SEASONAL AND INTERANNUAL VARIATIONS OF AMUR RIVER DISCHARGE AND THEIR RELATIONSHIPS TO LARGE-SCALE ATMOSPHERIC PATTERNS AND MOISTURE FLUXES

DOI

抄録

The Amur River, with a basin area of 1.86 × 106 km2, is the fourth largest river in northern Eurasia and supplies much of the fresh water to the Okhotsk Sea, one of the southernmost ice-covered seas in the Northern Hemisphere. The river discharge has two peaks, one in spring and the other in autumn. Freshwater discharge from the Amur River, which causes large stratification that suppresses deep convection and promotes freezing, is an important factor controlling the formation of sea ice in the Okhotsk Sea. Newly obtained observational discharge data reveal the cause of a significant negative correlation between Amur River discharge and Okhotsk Sea ice at multiyear timescales. The annually integrated Arctic Oscillation (AO) influences both summer discharge and winter ice. Summer discharge is larger and winter ice is reduced during positive AO years. Annual AO also influences the annual horizontal moisture flux convergence in the river basin. When the annual AO is positive, the annual mean air temperatures are warm over Eurasia, particularly over the Amur River basin and the Okhotsk. Consequently, autumn SSTs are warmer in the Okhotsk Sea. The warmer autumn SSTs suppress ice formation during the following winter. Freshwater from the river is not the main control of multiyear ice variability. Consideration of the annual AO provides a new look at climate system persistence at multi-seasonal scales. We also investigate the relationship of Amur River discharge and vertically integrated atmospheric horizontal moisture flux by using reanalysis data sets. A northward flux associated with storms in the previous autumn and winter contributes to the spring discharge. The autumn discharge is supplied by a northward flux associated with the Asian summer monsoon and by an eastward flux originating from evaporation in Eurasia. Interannual variation is also investigated. The strong summer monsoon strengthens the summer flux convergence, resulting in anomalously large discharge in autumn. The strong winter monsoon wind with a dry air mass activates evaporation. The anomalously large spring discharge is related to the warm phase of the Arctic Oscillation. These results indicate that the monsoon plays an important role in the freshening of the Okhotsk Sea. This work is partially based on papers by Tachibana, Oshima and Ogi [2008] and Ogi and Tachibana (2006).

収録刊行物

キーワード

詳細情報 詳細情報について

  • CRID
    1390282680669868800
  • NII論文ID
    130007015943
  • DOI
    10.14866/ajg.2009s.0.241.0
  • 本文言語コード
    ja
  • データソース種別
    • JaLC
    • CiNii Articles
  • 抄録ライセンスフラグ
    使用不可

問題の指摘

ページトップへ