1. August 2013 August 2012 NO ICE ‘Flux-gates’ for ice transport 1 2 3 4 CTD location used for average properties Changes in the Beaufort Gyre between August 2012 and 2013. Bill Williams, Fisheries and Oceans Canada, Institute of Ocean Sciences, Sidney, British Columbia, Canada. (Bill.Williams@dfo-mpo.gc.ca) Michiyo Yamamoto-Kawai Tokyo University of Marine Science and Technology, Tokyo, Japan. (michiyo@kaiyodai.ac.jp) Jenny Hutchings, Oregon State University, Corvallis, Oregon, USA. (jhutchin@coas.oregonstate.edu) Rick Krishfield, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA (rkrishfield@who.edu) Sarah Zimmermann, Fisheries and Oceans Canada, Institute of Ocean Sciences, Sidney, British Columbia, Canada. (Sarah.Zimmermann@dfo-mpo.gc.ca) 4: Time series of 0-50m a) Fresh Water, b) Meteoric Water and c) Sea Ice Melt 2: Average properties of the Beaufort Gyre. 3: 0-40m temperature and salinity along 150W in August 2012 and 2013 7: Time series of ice speeds in the Beaufort Gyre Acknowledgements: Fisheries and Oceans Canada’s Annual Joint Ocean Ice Studies expeditions are shared with WHOI’s Arctic Observing Network - Beaufort Gyre Observing System and conducted aboard the CCGS Louis S. St- Laurent. Many thanks to the captain and crew of this ship for their part in these successful missions. On-board sea ice observations were made by Alice Orlich and Judy Twedt for Jenny Hutchings. Timely analysis of Oxygen-18 samples was performed by Jennifer McKay at Oregon State University. Between August 2012 and August 2013 the Beaufort Gyre: - relaxed slightly: the halocline shoaled ~10m and the deep chlorophyll max shoaled ~5m - surface waters became ~0.7psu saltier and carried an O-18 signature of ~1m of ice formation Ice cover was almost entirely absent in August 2012 but there was extensive ice cover in August 2013 that was nearly melted in the south and west (<50cm thick at 70-80% concentration with a large fraction of melted-through melt ponds), and much thicker in the north and east (~127-200cm thick with ~90% concentration). We suggest that these changes were due to anomalous wind: Fall 2012: Weak winds during freeze-up, a time that typically is the strongest forcing of Ekman convergence. February-March 2013: A very large Beaufort High stretched to Siberia. The resulting anomalous westward wind caused large ice export towards the Chukchi and new ice formation in leads leaving a signature of ice formation in surface waters. April 2013 onwards: anomalous eastward wind, during a time that typically has westward wind, held ice in the Beaufort Gyre reducing ice speeds and reducing ice-albedo feedback via leads. The ice ‘melted in place’. Similar anomalously low summer ice speeds with similar ice extent were last seen in 2006. 11: NCEP sea-level pressure for April, May, June and July 2913 8: Fluxes of ice area into the Beaufort Gyre using Fowler/Tschudi ice velocity data. Data is plotted as percent of the area enclosed by the fluxgates. 6: Observed ice concentration and thickness for 2012 and 2013 1: The 2013 AON-BGOS/JOIS cruise track and data locations. 10: NCEP sea level pressure for February-March 2012 9: Zonal wind-stress by month for the NCEP grid points in Figure 1. Westward is up. Black dots are the 1978-2006 average with 2 s.d. error bars. Red and blue bars are the contribution of westward and eastward winds to the average. Mean salinity in 2-40m Depth of 33.1 isohaline Salinity stratification in 5-100m Depth of chlorophyll maximum 10m 5m 0.7psu Low speed in summer in 2006 and 2013 Winter:JFM Spring:AMJ Summer:JAS Fall:OND Winter:JFM Spring:AMJ Summer:JAS Fall:OND Area flux through ‘fluxgate’ 1 Area flux through ‘fluxgate’ 4 APRIL 2013 MAY 2013 JUNE 2013 JULY 2013 FEBRUARY-MARCH 2013 5: Surface properties of the Beaufort Gyre in August 2012 and 2013. SalinityTemperature fSIM fMW fFW fSIM fMW fFW Salinity Temperature fSIM = fraction of Sea Ice Melt, fMW = fraction of Meteoric Water and fFW = fraction of Fresh Water a) b) c) Westward Eastward August 2013 August 2012 Salinity Temperature Salinity Temperature 1 0.5 0 -0.5 -1.5 -2 1 0.5 0 -0.5 -1.5 -2 34 32 30 28 26 24 34 32 30 28 26 24 Latitude