Alexander Korablev:
The Nordic Seas in transformation: evidence from a new climatology and extended dataset
Abstract
Instrumental observations are the only reliable source of information for evaluation of a true variability in the Earth climate system. First trustworthy oceanographic measurements in high latitudes of the northern hemisphere can be dated as far back as beginning of the 19th century. In this study we have gathered and analyzed all available until 2012 data, while majority of the previous analyses are limited by the second part of the last century.
Long-term variability of the thermohaline parameters was inferred using both the in situ data and the gridded fields, which have been computed from uneven measurements by means of modern interpolation technique (DIVA). Monthly and climatological fields of temperature, salinity, density on standard depth levels as well parameters' time-depth diagrams at several key locations in the Nordic Seas and Northern North Atlantic will be publicly available in the form of electronic digital atlas.
Results reveal that variability in the northern North Atlantic and Nordic Seas can be defined as coherent process of anomalies formation, reinforcement, propagation and decay. Within 110 years of instrumental observations we have distinguished steady regimes continuing for decades and events lasted for few years. For instance, predominant low-salinity regime, which was being continued from the early 1970s to the end of the 1990s, was reinforced with two strong low temperature/salinity events of different magnitude and spatial scale spanned for 4-5 years.
Both the abnormal regimes of two-way advection through the Nordic Seas and local atmospheric forcing regimes contributed to the observed variability. The greatest impact seen from the time series and spatial distributions can be linked to alterations in (i) fresh water and sea ice discharge from the Arctic, (ii) Atlantic water inflow and (iii) air-sea fluxes and vertical mixing processes. Time series of Fresh Water Content (FWC), Heat Content (HC) and dynamical highs (DH) in the key areas of the region reveal integral characteristics of the climatic signals propagated through the system. The major driving mechanism behind the observed variability, we believe, closely linked to periodicity of Arctic' ice/fresh water realize/accumulation phases or melting/freezing phases.
Content, technical details and two different approaches utilized for the ongoing Atlas will be also discussed.