The influence of the North Atlantic Oscillation on the sea-level around the northern European coasts reconsidered: the thermosteric effects

Author(s):  
M.N Tsimplis ◽  
A.G.P Shaw ◽  
R.A Flather ◽  
D.K Woolf

The thermosteric contribution of the North Atlantic Oscillation (NAO) to the North Sea sea-level for the winter period is investigated. Satellite sea surface temperature as well as in situ measurements are used to define the sensitivity of winter water temperature to the NAO as well as to determine the trends in temperature. The sea surface temperature sensitivity to the NAO is about 0.85 °C per unit NAO, which results in thermosteric sea-level changes of about 1–2 cm per unit NAO. The sensitivity of sea surface temperatures to the NAO is strongly time-dependent. Model data from a two-dimensional hydrodynamic tide+surge model are used in combination with the estimated thermosteric anomalies to explain the observed sea-level changes and, in particular, the sensitivity of the datasets to the NAO variability. The agreement between the model and the observed data is improved by the inclusion of the thermosteric effect.

2011 ◽  
Vol 75 (3) ◽  
pp. 571-575 ◽  
Author(s):  
José C. Báez ◽  
Juan J. Bellido ◽  
Francisco Ferri-Yáñez ◽  
Juan J. Castillo ◽  
Juan J. Martín ◽  
...  

2015 ◽  
Vol 108 ◽  
pp. 23-36 ◽  
Author(s):  
Margot H. Saher ◽  
W. Roland Gehrels ◽  
Natasha L.M. Barlow ◽  
Antony J. Long ◽  
Ivan D. Haigh ◽  
...  

The Holocene ◽  
2020 ◽  
Vol 31 (1) ◽  
pp. 3-15 ◽  
Author(s):  
Lisa C Orme ◽  
Arto Miettinen ◽  
Marit-Solveig Seidenkrantz ◽  
Kirsi Tuominen ◽  
Christof Pearce ◽  
...  

In recent decades the surface water temperature and salinity in the Labrador Sea have been influenced by atmospheric circulation patterns, such as the North Atlantic Oscillation (NAO), as well as a trend to increasingly warm atmospheric temperatures in recent years. These changes are concerning, given the important role that temperature and salinity have on deep convection in the Labrador Sea. Yet, due to the shortness of available records, the long-term patterns of climate variability in the region are not clear. Here, a diatom-based reconstruction of summer sea-surface temperature (SST) developed from Trinity Bay, Newfoundland, provides insight into variations of SST since 7.2 cal ka BP in the southwestern Labrador Sea. The results show that the Holocene Thermal Maximum (HTM) lasted until c. 5.2 cal ka BP, which was followed by a gradual cooling trend overprinted by centennial temperature fluctuations of 1–2°C. Long-term cooling was likely the result of declining Northern Hemisphere orbital summer insolation, potentially amplified by long-term changes in surface and bottom water salinity, which led to a gradual reduction in the stratification of the water column. Centennial fluctuations in temperature vary in-phase with reconstructed variations in the NAO, supporting a consistent relationship between atmospheric circulation and SST over centennial-millennial timescales. Other factors influencing the SST variability may have been solar forcing during the mid-Holocene and variations in the strength of the subpolar gyre during the late-Holocene. The most prolonged cool period at 5.2–4.1 cal ka BP coincides with sharply reduced salinity in the Labrador Sea and a weakening of deep ventilation in the northeast Atlantic, highlighting a period with altered ocean surface conditions and circulation across the northern North Atlantic.


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