BERING STRAIT NORSEMAN II 2017 MOORING CRUISE REPORT Research Vessel Norseman II, Norseman Maritime Charters Nome-Nome, 7 th July to 15 th July 2017 Rebecca Woodgate, University of Washington (UW), woodgate@apl.washington.edu and the Bering Strait 2017 Science Team Funding from NSF Arctic Observing Network Program PLR-1304052 Chief Scientist: Rebecca Woodgate, University of Washington (UW), USA 1013 NE 40 th Street, Seattle WA, 98105 Email: woodgate@apl.washington.edu Tel: +1-206-221-3268; Fax: +1-206-543-6785 Co-PIs: Patrick Heimbach, University of Texas, Austin (UTA), USA An Nguyen, UTA, USA Related PIs: Kate Stafford, UW, USA; Peter Winsor, Hank Statscewich, University of Alaska, Fairbanks (UAF); Ignatius Rigor, UW (Left: Norseman II, from www.norsemanmartime.com. Right: Little Diomede Island, R Woodgate) As part of the Bering Strait project funded by NSF-AON (Arctic Observing Network), in July 2017 a team of US scientists undertook a ~ 8 day cruise in the Bering Strait and southern Chukchi Sea region on the US vessel Norseman II, operated by Norseman Maritime Charters. The primary goals of the expedition were: 1) recovery of 3 moorings carrying physical oceanographic (Woodgate-NSF) and whale acoustic (Stafford) instrumentation. These moorings were deployed in the Bering Strait region in 2016 from the Norseman II. The funding for the physical oceanographic components of these moorings comes from NSF-AON. 2) deployment of 3 moorings in the Bering Strait region, carrying physical oceanographic (Woodgate) and whale acoustic (Stafford) instrumentation. The funding for the physical oceanographic components of these moorings comes from NSF-AON. 3) accompanying CTD sections (without water sampling). 4) collection of accompanying ship s underway data (surface water properties, ADCP, meteorological data). 5) deployment of an autonomous glider in the southern Chukchi Sea (Statscewich). 6) deployment of two IABP (International Arctic Buoy Program) drifters (Rigor) The cruise loaded and offloaded in Nome, Alaska. Key Preliminary results As discussed below (p.67), the mooring data show some remarkable changes this year, viz.: (i) a remarkably warm June (~ 3 C warmer than climatology); (ii) remarkably early arrival of warm water in the strait in spring/summer 2017 (in hourly data, ~ 15 days earlier than in any prior recorded year and ~ 1 month earlier than the average); (iii) very late departure of warm waters from the strait in late 2016 (in hourly data, more than 20 days later than any prior recorded year); (iv) anomalously fresh waters in winter (~1psu low in winter, ~0.5psu low in the annual mean); (v) a record maximum freshwater flux in 2016, of ~ 3500km 3 /yr (relative to 34.8psu); (vi) record high northward flows in fall 2016 (in 30-day smoothed data). Key Statistics: 3 moorings recovered, 3 moorings deployed, 342 CTD casts on 19 CTD lines Woodgate et al 2017 Bering Strait 2017 Norseman II Cruise report 22 nd July 2017 Page 1:87
PRELIMINARY INTERANNUAL COMPARISONS FROM BERING STRAIT 2017 MOORING DATA Although post-cruise calibrations and extensive data quality control are still to be performed, it is informative to make some preliminary interannual comparisons with past data. 1) From underway data, compared to last year s cruise (which was on the same dates) the strait is remarkably warm already in July 2017. Underway (i.e., ~ 3m/surface) Temperature ( C) from Norseman II 2017 Bering Strait Cruise (7 th -15 th July 2017) Underway (i.e., ~ 3m/surface) Temperature ( C) from Norseman II 2016 Bering Strait Cruise (7 th -15 th July 2016) Woodgate et al 2017 Bering Strait 2017 Norseman II Cruise report 22 nd July 2017 Page 67:87
2) Compared to prior mooring data, we find in 2016-2017: - the strait cooled remarkably late in 2016 (in hourly data, waters above 0 C are found into mid January, ~20 days later than any previous recorded year) (top panel); and - the strait warmed remarkably early in 2017 (in hourly, 7-day smoothed and 30-day smoothed data, waters above 0 C are found as early as mid-may, ~15 days earlier than in any previous year and ~1 month earlier than the average) (middle panel); - 2016 summer season is one of the longest on record (bottom panel). Last day above C after the summer First day above C after the winter Number of days between first and last days above C By year, Julian Day for last day above 0 C (top); first day above 0 C (middle); and length of warm season (bottom) calculated from A3 mooring data, either hourly (red), 7-day smoothed (magenta) or 30- day smoothed (blue). Woodgate et al 2017 Bering Strait 2017 Norseman II Cruise report 22 nd July 2017 Page 68:87
3) Compared to mooring data from 1990-present and the 1990-2004 Bering Strait climatology [Woodgate et al., 2005b], the new 30-day smoothed data show Fall 2016 has anomalously high flows (highest in the record) (top left panel) anomalously high temperatures (comparable to previous high in 2005) and anomalously late cooling (both middle left panel) anomalously low salinities (~ 0.5-1psu less than climatology) (bottom left panel) Early 2017 has above average, but not record extreme, northward flow (top right panel) anomalously high temperatures (~ 3 degrees warmer than June climatology) and anomalously early warming (both middle right panel) anomalously low salinities (~ 1psu less than climatology) (bottom right panel) 30-day smoothed estimates from A3 mooring data for transport (top), near-bottom temperature (middle) and near-bottom salinity (bottom), for 2016 (left column) and 2017 (right column), showing labeled year in color, climatology [Woodgate et al., 2005b] in black, and all prior years of mooring data (1990- present) in grey. X-axis is labeled with month (J=Jan, M=Mar, M=May, J=July, S=September, N=November, J=January). For details of calculations, see Woodgate, [submitted]. Woodgate et al 2017 Bering Strait 2017 Norseman II Cruise report 22 nd July 2017 Page 69:87
4) In terms of annual means, preliminary mooring data suggest 2016 has: Annual Mean Transport ~ 1Sv, viz,, higher than climatology, but less than 2013-2015 Temperature ~ 0.5degC, viz.,cooler than 2015, but as warm as 2007 and 2011 Record minimum salinity, ~ 32 psu, viz., ~ 0.5 psu fresher than climatology High heat fluxes, comparable to previous high years Record maximum freshwater fluxes ~ 3500km 3 /yr (relative to 34.8psu) including a standard correction for the Alaskan Coastal Current and stratification Using preliminary versions of the recovered mooring data, annual mean properties: as estimated from A3 for the Bering Strait: Top - volume transport (Sv); 2 nd - near-bottom temperature ( C); 3 rd - near-bottom salinity (psu); 4 th - (black) heat flux relative to -1.9 C, including (red) standard correction for Alaskan Coastal Current (ACC) and stratification (an additional 1.4-1.7x10 20 J/yr); and 5 th - (black) freshwater flux relative to 34.8psu, including (red) standard correction for ACC and stratification (an additional 800-1000km 3 /yr). Data are corrected for instrument depth changes and known salinity offsets. For discussion on calculations, see Woodgate, [submitted]. Woodgate et al 2017 Bering Strait 2017 Norseman II Cruise report 22 nd July 2017 Page 70:87