Seawater properties and Ocean Heat Content in in Kongsfjorden, Svalbard S.Aliani, R. Sciascia, A. D’Angelo, F. Del Bianco, F. Giglio , L. Langone and S. Miserocchi CNR-ISMAR, Italy (stefano.aliani@ismar.cnr.it). Abstract The Arctic Ocean is the Northern hemisphere heat sink for our planet and is experiencing drastic and fast climatic changes. A major connection between the Arctic Ocean and global climate that has come to the foreground during the past decades is the oceanic component of the global water cycle. Two aspects of the interaction between the Arctic Ocean and global climate appear particularly important. The first involves sea ice and the second involves heat and ocean mass budgets. Considerable effort has been invested in understanding sea ice and the dynamics and thermodynamics of sea ice are probably as well understood as any part of the polar climate system. For example, we know that every year about 3,000 km3 less sea ice was frozen within the Arctic Ocean then is melted, and recently ice melting has increased (Murray et al, 2015). Data about freshwater balance of the Arctic Ocean had been mainly calculated from sea­ice melting and through the contribution of fresh water from land­based glacier runoff after increased atmospheric temperature. The contribution of heat from the ocean and from the oceanographic processes at the interface between the sea and tidewater glaciers has been suggested as a possible trigger destabilizing glaciers’ front. Freshwater input into the ocean and the estimate of seawater properties and movements able to affect submarine melting of tidewater glaciers has been studied theoretically and in situ in several locations (Straneo et al, 2012) and are one of the objectives of ARCA Project. Ocean Heat Content (OHC) is a powerful indicator of climate changes (Levitus et al, 2005), but plain temperature data are more widely used because they are easy to collect and manage and, as a matter of fact, a good indicator. OHC derived from the record of hydrographic profiles and seabed morphology is usually poorly addressed in most of papers on ocean tidewater glacier interaction, including from Kongsfjorden, except one general reference to surface OHC in Cottier et al (2005) and a recent paper by Aliani et al (2016). OHC is defined as the depth­averaged temperature over a given volume of seawater times its density, times the specific heat capacity (eq.1): H = c ρ p V T where = 1027 kg/m ρ 3 is water density, cp = 4000 J/kg◦C is sea water specific heat capacity, V is the volume and T is the depth averaged temperature. The concept of OHC from oceanographic data includes many variables that may locally affect the heat content of a water mass of the ocean and the properties of ocean glacier interaction. It is a global index (Levitus et al, 2005), but at the same time it is very site specific. A snapshot of the spatial differences in OHC between the inner fiord and the ocean at close proximity of glacier interface has been described by Aliani et al (2016) using CTD data collected in September 2014. In this paper, we estimated OHC, calculated as described in equation 1, based on volumes as inferred from bathymetric survey (Aliani et al, 2016) and on temperature time series from Mooring Dirigibile Italia. We used temperature time series over the year 2014­2015 at about 25 m depth, that is the depth where the warm core of Atlantic water has been historically found (Aliani et al, 2004) to infer OHC in the water column. The aim is to explore the seasonal changes of OHC in the Final conference, Rome October 11, 2016