Deep-water renewal in a Scottish fjord: temperature, salinity and oxygen isotopes

Abstract

The sea lochs (fjords) of north-west Scotland are located in a region of Europe particularly well situated to monitor changes in westerly air streams. The moisture transported in these air streams has a profound effect on regional precipitation, freshwater run-off and, in turn, sea loch circulation. The gentle slope of the regional salinity:?18O mixing-line, defined as 0.18 ‰ per salinity unit, suggests that the temperature: ?18O relationship may be readily resolved in these coastal waters. Deep-water renewal events, both observed and predicted from empirical models, in the bottom-waters of Loch Etive provide an opportunity to assess the temperature, salinity and ?18O relationship. Predicted changes in ?18Ocalcite as a function of changing salinity (?S) and changing temperature (?T) during deep-water renewal events suggest that >80% fall above analytical detection limits. The theoretical likelihood of recording such renewal events in the “palaeoclimate” record appears to be promising, but temperature and salinity change during renewal events may have either sign. Scottish fjords, because of the relatively small impact which salinity has on ?18Owater, may provide useful study sites in palaeoclimate research, particularly where palaeotemperature is the primary record of interest.