Freshwater Variability between Ellesmere Island and the North Pole Measured during the Switchyard Project

Abstract:

Between 2005 and 2013, annual surveys of water properties in the upper 700 m between Ellesmere Island and the North Pole were performed each spring as part of the Arctic Switchyard Program. Although there was not a formal Switchyard field program in 2014, the time series was extended to this year with reduced coverage from a combination of stations taken as part of the SCICEX and NPEO programs. The water property measurements were obtained from hydrographic stations taken from aircraft that landed on the sea ice along a line extending between Alert on Ellesmere Island and the North Pole, hydrographic stations taken to the east and west of this line, and moorings located on the shelf and slope regions of Ellesmere Island. Here we report on the measurements made primarily along the north-south section. One of the major objectives of the Switchyard program is to measure changes in the freshwater (FW) inventory and composition in this region. Freshwater inventories were determined from CTD salinity measurements, and the fractions of the primary components of Freshwater [Meteoric Water (MW), Pacific Freshwater (PFW), and Sea Ice Melt Water (SIMW)] were determined by applying the Optimum Multiparameter Analysis method to the temperature, salinity, delta O-18, dissolved oxygen, phosphate and nitrate measurements. During the time of the program there were major changes in the large-scale upper water circulation and in melting of sea ice. In 2009 the Beaufort Gyre weakened, expelling accumulated freshwater, then returned to its stronger state a couple of years later. In 2007 and 2012 there were major sea ice melting events resulting in new record minima of September sea ice extent. The FW inventory along the North Pole – Ellesmere Island line reached a maximum for the study period in 2009 with the increase driven by an increase in MW from 2007 to 2008 and an increase in SIMW between 2008 and 2009. The FW inventory then decreased until 2011 and was roughly constant through 2013. In 2013, MW was at a maximum for the study period and was the dominant freshwater component for most of the section; PFW and SIMW were at their lowest value for the study period and there was no evidence of input from the 2012 sea ice melting event. The 2014 data, which may show shifts in these distributions, is currently being analyzed and will be presented with the earlier data.