Sea ice thickness is an important climate indicator and is often monitored in the form of freeboard or total freeboard (with snow cover) using satellite altimetry. However, satellites often have a long revisit interval and freeboard measurements in coastal areas can be challenged by land, deformed ice and limited leads. Using a combination of tide gauge for sea level measurements and a coastal GNSS station for sea ice or snow surface height measurements based on GNSS interferometric reflectometry (GNSS-IR), I demonstrate freeboard measurements with high temporal resolution (hourly). In a 4.5-year period from late 2016 to middle 2021, freeboards measured with this method at Cape Roberts, western Ross Sea in Antarctica exhibit a clear annual cycle of ice growth and ablation in the range of ~0–40 cm, and a rapid decrease occurring in Antarctic summer when ocean water temperature increases abruptly. For places where the amplitudes of long-term tides are significantly smaller than the range of annual freeboard variation, GNSS-IR can independently measure both tides and freeboards. Compared to conventional sea ice thickness or freeboard measurements, the tide gauge and GNSS-IR combination method is safe, inexpensive, can distinguish spatial variation of freeboard over a distance of tens to hundreds of meters, and allows continuous monitoring of an area of a few square kilometers.

海冰厚度是一个重要的气候指标，通常使用卫星测高仪以干舷或总干舷（有积雪）的形式进行监测。然而，卫星通常有很长的重访间隔，沿海地区的干舷测量可能会受到陆地、变形冰和有限引线的挑战。基于 GNSS 干涉反射仪 (GNSS-IR) 结合使用用于海平面测量的潮位计和用于海冰或雪面高度测量的沿海 GNSS 站，我演示了具有高时间分辨率（每小时）的干舷测量。在 2016 年末至 2021 年中期的 4.5 年期间，在南极洲西部罗斯海的罗伯茨角用这种方法测量的干舷表现出明显的冰生长和消融的年循环，范围在 ~0-40 厘米，当海水温度突然升高时，南极夏季会出现快速下降。对于长期潮汐幅度明显小于年干舷变化范围的地方，GNSS-IR可以独立测量潮汐和干舷。与传统的海冰厚度或干舷测量相比，测潮仪和 GNSS-IR 组合方法安全、廉价，可以区分数十到数百米距离内的干舷空间变化，并允许连续监测几个区域平方公里。