Radio Echo-Sounding of Spitsbergen Glaciers: Problems in the Interpretation of Layer and Bottom Returns
Radio Echo-Sounding of Spitsbergen Glaciers: Problems in the Interpretation of Layer and Bottom Returns
复制标题
斯匹次卑尔根冰川的无线电回声探测：层和底部回波解释中的问题
作者：
J. Dowdeswell;D. Drewry;O. Liestøl;O. Orheim
摘要1980年使用60 MHz SPR1Mk IV设备对斯匹茨卑尔根冰川进行了机载无线电回波探测。在几个冰川上的结果显示，在440和620兆赫的回声探测中，海底返回的深度是以前苏联回声探测报告的2-3倍。两个冰川的60 MHz记录和独立重力测量的冰层厚度的比较一致在10%以内，而苏联的冰层厚度只有重力深度的30%-60%。苏联冰床的回波往往与SPRI Mk IV系统记录的内部反射层密切重合，结果表明，苏联超高频设备未能穿透到一些冰块(如Finsterwalderbreen、KongsVegen、Negribreen)上的真正冰川床。这可能是由于较高无线电频率的吸收和散射增加所致，这与斯皮茨卑尔根冰川的不均匀性质有关，这些冰川往往处于或接近压力熔点。60 MHz和超高频设备很少在冰盖堆积区(例如Isachsenfonna)记录到床上回声，那里在夏季被积雪浸泡，气温为零度10米。在许多冰川上记录了一个孤立的内反射层。它不太可能是冰漠层，但可能与在Fridtjovbreen钻芯中类似深度(115米)观察到的含水率为1-2%的冰有关。
Abstract Airborne radio echo-sounding of Spitsbergen glaciers during 1980 used 60 MHz SPR1 Mk IV equipment. On several glaciers results showed unambiguous bottom returns at depths 2–3 times those reported in previous Soviet echo-sounding at 440 and 620 MHz. Comparison of 60 MHZ records and independent gravity-surveyed ice thickness for two glaciers agreed to within 10%, whereas Soviet ice thicknesses were only 30–60% of gravity depths. Soviet bed echoes often coincided closely with an internal reflecting horizon recorded by the SPRI Mk IV system, and it is shown that Soviet U.H.F. equipment failed to penetrate to the true glacier bed on a number of ice masses (e.g. Finsterwalderbreen, Kongsvegen, Negribreen). This was probably due to increased absorption and scattering at higher radio frequencies, related to the inhomogeneous nature of Spitsbergen glaciers, which are often at or near the pressure-melting point. Both 60 MHz and U.H.F. equipment seldom recorded bed echoes in ice-cap accumulation areas (e.g. Isachsenfonna), where firn soaking during summer and 10 m temperatures of zero degrees have been observed. An isolated internal reflecting horizon was recorded on many glaciers. It is unlikely to be a moraine layer, but may be related to ice with a water content of 1–2% observed at a similar depth (115 m) in a drill core from Fridtjovbreen.