Interannual variations of nutrients and primary production over the southeastern Beirng Sea shelf during spring of 1997,1998,and 1999

Transcription

1 Interannual variations of nutrients and primary production over the southeastern Beirng Sea shelf during spring of 1997,1998,and 1999 TaeKeun Rho,Terry E. Whitledge, and John J. Goering Institute of Marine Science University of Alsksa Fairbanks

2 Contents 1. General introduction 2. Results 1. Hydrography across the shelf 2. Nutrients and nitrogen uptake across the shelf 3. Hydrography along the 70m isobath 4. Nutrients and nitrogen uptake along the 70m iosbath 5. Carbon uptake rates 3. Conclusions

3 Bering Sea:sub-arctic ecosystem Consists of a deep basin and a huge continental shelf region

4 Bering Sea:sub-arctic ecosystem Connect to the North Pacific and the Arctic Ocean by passages along the Aleutian chains and the Bering strait

5 Bering Sea:productive in higher trophic levels At least 450 species of fish,crustaceans, and mollusks 50 species of seabirds 25 species of marine mammals Bering Sea fishery contributes over half of the U.S. fishery production Bering Sea pollock fishery: the largest single species fishery in the world

6 Hydrographic domains Coachman et al. 1986

7 Surface currents Stabeno et al Bering Slope Current (BSC) Aleutian North Slop Current (ANSC)

8 Sea Ice NOAA ship Surveyor in pancake ice in the Bering Sea

9 Sea Ice Ice fields in Winter in the Bering Sea

10 Aleutian Low(AL) Cold periods La Nina AL:west weak more sea ice extent Warm period El Nino AL :east strong less sea ice extent January-February Sea Level Pressure Climatology ( )

11 Atmospheric conditions 1997: El Nino Aleutian Low: stronger than normal Calm wind spring 1998 Aleutian Low: similar to 1997 Strong Wind until June 1999: La Nina Strong wind

12 Sea Ice Extents Stabeno et al. 2001

13 Temperatures Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec Hunt et al. 2002

14 Contents 1. General introduction 2. Results 1. Hydrography across the shelf 2. Nutrients and nitrogen uptake across the shelf 3. Hydrography along the 70m isobath 4. Nutrients and nitrogen uptake along the 70m iosbath 5. Carbon uptake rates 3. Conclusions

15 Hydrographic Stations 60 o N Nunivak Is. M4 50m Pribilof Is. 100m M2 Bristol Bay M3 200m Unimak Pass 53 o N 171 o W 159 o W

16 Across Shelf May 1997 Temperature [ o C] M3 M2 Depth [m] M3 Salinity M2 Depth [m] (km)

17 Across Shelf May 1998 Temperature [ o C] M3 M2 Depth [m] M3 Salinity M2 < 32.0 Depth [m] 33.0

18 Across Shelf May 1999 Temperature [ o C] M3 M2 Depth [m] M3 Salinity M Depth [m]

19 Contents 1. General introduction 2. Results 1. Hydrography across the shelf 2. Nutrients and nitrogen uptake across the shelf 3. Hydrography along the 70m isobath 4. Nutrients and nitrogen uptake along the 70m iosbath 5. Carbon uptake rates 3. Conclusions

20 Across Shelf May NO 3 uptake rates (mg N m -3 hr -1 ) M3 Nitrate [µm] ~8 < 2 M2 Depth (m) St.12(SB) St.13(SB) St.23(MS) St.25(MS) St.34(M2) St.68(M3) Depth [m] 15 NH 4 uptake rates (mg N m -3 hr -1 ) Ammonium [µm] M3 M2 Depth (m) St.12(SB) St.23(MS) Depth [m] >10 St.34(M2) St.68(M3) 60

21 15 NO 3 uptake rates (mg N m -3 hr -1 ) Across Shelf May 1998 M3 Nitrate [µm] M2 Depth (m) St.18(M3) St.25(MS) Depth [m] 20 St.27(MS) St.32(MS) St.33(MS) NH 4 uptake rates (mg N m -3 hr -1 ) Ammonium [µm] M3 M2 Depth (m) St.18(M3) St.25(MS) St.27(MS) St.32(MS) Depth [m] 60

22 15 NO 3 uptake rates (mg N m -3 hr -1 ) Across Shelf May 1999 M3 Nitrate [µm] M2 Depth (m) St.02(M2) St.06(M2) St.26(SB) Depth [m] St.38(M3) St.46(M2) St.47(M2) NH 4 uptake rates (mg N m -3 hr -1 ) Ammonium [µm] M3 M2 Depth (m) St.02(M2) St.06(M2) St.26(SB) St.46(M2) St.47(M2) Depth [m] 60

23 Hydrographic Stations 60 o N Nunivak Is. M4 50m Pribilof Is. 100m M2 Bristol Bay M3 200m Unimak Pass 53 o N 171 o W 159 o W

24 Contents 1. General introduction 2. Results 1. Hydrography across the shelf 2. Nutrients and nitrogen uptake across the shelf 3. Hydrography along the 70m isobath 4. Nutrients and nitrogen uptake along the 70m iosbath 5. Carbon uptake rates 3. Conclusions

25 M4 Along Shelf May 1997 Temperature [ o C] M2 Depth [m] M4 Salinity M2 Depth [m]

26 M4 Along Shelf May 1998 Temperature [ o C] M2 Depth [m] <0.5 o C <1.5 o C Cold and less saline M4 Warm and saline Salinity M2 Depth [m] <31.7

27 M4 Along Shelf May 1999 Temperature [ o C] < -0.5 M2 Depth [m] M4 Salinity M2 Depth [m]

28 Contents 1. General introduction 2. Results 1. Hydrography across the shelf 2. Nutrients and nitrogen uptake across the shelf 3. Hydrography along the 70m isobath 4. Nutrients and nitrogen uptake along the 70m iosbath 5. Carbon uptake rates 3. Conclusions

29 Along Shelf May NO 3 uptake rates (mg N m -3 hr -1 ) M4 Nitrate [µm] M2 0 Depth (m) St.34(M2) St.35(MS) St.42(M4) St.43(M4) Depth [m] NH 4 uptake rates (mg N m -3 hr -1 ) M4 Ammonium [µm] M2 0 Depth (m) Depth [m] St.34(M2) 60 St.43(M4)

30 Along Shelf May NO 3 uptake rates (mg N m -3 hr -1 ) M4 Nitrate [µm] M2 0 Depth (m) St.25(MS) St.27(MS) St.32(MS) St.33(MS) St.39(M4) St.40(MN) Depth [m] NH uptake 4 rates (mg N m-3 m hr -1 ) M4 Ammonium [µm] M2 0 Depth (m) St.25(MS) St.27(MS) St.32(MS) St.39(M4) St.40(MN) Depth [m] 60

31 Along Shelf May NO 3 uptake rates (mg N m -3 hr -1 ) M4 Nitrate [µm] M2 Depth (m) St.02(M2) St.06(M2) St.46(M2) St.47(M2) St.11(MN) St.18(M4) Depth [m] 15 NH 4 uptake rates (mg N m -3 hr -1 ) M4 Ammonium [µm] M2 Depth (m) St.02(M2) St.06(M2) St.46(M2) St.47(M2) St.11(MN) St.18(M4) Depth [m]

32

33 Ammonia during PROBES 09 May 1979 Depth (m) 17 May May 1981

34 Ammonium vs. Phosphate Depth (m) Ammonia Phosphate

35 20 Ammonium (µm) June-79(st14-18) Phosphate (µm)

36 20 15 Ammonium (µm) 10 5 June-79(st14-18) June-79(st11-13) Phosphate (µm)

37 20 15 Ammonium (µm) 10 5 June-79(st14-18) June-79(st11-13) June-79(st8-10) Phosphate (µm)

38 20 15 Ammonium (µm) 10 5 June-79(st14-18) June-79(st11-13) June-79(st8-10) May Phosphate (µm)

39 20 15 Ammonium (µm) 10 5 June-79(st14-18) June-79(st11-13) June-79(st8-10) May-97 May Phosphate (µm)

40 20 15 Ammonium (µm) 10 5 June-79(st14-18) June-79(st11-13) June-79(st8-10) May-97 May-98 May Phosphate (µm)

41 Contents 1. General introduction 2. Results 1. Hydrography across the shelf 2. Nutrients and nitrogen uptake across the shelf 3. Hydrography along the 70m isobath 4. Nutrients and nitrogen uptake along the 70m iosbath 5. Carbon uptake rates 3. Conclusions

42 Carbon production: May 97 (mg C m -2 d -1 )

43 Carbon production: May 98 (mg C m -2 d -1 )

44 Carbon Production: May 99 (mg C m -2 d -1 )

45 Conclusions Large-scale climate and local weather conditions the timing of advance and retreat of sea ice and wind mixing events the distributions of salinity and temperature the timing of phytoplankton bloom

46 Conclusions The distribution and concentrations of nitrate shows strong interannual variations due to the timing of phytoplankton bloom the onshore transport the other nutrients (ammonium)

47 Conclusions High ammonium concentrations in early spring may come from remineralization, melting sea ice, and enhancement of microbial loop reduce nitrate uptake rates increase total annual production

48 Conclusions Offshore transport at mid-depth over the outer shelf may important in the export of the middle shelf production to the outer shelf and shelf break region including regenerated Fe

49 Conclusions Carbon and Nitrogen uptake rates show strong interannual variations due to physical conditions and subsequent nutrient availability show spatial variations

50 Future Study Need fine scale study of temporal and spatial distribution of production for better understanding the variation due to the physical fluctuations

51 Acknowledgement Funding agencies for research NOAA Coastal Ocean Program under the Southeastern Bering Sea Carrying Capacity program Cooperative Institute For Arctic Research NSF for the Inner Front Study Travel support from PICES UAF Graduate School UAF School of Fisheries and Ocean Science

52 Thank you

53 Conclusions Large-scale climate and local weather conditions The distribution and concentrations of nitrate shows strong interannual variations High ammonium concentrations in early spring Offshore transport at mid-depth over the outer shelf Carbon and Nitrogen uptake rates