of near-surface temperature of Atlantic waters from the area of their primary flow into the eastern Norwegian Sea and find that it is robustly and near-synchronously correlated with various proxies of solar variability spanning the last millennium. The associated decade- to century-scale variation of estimated nSST ranges from 1 to 2°C, significantly larger than expected based on thermodynamic considerations alone. We suggest that this is due to a solar influence on the regional modes of atmospheric variability which, in turn, control the poleward transport and temperature of warm Atlantic surface waters.

 

To sum up, it is clear that it is the sun, and not CO2, that is the dominant force when it comes to ocean temperatures, and that solar variation links together both the medieval and current warming periods, as well as the Little Ice Age.